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August 30

Add-ons

My firefox has been slowing down and crashing as of late, so I disabled all the add-ons to see if the problem was with the browser itself. It runs fine without the add-ons, so now I have the task of trying to track down which add-on(s) is responsible for slowing down my browser. I have 40+ add-ons, so how do I go about narrowing it down? 24.189.87.160 (talk) 06:41, 30 August 2010 (UTC)

Add 20 of them back in and see how that goes. Then if ok add half of whats left, if bad remove half of what's there. Etc -- SGBailey (talk) 08:31, 30 August 2010 (UTC)

The good old Divide and conquer algorithm. 213.122.35.55 (talk) 08:42, 30 August 2010 (UTC)

Hebrew font identification

Can anyone help me in identifying the Hebrew font used here? It says רבי מורתי and I think it could be an italic variant... Thanks! ╟─Treasury Tag►senator─╢ 09:46, 30 August 2010 (UTC)

Seems to be partially influenced by Rashi script, but as to the specific font used, I have no idea... AnonMoos (talk) 03:17, 1 September 2010 (UTC)

VB.net

when we creat a project then we want to devloped a setup for it project. How many step invovles to make a project run setup to the help of VB.net? —Preceding unsigned comment added by Manojjnp2010 (talk • contribs) 10:15, 30 August 2010 (UTC)

I'm having trouble figuring out what you are asking. Are you asking for how many steps it takes to make an Installer application for a given VB.Net project? I seem to recall that VB.Net has a pretty automated system from creating a "package" that can self-install (and if need be download the appropriate VB.Net runtimes, make registry changes, etc.) that can be as little as one step if your installation is very simple (e.g. just making sure it ends up in a directory and that they have the VB.Net runtimes). --Mr.98 (talk) 15:35, 30 August 2010 (UTC)

Compare code

Is anyone aware of a tool I could use to compare the source code of two websites. I am doing a bit of research on phishing sites and have came across a fake site, how could I compare the code that is on the fake with with the real site. I suppose I could do it by just scrolling through it but it is a mass of code and wonder is there an easier way thanks Mo ainm~Talk 17:28, 30 August 2010 (UTC)

Download them both with Wget and run Diff on the directories containing the downloads. --Sean 17:51, 30 August 2010 (UTC)

Use fc.--Best Dog Ever (talk) 18:09, 30 August 2010 (UTC)

Notepad can do this. Paste the different source codes you wish to compare into separate tabs, then go "Plugins -> Compare -> Compare" or "Alt + D" 1230049-0012394-C (talk) 19:00, 30 August 2010 (UTC)

Thanks all, I used Notepadd ++ seemed the handiest. Mo ainm~Talk 19:07, 30 August 2010 (UTC)

High x16 PCIe 2.0 Slot-Count Barebone System

Hi.

My current computer is a Tyan FT72B7015 (B7015F72V2R) Barebone System with the following components installed in it.

two Intel Xeon Six-Core X5680 3.33GHz/12MB/130W Processors
eighteen units of Kingston 8GB 1333MHz DDR3 ECC CL9 2R RDIMM x4 with Thermal Sensor (KVR1333D3D3R9S-8G)
four nVidia Tesla M2070 6GB GPU Computing Modules
two Kingston SSDNow V+ 512GB 2.5” SATA II SSD (SNVP325-S2/512GB), in a RAID 1 Array
Microsoft Windows 7 Professional Edition
Microsoft HPC Pack 2008 R2 Workstation Edition

The Tyan FT72B7015 (B7015F72V2R) Barebone System has only eight x16 PCIe 2.0 Slots spaced one slot apart from each other, due to which I'm only able to add a maximum of another four nVidia Tesla M2070 6GB GPU Computing Modules. I'm wondering whether there are any barebone-system(s) currently available which provide atleast ten (preferably twelve or more) x16 PCIe 2.0 slots spaced one slot apart from each other. It would also be very good if the current RAM (Kingston Part No. KVR1333D3D3R9S-8G) and Intel Xeon Six-Core X5680 3.33GHz Processors could be reused on the new barebone-system.

All help and information is appreciated. Rocketshiporion 17:25, 30 August 2010 (UTC)

country ip masking

Is there, and/or will there ever be any way to mask your IP and fool a server into thinking you are from somewhere else without directing your entire data stream through a proxy? Is it even theoretically possible to make a server believe you are from some place, and yet not be limited to the bandwidth restrictions that inherently arise through using a proxy? Thanks. 174.114.145.144 (talk) 18:59, 30 August 2010 (UTC)

It isn't hard. Just use VPN. It is similar to a proxy, but not identical. For example, if I want to access IEEE or ACM papers, I can do it for free if I VPN to one university I have an account with (since they are an engineering school). If I want access to medical journals, I can do it for foree if I VPN to a different (medical) university. My computer's actual IP address doesn't change, but the servers (such as the ACM journal server) thinks that my IP is different. I am, in a sense, using the VPN as a proxy. So, get VPN access to a network in a different country and servers will think you are from that network. -- kainaw ™ 19:22, 30 August 2010 (UTC)

Yes, that's definitely viable; but a VPN is basically a trust-worthy proxy with whom you have an encrypted connection. So you're still technically proxying. You can also use a proxy without encryption, if you so desire. I think the distinction is whether "proxy" is being used as a generic conceptual term, or in reference to specific protocols like SOCKS. Nimur (talk) 21:53, 30 August 2010 (UTC)

In any case, it doesn't sound to me like this is what the OP cares about. The OP doesn't seem to care about security or privacy. They just don't want to be limited to the bandwidth a proxy provides. However there's nothing inherently bandwidth limiting about a proxy. If you pay for a commercial proxy service with a bandwidth promise there's no reason that's going to be more expensive then using a VPN, it could even be cheaper. Clearly you should have no expectations of a public/open proxy or perhaps not even intended to be public/open one.

However as others have pointed out, if the server is smart enough, there's no real way to get around the fact that the server has to see the IP of the proxy at all times, so all the data has to go to the proxy/VPN/whatever then sent on to you so you will ultimately be limited to what bandwidth is available to the VPN/proxy.

In fact a VPN is potentially worse in this case for the OP. I know from experience it's difficult to set up Windows to use different connections for different servers. This means you're going to have all your data going thorough the VPN, as long as you're connected (you can use a different computer or a VM of course), something you may not want and which are of course more likely to create bandwidth problems.

Okay it may be possible to set up if there's a defined subset of IPs you want to be able to access or if the VPN it set up in such a way that it will only grant access to such a subset but even so with a proxy it's IMHO far easier. Just set up one browser to use the proxy, and use that when you want to be proxied, and everything else just goes thorough your normal connection.

Most proxy setups like SOCKS do limit what you can do, e.g. may not be suitable for P2P but again it doesn't sound like this is a problem for the OP. Their only problem/concern appears to be the bandwidth issues.

To put it a different way, if your problem is bandwidth, you need to look for a service, be it proxy or VPN that meets your bandwidth requirements. (If your problem is a proxy isn't working for your app or you care about privacy/security or whatever that's a different matter.)

Nil Einne (talk) 09:35, 31 August 2010 (UTC)

Thanks Nil Einne, you've actually explained exactly my problem. Services like Hotspot Shield "work" for my purposes, I'm not really that worried about security/encryption, but paying for bandwidth is always a problem, and at the speeds that HSS operates at there are a lot of things I can't do. The trend now on the internet seems to be much more restrictive to people living in other countries around the world, but I guess there is no easy solution. 174.114.145.144 (talk) 21:03, 31 August 2010 (UTC)

Dear 174.114.145.144, let me reword your question: Is it possible to receive a reply to a letter you sent off with a deliberately false sender's address on it? See if you can give yourself the answer for that question, and your original question should be answered as well. -- 78.43.71.155 (talk) 19:24, 30 August 2010 (UTC)

You don't have to use a "false" return-address: you can proxy paper mail as well. You just need a trusted agent to do this for you, while maintaining anonymity: e.g., a Post Office box. Like a SOCKS proxy, if the post-office decided to betray your trust, they (the Post Office, or the SOCKS proxy) have the necessary information to make your identity public to a sender; but because you trust that the proxy will not do this, anonymity is guaranteed. You can additionally encrypt your data, so that even if the Post Office (or the proxy server) decides to snoop your mail, the contents are meaningless to them. And you can encrypt the data-path between you and the proxy as well. Nimur (talk) 21:01, 31 August 2010 (UTC)

Some servers only check your location when you first connect, issue you a cookie, and assume all subsequent requests from your browser are from the same location. Clearing cookies and using a proxy, then switching to your standard connection might be enough to fool it into thinking you're connecting from the proxys location for the entire session. 1230049-0012394-C (talk) 19:43, 30 August 2010 (UTC)

Thanks for the answers! I'll see if there's some way I can access VPN. 174.114.145.144 (talk) 21:35, 30 August 2010 (UTC)

usb peripheral switch

I have a "usb peripheral switch". What exactly does it do? It looks like a hub, but apparently it's sort of the reverse? 82.44.55.25 (talk) 20:11, 30 August 2010 (UTC)

Perhaps it allows you to plug a single set of peripherals into the device, and then switch which computer they are connected to.

Similar to a KVM Switch. APL (talk) 21:07, 30 August 2010 (UTC)

Arcade Fire's Wilderness Downtown

Any ideas why I can't get this working in Chrome, using any address? Aaronite (talk) 21:05, 30 August 2010 (UTC)

It could be that the developer of the site did not program it so it would work under any browser. Why not try it with Internet explorer?Sir Stupidity (talk) 00:58, 31 August 2010 (UTC)

I should have been more clear: it was designed specifically for Chrome, and shouldn't work, at least not well, in other browsers. At any rate, it works now. Don't know why. Aaronite (talk) 02:55, 31 August 2010 (UTC)

Hard Drive

I plugged one of my external hard drives into the computer (via usb) and immediately it started making access noises like it was being read/written to. I've disabled the windows search indexer, and anti-virus, yet it makes access noises the moment it's plugged in. I checked with Process Explorer and nothing is showing as reading or writing to the drive. More strange is that even once I "safely ejected hardware" on it, it was STILL making these noises until I unplugged it from the power. The noises it's making sound perfectly normal access noises like if I was copying a large file over or something, it's not weird grinding noises like if it was failing. I can access every file and everything is working as it should. Also it's only happening on this drive. Any ideas what might be wrong? 82.44.55.25 (talk) 22:13, 30 August 2010 (UTC)

Did this happen when you used it for the first timeSir Stupidity (talk) 01:02, 31 August 2010 (UTC)

I've had the drive for a few months, yesterday was the first time it's done this 82.44.55.25 (talk) 10:03, 31 August 2010 (UTC)

Try restarting Windows. If it still does the same thing try it on a different computer to see if it does it there as well. Report the outcomes. --jjron (talk) 15:39, 31 August 2010 (UTC)

I've restarted the computer and it's still happening. I tested the drive on my other computer (Windows XP) and it doesn't happen, so that at least narrows it down to being something going on with my Windows 7 computer. 82.44.55.25 (talk) 19:20, 31 August 2010 (UTC)

Interesting. You could try it on a different Windows 7 computer, just for the sake of it - see if it's an issue with Win7 or just your Win7. If it's troubling you, you could try backing up everything off the disk, reformat it (perhaps using a different computer where it doesn't have this problem, and do a full format, not just a quick format), and then try it again. Maybe someone else has a better suggestion though. --jjron (talk) 07:44, 2 September 2010 (UTC)

August 31

CD ripping -- byte perfect?

Let's say I take a copy of a CD, put it into a computer, and rip it into MP3s using iTunes.

I then take the CD out, put it into an identical or similar computer, and rip it into MP3s using iTunes, with the same settings.

Will the subsequent MP3s be identical? If I made md5 hashes of them, would they match?

I know that obviously if you change the settings, and probably even use different rippers, you would definitely get different results. But what about same rippers, same settings? (I guess you don't even need two computers to test this — you could just rip the same song twice and compare.) Is there some kind of random influence here or would it be identical? --Mr.98 (talk) 00:27, 31 August 2010 (UTC)

The simple answer is it depends on the software used, quality of the CD (whether it's badly scratched or not) and drive. Probably other factors too. Red Book (audio Compact Disc standard) wasn't exactly designed for bit perfect data transmission. For example, it has very limited error correction compared to a mode 1 CD-ROM. During playback, the reader justs reads and usually averages any errors to avoid glitches which works okay if the CD isn't too badly scratched. Not all drives are equally good in how they rip audio. For example some drives don't report errors in the ripping, some even say they don't but don't do it properly. Another problem is that precisely whether to start reading a track is something drives don't agree on. Some even vary from read to read. For this reason, some CRC implementations designed for use with CD audio ignore null samples at the beginning and end, i.e. they only work with the actual audio data. Of course some CDs are semi continuous and the sound from one track flows on to the next in which case this isn't going to help. My impression is drives are better then they used to be and there are good software programs like Exact Audio Copy which will enable you to get generally get bit identical streams compared to 12+ years ago (about when I was first interested in such things). Of course having an unscratched CD also helps. Note that any good (IMHO) CD ripping programme already has some sort of CRC or other double rip comparison function/option built in. There are also databases where you can compare your CRC to user submitted CRCs online e.g. [1]. See also [2] [3] [4]. Nil Einne (talk) 09:12, 31 August 2010 (UTC)

Interesting, thanks. --Mr.98 (talk) 00:54, 1 September 2010 (UTC)

iTunes does not do this sort of checking. For Windows you'd want EAC, as Nil Einne mentioned, for Mac OS you'd want XLD, for other Unixes you could use rubyripper. ¦ Reisio (talk) 02:47, 3 September 2010 (UTC)

Opening image in new tab in same window in Internet Explorer by middle mouse

I am having trouble in opening image in new tab in Intenet explorer by using middle mouse. In mozilla, if I click on image by middle mouse then it automatically opens in new tab under the same window. But in IE 8 it opens in same tab. I want image to open in new tab by using middle mouse. Is there any way to do it?--180.234.22.214 (talk) 00:30, 31 August 2010 (UTC)

Is tabbed browsing turned on in your IE 8? Go to Tools->Internet Options and pick "Tabs" near the bottom of the "General" tab. There you can configure how IE 8 handles tabbed browsing. It has always worked for me, but I do have a vague recollection of having to put a tick in a box to enable tabbed browsing when I upgraded from IE 7 (or was it IE 6?). Astronaut (talk) 10:02, 31 August 2010 (UTC)

Motherboard: The new 'chairman'?

I just got out of a meeting where the person leading it said the word 'motherboard' and then quickly admonished themselves and muttered something about not using that word. I asked around the office here and the opinion from my co-workers is that it's probably some political correctness thing. I've never heard any objections to motherboard before, so is this a new wave of overzealous PC or what?

And yes, I thought about putting this on the Lan. desk but figured there would be more input from IT industry people here. Dismas|^(talk) 00:31, 31 August 2010 (UTC)

I'm pretty sure concerns about the word motherboard aren't new and have existed for 10+ years. It's the primary reason AFAIK why some vendors started using the term Mainboard and that's been going on for quite a while. If anything I think people care less nowadays. I seem to recall Asus made the switch circa 1997 but they seem to have gone back in recent year. Nil Einne (talk) 02:07, 31 August 2010 (UTC)

Wow, that's pretty lame. I had never heard of this. It reminds me of the "controversy" over using the terms "master" and "slave" for IDE hard disks. Comet Tuttle (talk) 15:08, 31 August 2010 (UTC)

Eh, "master" and "slave" are a bit more problematic. (Who minds being a mother?) "Master/slave" smacks of "white dudes named this," whereas "motherboard", I don't know, maybe sounds like "dude named this"? I'm not even sure it's objectionable that the main, important board be the "mother." I don't think I would have a problem with it if it was the "fatherboard." "Master/slave" is an imprecise metaphor anyway. I don't personally find it that much better (or any more convincing) when people say, "but there is also slavery outside of the USA, it doesn't have to be a race thing." Still an ugly metaphor, and not a very good one. There are easier and less leaden ways to indicate that one is in charge of the other. "Boss/Servant" is really no worse, and doesn't invoke exploitation to the same degree, much less the race stuff.

My favorite "PC engineering substitution" was once having to replace every instance of the term "Trip Cock" with "Trip Valve" in a technical manual (designed to be used only by city engineers) in order to conform with New York City municipal standards. Lest we offend the one engineer who will actually reads it and doesn't know that "cock" is a technical term in certain contexts... --Mr.98 (talk) 00:43, 1 September 2010 (UTC)

Wait, also? I'd rather hope there is only slavery outside of the USA, I'm pretty sure you abolished that stuff. To my mind it's a historical term, although I suspect it's not deliberately invoking any concepts about people, but is just carried on from some precedent set by a previous engineering term. Perhaps it comes from hydraulics, where a Master cylinder has slave cylinders. (There is also the engineering term Governor (device), but there's no specific word for the thing it governs, and there are also master and Slave clocks.) Plenty of people mind being mothers - typically because the fathers also mind being fathers, and have taken some unilateral action to address this - but as you say, since the board is an inanimate bit of laminated fiberglass, it's entirely unclear whether the social position implied by "mother" is one of importance or servility. 213.122.52.190 (talk) 08:47, 1 September 2010 (UTC)

Well, prohibition doesn't mean abolishment. There's still slavery in the USA, it's just illegal and we call it Human trafficking now. I know for some people these days, the "slave/master" terms are more associated with D/S fetishists. :) Indeterminate (talk) 16:32, 2 September 2010 (UTC)

Depending on context he may simply have been admonishing himself for using 'technical' words with a non-technical audience. APL (talk) 14:20, 1 September 2010 (UTC)

Preventing Windows Mail from marking email as phishing

I've just begun grad school, and one of the non-scholastic requirements of this program is that I subscribe to a school-wide listserv for announcements. Two of today's emails from professors to us students have been marked as phishing upon arriving in my Windows Mail inbox, for a reason that I can't understand. Is there any way to tell Windows Mail to whitelist all email coming in from a listserv? I've found instructions on turning off the filter and on whitelisting specific email addresses, but I want the filter to keep working, and as many professors and department staff post to this listserv, it would be a waste of time to try to whitelist all of their addresses. Nyttend (talk) 01:30, 31 August 2010 (UTC)

Could you link to the resources you found to whitelist specific email addresses? Nil Einne (talk) 02:20, 31 August 2010 (UTC)

I went into the Help dropdown menu, selected View Help, typed "phishing" (without the quotes) into the "Search Help" bar, and got the results of what I speak. The most relevant page that I found is one called "Security and privacy in Windows Mail", which says that one can create a list of "Safe Senders" to ensure that your friends and relatives don't become blocked by the phishing filter. Nyttend (talk) 02:28, 31 August 2010 (UTC)

I've looked in to this a bit more and I'm not sure if it's possible. Am I right you get a red shield warning you it's phishing? I was wonder if the 'safe sender' thing was just telling you how to set up a filter but it appear it's a specialised function seperate from the Windows Mail filter ('mail rule') option so I don't think you can use this to help. I've looked in the filter options and can't see anything there to help either. If I am correct, the only options I can think of are either use a mail client other then Windows Mail or use Windows Mail but disable the built in filters, perhaps using some other filter addon or external filters if necessary. Nil Einne (talk) 04:58, 31 August 2010 (UTC)

Some lists are also available as digests. While a digest won't arrive in realtime, it usually comes from the same e-mail address, so switching to the digested form of the list, if available, might help. -- 78.43.71.155 (talk) 08:44, 31 August 2010 (UTC)

This list isn't available as a digest, but it's rather important to me that emails come in as soon as possible. Nil Einne, you're right about the message: I get a shield, and every column of text for an email marked as phishing displays as red in the Inbox. It's not a big deal, so if there's no easy way to disable it, I don't think I'll bother. Thanks for the help! Nyttend (talk) 12:19, 31 August 2010 (UTC)

Problem on saving DDS images with alpha

OK, so I'm trying to mod an HUD texture in Mafia II, and whenever I try to save it as DDS, the alpha channel gets borked as 1-bit instead of an explicit one, even if I try to use the DXT5 option. I'm using Photoshop CS3, along with Nvidia's latest DDS tools. Blake Gripling (talk) 02:17, 31 August 2010 (UTC)

Must I retain Acrobat update files?

After upgrading my office computer to Acrobat Standard v9 a while back, I now seem to be accumulating a shitload of files in C:PFAdobeAcrobatUpdate. Standard name is of the form X_modulename_nnn.rtp, where X is mostly the letter H, but some A's and M's too, and nnn corresponds to the release number, 910 for 9.1, 934 for 9.3.4, etc.

By this point, I have up to five copies of each file (with increasing release numbers), taking up a couple hundred megabytes.

Can I safely get rid of all but the latest version of each file?
Having installed the update, and verified that it works, do I even need to keep the latest version?

Thanks, DaHorsesMouth (talk) 02:31, 31 August 2010 (UTC)

It's quite likely that all of these are just temporary files used for installing the update. If you can't find any documentation suggesting otherwise, it might be an idea to back the folder up somewhere, then delete the original. If Acrobat continues to work as before, then you've answered the question - if it stops working, just restore the folder from the backup. ~ mazca ^talk 14:20, 31 August 2010 (UTC)

Error message on XBox

I keep getting error message on my xbox. It says w-0000-0000,x-8000-0013,y-0000-0000,z-0000-0000,ID-FFFF-FFFF. It is on my wireless system and I have tryed two devices. I get on for less than a minute then it go to blimking. To me this all started when they came and made it wpa2p from wep. —Preceding unsigned comment added by 97.113.213.249 (talk) 04:01, 31 August 2010 (UTC)

Does the error message go away if you switch back to WEP? Astronaut (talk) 09:54, 31 August 2010 (UTC)

spam filter "throwing out" political messages

Hi, I have an email account with a big internet company. I support a particular candidate for federal office. I subscribe to the candidate's email newsletter, which I just realized is being put into the spam file. I'll keep an eye out for it, so the problem is solved for me, but is it possible or likely that major internet companies are intentionally favoring some candidates by marking newletters as spam? If so, I want to know. Thanks,Rich (talk) 10:01, 31 August 2010 (UTC)

My first guess is that it is unlikely. A more likely scenario is that something about those emails attracts the attention of the spam filter. For example, many spam filters are suspicious of mails where your address is just one of many in a mailing list. Astronaut (talk) 10:08, 31 August 2010 (UTC)

There are many ways an email can fall foul of a spam filter. Internet and email companies regular check several of the spam blocklists (e.g. http://mxtoolbox.com/SuperTool.aspx ) to see if a domain has been flagged on any of them, besides doing their own filtering on email received. How does a domain get flagged in the first place? Well, they could have sent an email to a Honeypot trap, they could be using too many BCC contacts in their email which their own ISP would then flag as potential spam, they could be the victim of identity spoofing (very easy with emails) which would cause their domain to be wrongly identified as a spammer. There must be many more ways, no doubt someone more knowledgeable will enlighten us further. Zunaid 13:04, 31 August 2010 (UTC)

For mass mailings to pass a spam sniff-test, you need someone writing and sending it that really knows what they are doing. Most of the time political campaigns (especially small ones) are run very cheaply and (no offense intended) with minimal technical talent. Too many hyperlinks and too many spam keywords are a good way to end up in the junk bin immediately. Pushing too many messages at once can earn a spot on a blacklist, and if the email orchestrator for the campaign isn't technically savvy they may not even know what that means or how to remedy it. As far as your theory about content based filtering, in my experience Occam's razor should be invoked; how likely are you to find a company (especially a large one) where everyone has the same ideology to even form a consensus on which side to favor? OK, *except* Fox Broadcasting... --144.191.148.3 (talk) 14:49, 1 September 2010 (UTC)

Very informative. Thanks everyone! Rich (talk) 09:45, 2 September 2010 (UTC)

Processing-Core Price Disparity

Hi Everyone,

I want to know why CPU cores cost twenty times as much as GPU cores. What is it that CPU cores can do that GPU cores can't, which makes soo much more expensive? Please refer to the table below for more information.

Product Name	Number of Cores	Unit Price	Effective Cost/Core
Intel Xeon Six-Core X5680 3.33GHz/12MB Processor	6	$2,400	$400.00
nVidia Quadro FX5800 Graphics Card	240	$5,475	$22.82
nVidia Tesla M2070 GPU Computing Module	448	$8,000	$17.86

Thanks to everyone, reader and respondent alike. Vickreman.Chettiar 12:34, 31 August 2010 (UTC)

GPUs can only process photos and videos, while CPUs can process everything. And it probably costs most to make CPUs than GPUs... Elspetheastman (talk) 12:37, 31 August 2010 (UTC)

Because you're paying for more than just a set of cores. Marnanel (talk) 16:51, 31 August 2010 (UTC)

A Xeon core and a Tesla core are designed for different needs. One of the most important requirements of the Xeon core is high single thread performance. This requires very sophisticated Microarchitecture and circuit design in order to get things done as quickly as possible. And this is very expensive. There are only three companies that have the capability to design Xeon-class CPUs: Intel, AMD, and IBM.

A Tesla core, in comparision, it is very simple, consisting of some execution units, simple (two-way Superscalar, Xeons are four- or six-way superscalar IIRC) dispatch logic, a register file, and misc. interface logic. Because of their simplicity, a Tesla core is not designed for performance, it is designed to be small and to consume little power so a few hundred of them can be placed on a single ~500 mm² chip to exploit massive parallelism, which the Xeon was not intended to do.

Another reason why Xeon cores are more expensive than Tesla cores are differences in circuit design and fabrication. The Xeon, as I mentioned before, requires sophisticated circuit design. That means they'll be designing the Critical paths in Full-custom logic, using circuit types such as Dynamic logic. (Assuming that Intel doesn't synthesis a significant amount of logic first and then optimized it extensively over multiple generations as they did with the Pentium 4, instead opting for lots of full-custom design.) This requires lots of experienced engineers, lots of time and lots of tools. GPUs, I think, are still designed using commercially-available Standard cell libraries. This is easier to design with: it requires less engineers, less tools, and less time. The fact that GPUs have more cores than the Xeon doesn't matter, for both designs, the cores are simply designed once and replicated multiple times.

Differences in fabrication also contribute to the price differences. Intel develops their own process to fabricate the Xeon with. And process development is done in conjunction with circuit design so both teams can optimize for each other. This is expensive. But less expensive than the fact that Intel fabricates the Xeon themselves. This is very expensive. Fabs cost billions of dollars. In contrast, Nvidia uses a commercially-available process from a foundary, in this case, TSMC. They have to buy capacity from TSMC, which shields them from the investment in process technology and the fabs. Another difference is that Intel's process is much more agressive than TSMC's, in regards to things such as features, ect. Process technology is not merely quantified in μm or nm. You can have two 32 nm processes, and one can be 40% slower than the other.

Finally, you ask what can a CPU do that a GPU can't. Many things from a microarchitectural view. For example, a GPU cannot execute instructions out-of-order to help mitigate long-latency events such as division or a load. A CPU can. Another thing is branching. CPUs have very sophisticated Branch prediction, GPUs don't. I am not sure as to the exact reason why, but the way that each GPU core is connected has something to do with that.

This is as many differences as I can think of right now. There might be more, and some of my comments might not be 100% accurate (GPUs are foriegn to me, CPUs less so), but this should be a fair outline of why CPU cores cost more. Rilak (talk) 17:46, 31 August 2010 (UTC)

(ec) "What is it that CPU cores can do that GPU cores can't..." - well, to be blunt, a GPU "core" isn't a "core." It's only an ALU. So when you see a "240-core" count, that's number of EX stages, not number of true "cores." (Well, "core" is weakly defined in computer-architecture, and varies for each type of architecture). Each GPGPU core lacks its own Instruction Fetch, an Instruction Decode, and a proper memory writeback unit. A GPGPU is therefore typically programmed to operate in SIMD mode - so it shares one (or a few sets) of this hardware over the entire chip. In lieu of a per-element decoder, Teslas use a sort of "bitmask" to turn on operations chip-wide or per-thread block. This severely limits what you can program 240 Tesla GPGPU cores to do:: they must all operate in lockstep, because they share the computer hardware that determines what instructions to run. In other words, you can run six different programs on a 6-core Xeon; but you can only run one program on a 240-core Tesla. (In this loose usage, "program" means "unconditional set of instructions"). You basically have 240 copies of the same program. You can read about the basics of Instruction pipelines - like the Classic RISC pipeline - to become familiar with how this works. Modern CPUs like Intel use a extraordinarily sophisticated instruction pipeline - while a GPGPU like NVIDIA's Tesla series use the much more restrictive Parallel Thread Execution pipeline, defined by the PTX instruction set architecture. Nimur (talk) 17:54, 31 August 2010 (UTC)

Like a glorified array processor such as the Thinking Machines CM-1? Rilak (talk) 17:59, 31 August 2010 (UTC)

Yes. But, unlike predecessor array-processors like CM-1 and Cray, ~~CUDA~~ NVIDIA's hardware and software allows "SIMT" - "single instruction, multiple thread" - which does permit much more configurable and customizable programs. This essentially means you can perform different instructions on different subsets of the array. (Though, you really harness the full peak performance of a GPGPU when you treat it as if it were an "old-fashioned" SIMD array-processor with the same exact operation for every point, and carefully manage memory accesses). Nimur (talk) 18:29, 31 August 2010 (UTC)

Google Mail

Resolved

Does google mail delete accounts which have been inactive for a long time? I know Yahoo! Mail deletes stored messages if you don't log in every 6 months, but the account remains usable. Does the same apply to google? 82.44.55.25 (talk) 15:30, 31 August 2010 (UTC)

According to Gmail#Competition "The Gmail system flags as dormant every Gmail account which remains inactive for six months. After a further three months, for a total of nine months dormancy, the system may delete such accounts.". --jjron (talk) 15:49, 31 August 2010 (UTC)

By "delete such accounts", it means that they have the option to delete the email. They do not allow the username to be reused. It remains registered. -- kainaw ™ 19:49, 31 August 2010 (UTC)

Could you clarify, by "delete the email" do you mean they delete all the messages in the account, but the account is still accessible? So even after say, 5 years of not logging in, you could still log in and send messages from that address? 82.44.55.25 (talk) 20:47, 31 August 2010 (UTC)

Jjron's referenced quote is pretty complete. They say "the system may delete such accounts", which means everything in the account is deleted, and since the account is deleted, you would no longer be able to log in. Comet Tuttle (talk) 21:07, 31 August 2010 (UTC)

Ok, thanks. 82.44.55.25 (talk) 21:19, 31 August 2010 (UTC)

SSD Roadmap

Is there any good way to predict the features / sizes / cost of Solid state drives in the near future? Samsung and Toshiba have been making noises about toggle-mode NAND [5], but haven't shipped any actual products yet (AFAIK). I am wondering if this new technology is likely to have a significant impact on SSD sizes / cost during the next 4 months or so, or whether it is more likely to make only a small difference compared to the current technology. Dragons flight (talk) 19:29, 31 August 2010 (UTC)

I don't know much about toggle-mode, but an SSD with nearly identical features is available from Kingston - the Kingston SSDNow V+ 512GB 2.5” SATA II SSDs (part no. SNVP325-S2/512GB). IMHO, the toggle-mode drives will only make a small difference in regard of prices of SSDs. Rocketshiporion 08:01, 1 September 2010 (UTC)

Buying a kindle edition book from amazon

...without owning a kindle? I really don't know much about the kindle, but I'd rather download the kindle edition of Star Maker for five dollars instead of buying it for thirty. Would I be able to still read the book on my Macbook? Thanks : ] ?EVAUNIT^{神になった人間} 21:18, 31 August 2010 (UTC)

Yes. What you need is the Kindle For Mac software. It's free. It's also available for PC, Android, iPhone, iPad, and Blackberry. APL (talk) 14:16, 1 September 2010 (UTC)

Wikipedia:Reference desk/Archives/Computing/2010 September 1

September 2

Compiler Writing: NOT Parser Generators!

I search for compiler writing tools or compiler-compilers on Wikipedia and on Google and when I look at their websites it says they are parser generators (and are used for making domain-specific languages for analysis, not general-purpose languages which I want to do, might I add) and make no mention of compiling SDFs or whatever into compilers! It is driving me nuts. Is "parser generator" just some fancy term for compiler among compiler-writing developers or am I missing something? Is there a good tool out there for Windows that I can use to make compilers (open source, BSD or other permissive license, preferably)? --Melab±1 ☎ 01:04, 2 September 2010 (UTC)

A Lexical analyzer and a parser are two major components of a compiler. The other major component is the logic of what to do with the tokens after they've been parsed. That part will pretty much have to be written by a human.

Luckily for anyone crazy enough to want to do this, this is a common "final project" for C.S. majors, so there are books and stuff on how to do it. (Personally, I opted out and wrote a video game instead.) I make no claims for the quality of either of these two sources (Like I said, I skipped this.) , but this seems to get good reviews, and some folk seem to be very impressed by this older (but probably still mostly valid) guide on the same topic. APL (talk) 02:57, 2 September 2010 (UTC)

Programs are (conceptually) tree-like things, but, because of the human mind's amazing facilities with language, it turns out to be best to represent those trees in a linear fashion, as text, in languages that are (approximately) Context-free languages. Turning the text back into a tree is considered a solved problem (though there's still a little bit of research in that area!), and that's what "compiler-compilers" or "parser generators" do. But a compiler is really something that translates from one language to another, and that part is a classic programming task that's best left in the hands of humans.

There are two things that any prospective compiler writer must think about:

Can an interpreter do the same job? For a lot of tasks, interpreting a language is easier than compiling it, and the speed penalty isn't worth worrying about.
What's the best destination language? Someone has to write a compiler that takes programs to assembly language, but most people don't need to. It's far easier to compile to a pre-existing language with a good implementation. Taking this philosophy to an extreme, the macros in Lisp or (especially) Scheme amount to a tower of gradually-more-powerful languages, each compiled down to the next with an incredibly simple compiler. Common destination languages include C and LLVM, but compiling down to a high-level language like Haskell or Scheme or C or ML is also done.

Paul (Stansifer) 04:25, 2 September 2010 (UTC)

There's no reason you need to re-invent the parser every time you want to invent a new compiler. Parsing is the boring task of sophisticated string tokenization. There's not much to improve or innovate there - it's just a necessary, difficult, and boring part of machine text analysis. Instead of re-inventing this (and similar parts of the compiler), learn to use the already existing Flex and Bison. (Our articles may be the best place to start). These tools do the grunt work of text analysis, leaving the compiler design to you. The real meat-and-potatos of compiler design is the sophisticated process of defining your high-level language into a structured form describable by (for example) Backus-Naur form. That is the first step. Once in this kind of intermediate representation, the second step (mapping BNF to a set of machine instructions) is very pedantic. You should not waste your time re-designing that second mapping (especially if you are unfamiliar with the 900 or so instructions available on a modern Intel CPU, or other CPU architecture of your choice).

Furthermore, using standard tools means that you can plug in your language to existing systems. A lot of compilers for many different languages use the same back-end, so that they can focus on design for their language instead of for the instruction set architecture of the machine(s) they are targeting. For example, almost all of the compiler tools in the Gcc kit (C, FORTRAN, Delphi, Pascal, ... and on and on and on) all use the same gcc back-end structure. This way, your Delphi and your Pascal and your C++ program can all run through the same hardware-optimization routines (and so on). (...totally and irrefutably invalidating any claim about any programming language that inherently yields "better performance" or "faster code" - but I digress).

Anyway, if you really want, you can re-invent these steps; nothing stops you from writing your own parser and lexical analyzer. You can also code a compiler in assembly language; and you can also redefine a Character encoding that uniquely re-interprets machine binary representations as characters of your choice, (ASCII has many shortcomings), and you can write your own text-editor and character-mode video driver that can understand your homebrew text-encoding. There is a certain line you have to draw - decide the tradeoff between how much time you want to spend re-inventing things, and how much time you want to spend learning the existing tools. Nimur (talk) 04:34, 2 September 2010 (UTC)

Responding to your small text: there are many reasons why some languages yield smaller or faster machine code independently of the backend. For example, C doesn't specify the effect of an out-of-bounds array access. This means that an array read or write can legally be compiled down to a single indexed read/write at the machine level. Most other languages require that the index be checked against the array's upper and lower bounds (which must also be loaded from memory) and a certain exception be raised if the test fails. A correct optimizer can't drop the bounds tests unless it can prove they will always succeed (or always fail). In many cases that can't be proven because it's false, and even when it's true, proving theorems is hard even for human mathematicians and it's even harder to program a computer to do it (with useful efficiency). The best you can probably hope for is optimizing away the tests in a simple loop like for (i = 0; i < x.Length; ++i) { ... }, but even that may fail if there's a function call in the body, because it may be hard to prove that the function won't modify x's length. The programmer apparently expects it not to, but programmers are often wrong and optimizers have to preserve program semantics.

There are lots of other examples like this. In an untyped language it's hard to optimize away the extra runtime type checks. In a language with powerful runtime reflection and/or a powerful eval statement, you can't inline any function because you can't prove that it won't change at runtime. In this old thread I listed a few reasons why it's hard to efficiently compile Java and Java-like languages. Aliasing is another interesting example. A C89 compiler must assume that any two pointer expressions of the same type may alias each other unless it can prove otherwise. FORTRAN prohibits aliasing of arrays, which makes automatic vectorization easier. This is one of the reasons why FORTRAN dominated numerical computing for so long. C99 added the restrict keyword to enable optimizations that assume no aliasing. -- BenRG (talk) 23:57, 2 September 2010 (UTC)

Maybe "irrefutable" was an overly-strong word... : ) You are right, and you bring up some cases (like exceptions-handling, and pointer mangling, and function inlining, and garbage-collection) that are language-specific and could limit performance. But for many (actually, for almost any code other than numerical data-processing kernels), these optimizations have minimal impact on wall-clock execution time. The most important optimizations - substituting machine-architecture (ISA) enhancements to replace long streams of common instructions - work on code generated from any source-language. For example, GFortran translates all FORTRAN code to GIMPLE, and then runs the exact same GIMPLE optimizer as it generates machine code, (so whether your program is C++ or Java/gcj, gccwill automatically compile in SSE and 64-bit operations if your computer supports them). So exactly those optimizations you talk about - like handling pointer aliasing and so on, can be handled in a source-language-invariant way (unless the language specifically interferes with these optimizations). Overlapping arrays are the best example of a case where the language-specification will actually enable or forbid certain optimizations (like Out-of-order execution on pointer operations); if the language guarantees these can not exist, the compiler is free to do fancy things. But, outside of sophisticated vector-math numerical kernels, how many programs meaningfully reap the benefit of OOE array operation optimizations? (It should be noted that even Ifort defaults to assuming aliasing - probably because unless you manually specify -fno-alias, it runs through a "C-language" style optimizer that refuses to make the assumption that arrays are "safe", which is specific to FORTRAN). Here's the User Guide for IFORT, with more information than you ever wanted about optimized compilation. Nimur (talk) 00:28, 3 September 2010 (UTC)

Backing-up to a NAS drive over the Internet?

I would like to be able to attach a drive to my mum's router at home so that my computer away at University will be able to back-up via the Internet (updating the back-up to reduce the total file transfers). Is this possible, though? I contacted one or two companies a while ago, and I believe that their responses were that their NAS drives would allow back-up via the local network but not via the Internet. --89.243.142.40 (talk) 01:14, 2 September 2010 (UTC)

I believe that remote access to the NAS is possible, but you will need to configure your router to allow it. First, please note that any changes to the allow outside access into the home network represents a security risk, so you need to make sure that the proper security features (i.e. passwords) are enabled on the NAS device. I assume that your home has a typical network that includes some kind of Modem (cable, ASDL, or similar), which is connected to a Router, which in turn has wired and/or wireless connections to the other devices (computer(s), NAS device, etc.) in the home.

What is commonly referred to simply as a router also provides firewall and network address translation (NAT) features which act as a bridge between your private home network (LAN) and the rest of the internet (WAN). Inside your home network, devices have locally distinct IP addresses typically of the form 192.168.xx.xx, assigned by the router. However, your internet service provider will only assign a single IP address to the model, such as the 89.243.142.40 address we see in your original post. This is the address that the rest of the internet sees.

Normally, any computer inside your private network (or LAN) can initiate a connection out to the internet (the WAN), but any unsolicited attempts from the outside to connect into your network are refused. NAT serves to keep track of what's connected to what, so when one computer sends out a request, the response is routed back to the requesting computer. However, when an inbound connection request is received, the router does not automatically know which local device should receive the request, so the request is dropped. Port forwarding allows you to configure your router to send specific connection requests to specific devices, to send all requests to a designated device (sometimes called the DMZ, or a combination. Port numbers generally identify the type of internet connection request. For example, port 80 is HTTP, which you might want to route to your computer if it were running a web server. Port 21 is generally used for FTP and you may wish to configure your router to forward such requests to your NAS. (You may have already set up some port forwarding if you use some internet games.) You will need to check your router's documentation to see in detail how to configure fort forwarding. You will also need to check your NAS documentation to identify what ports and protocols are supported, and of course how to set up the security.

Port forwarding also allows you to translate port numbers, called port translation. For example, you may wish to map inbound port 8080 to port 80 in your local computer and map inbound port 12345 to port 21 on your NAS. Sometimes this is necessary because many ISPs block certain Well known ports to discourage customers from running home based servers. It also allows you to assign an arbitrary number to the service to make it less likely that a hacker will detect your server using Port scanning techniques.

The final key that you will need is the IP address of the home network. Ideally, it remains static over time, but ISPs generally do not guarantee this, and it may change after a power or service outage. I believe there are some services out there that allow you to periodically post the home's current IP address so that you can look it up remotely, but someone else will need to fill in these details. Once you have port forwarding configured and know the home IP address, you can remotely access the NAS as something like "ftp://89.243.142.40/" or "ftp://username:password@89.243.142.40:12345/" (where "username" and "password" are what you configured in your NAS security setup and ":12345" identifies your externally defined port). From this point you need to look at your backup software to see how to configure it to connect to your distant NAS.

Good luck. I'm sure others can fill in any missing details and correct any error in the above. -- Tom N (tcncv) talk/contrib 04:10, 2 September 2010 (UTC)

I use TeamViewer to remotely access my home PC. It allows file transfers. Not sure it it supports backups as such. ---— Gadget850 (Ed) ^talk 15:37, 2 September 2010 (UTC)

Re: changing IPs above, a simple solution would be to use one of the many free domain name with Dynamic DNS support service. Many routers come with support for updating a dynamic DNS built in, if yours doesn't you can either install software on your mothers computer (should be easier but will obviously only work when your mothers computer is on) or since I believe many NAS devices use some sort of specialised Linux or similar you could probably install something on your NAS (if your NAS doesn't come with it built in, they may I don't know much about NAS). If you're using FTP there may be a bit more work to get it working properly however Nil Einne (talk) 08:40, 3 September 2010 (UTC)

This Type of Image

Kindly have a good look at this type of Image. Please note that my question is not about the format but the style of the image. Such images are perhaps (if I am not wrong) only found on Wikipedia. What I find intriguing as an artist is easy way with which the contrasts of colors is played upon to fool the human eye, which is very-very difficult effect to achieve even digitally let alone with brush. What I'd like to know is what this movement in computer-art is known, what tool is typically used to conjure up this kind of stuff ( I don't think its GIMP). If there is a history behind this movement, i.e. who invented it etc. Are there any Wikipeople out there who are Gurus etc. Jon Ascton (talk) 05:57, 2 September 2010 (UTC)

This is a Vector image; it uses gradient fill (specifically, radial gradients), which are part of the SVG vector image format specification, to define the smooth color blends. This same effect can be done using GIMP on raster-images; though in this case, InkScape was used. The style could be considered Pop art, but it's hard to classify. These images aren't only found on Wikipedia; but this particular image comes from a freely-licensed icon set; so it is advantageous for use on Wikipedia. You can find stylistically similar icons and logos in many other free and non-free projects.Nimur (talk) 06:12, 2 September 2010 (UTC)

I would emphatically dispute classifying it as Pop art, unless you take the perspective that everything is Pop art. A quick look at the Pop art article makes it clear how different it is; it has really nothing in common except a very broad modernist base. --Mr.98 (talk) 11:33, 2 September 2010 (UTC)

Ok, I am not an art critic, so I don't know the definitions well! I see bright colors, bold lines, and stylized cartoonish figures; but if that is not "pop art" in the ordinary definition, then I am mistaken in my classification! Nimur (talk) 20:54, 2 September 2010 (UTC)

Pop art qua Pop art is defined not so much by its appearance as by its intentions. The article discusses this quite well. It's about using the visual language of popular commodities and moving them into a high art context. So it's Andy Warhol painting Campbell's soup cans, as a way of saying, "look, I'm making art by mimicking advertisements," or Roy Lichtenstein making fake "comic book" panels, saying, "look, this wouldn't normally look like art except for the fact that I am blowing it up and claiming it is art," and so on. The general aesthetic I think you are meaning is just modernism more broadly — generally simplistic, often (but not always) basic colors, appeals to function rather than ornate form, stripped down, etc. E.g. Bauhaus or late Piet Mondrian and so forth. I'm not an art critic either, but Pop art is the wrong category altogether. --Mr.98 (talk) 22:14, 2 September 2010 (UTC)

Obviously it is a vector image, and the GIMP and Photoshop specialize in raster images. It would actually be quite easy to draw such an image in an illustration program such as Adobe Illustrator. You draw three squares. Then, you stack them on top of each other and use the Pathfinder palette to make them cut into each other. Then, you go to Effect --> 3D --> Extrude & Bevel. The light above was probably added by drawing a white circle over the shape and then lowering its opacity.

It would be even easier to construct that shape in a dedicated 3D program like Autodesk Maya, where you can add lights. It would look more realistic, as well.--Best Dog Ever (talk) 06:16, 2 September 2010 (UTC)

Which, by the way, would ruin the stylistic effect of that nice icon. Comet Tuttle (talk) 06:26, 2 September 2010 (UTC)

Irrelevant. My point is simple: the drawing is simply three squares and a circle that have been transformed. It is true that it would take a lot of skill for a human to draw that. But it was drawn by a computer. The drawing program only sees three squares and a circle with a list of tranformations. (At least, that's how it would be represented in PostScript after being drawn by Adobe Illustrator.) The work was done mostly by a computer, and it did it with ease.--Best Dog Ever (talk) 06:38, 2 September 2010 (UTC)

This is quibbling now, but saying "the work was done mostly by a computer" is false. This was created by a computer artist who utilized some software as a tool to create the image. Comet Tuttle (talk) 15:22, 2 September 2010 (UTC)

The general look of the image, with its radial gradients and soft beveling, is generally modeled after the iconography that became popular "Aqua" styles used by Apple, Inc.. (see, e.g., their logo, Mail.app icon, Safari's icon). It has since been copied/emulated/improved upon/etc. by Windows (Windows Vista's Aero theme is an obvious descendant), and a number of Linux themes (like the icon you posted there, from KDE). If you Google "Apple icon effect" you can find many tutorials; it is not very hard to accomplish with their a raster or vector editor. --Mr.98 (talk) 11:33, 2 September 2010 (UTC)

See Computer icon, Icon design, and Graphical user interface elements.Smallman12q (talk) 01:09, 4 September 2010 (UTC)

Difference between SIMD and Vector Processors

What is the exact difference between SIMD and Vector processors?

Is there any difference from computation philosophy?

I worked with few processors where 'data parallelism' is implemented by following two methodologies:

(1) Some processors(MIPS, SNE) have some instructions to treat a 32bit register as 'a set of 4( or 2) 8bit( or 16bit) independent elements' and operate over them. Vendors of such processors call it as SIMD.

(2) Some processors(SiliconHive, SPI) have special 256bit registers( vector register) and instructions to operate over these vector registers treating it as 'a set of 16 16bit elements'. Vendors of such processors call it as vector processor

Other than these increased element number, is there any difference between SIMD/Vector processing ?

—Preceding unsigned comment added by ArpanH (talk • contribs) 11:27, 2 September 2010 (UTC)

The terms are generally interchangeable. SIMD is a more specific description of how a processor operates on a vector. "Vector processor" just indicates that the processor is aware of vectors (groups) of data. Since the typical purpose for treating separate data as a single vector is to use the same operation on all of it, most vector operations are SIMD operations. Nimur (talk) 16:09, 2 September 2010 (UTC)

Conventional Explosives Simulation Software

Hi.

Is there any software (whether open-source, freeware or commercial) which can be used to simulate the deformation and detonation of an explosive warhead? This software should be able to accept input of shape, size, dimensions, mass, etc. of both the explosive filler and the warhead-wall; and output the following numerical values.

Total Blast Radius
Lethal Blast Radius
Brisance

The software must support designing with the following 22 explosives:

Mercury Fulminate
Triazidotrinitrobenzene
Triaminotrinitrobenzene
Dinitrodiazenofuroxan
Trinitroaniline
Trinitrobenzene
Trinitrotoluene
Nitroglycol
Tetranitroglycoluril
Nitroglycerine
Mannitol Hexanitrate
Pentaerythritol Tetranitrate
Cyclotrimethylenetrinitramine
Cyclotrimethylene Tetranitramine
Hexanitrohexaazaisowurtzitane
Octanitrocubane
Nitroguanidine
Nitrocellulose
Ammonium Nitrate
Methyl Nitrate
Urea Nitrate
Lead Azide & Silver Azide

Basically, now I'm looking for a free-form explosive warhead design software. Thanks to everyone. Rocketshiporion♫ 12:11, 2 September 2010 (UTC)

r u a terrorist? —Preceding unsigned comment added by Tomjohnson357 (talk • contribs) 13:29, 2 September 2010 (UTC)

You're looking for open source software to design a warhead? I refer you to the answers to your similar question above about looking for open source software to design a nuclear weapon. Comet Tuttle (talk) 15:21, 2 September 2010 (UTC)

He/She wants to simulate an explosion with software. 82.44.55.25 (talk) 15:53, 2 September 2010 (UTC)

If you want to animate an explosion, here are some tutorials: Object Explosion for 3D Studio Max, and Large Scale Explosions for Blender (software). If you want to accurately simulate, then the responses to your previous question still apply. If you really want to research this stuff, consider applying for an advanced technical degree program at a school that studies energetic materials. For example, New Mexico Tech is a science and engineering research university with a specialty in energetic materials. But they won't just hand out information, software, and material support to anybody - because this stuff can be very dangerous. The process of building credibility in these kinds of areas is long and slow and subject to regulation. Nimur (talk) 16:23, 2 September 2010 (UTC)

I should clarify; I already have the relevant information (for most of the above-mentioned explosive compunds) with which to calculate blast radii. I currently have to manually calculate the blast radii based on the RE factor and mass (and shape, in the case of a shaped-charge) of the explosive filler. What I need is just a software into which I can plug the equations for each of the above explosive compounds, in order to automate the process of calculating blast radii, and thereafter animate the explosion. Rocketshiporion♫ 18:15, 2 September 2010 (UTC)

So go use a spreadsheet, then. Masked Booby (talk) 02:45, 3 September 2010 (UTC)

┌��┘
Cyclotrimethylenetrinitramine? You have some pretty potent stuff there...are you looking to make an accurate simulation of this type of military grade explosives? What exactly with and why?Smallman12q (talk) 01:14, 4 September 2010 (UTC)

Mini-flash cookie app

Based on Steve Baker's question above and my reply... Does anyone know of a very tiny flash app that I can put on a web page and then save/fetch cookies through javascript? It would be best if it was a rather invisible little one-pixel app that could be shoved into a corner of the page and not hinder the rest of the page design. The goal is to save cookies in one web browser and fetch those same cookies in another web browser on the same computer. -- kainaw ™ 12:14, 2 September 2010 (UTC)

Be easy to make one yourself; [6] [7] ¦ Reisio (talk) 16:28, 3 September 2010 (UTC)

broadband numbers

my isp gave me these numbers for my broadband

34.2 -15.4 49.8

they said -15.4 was very bad. what do these numbers mean? —Preceding unsigned comment added by Tomjohnson357 (talk • contribs) 13:28, 2 September 2010 (UTC)

Did they really not explain further? The first thing I thought they were were speeds, but I'm not sure. Chevy monte carlo 14:15, 2 September 2010 (UTC)

What's the ISP? From looking at them, I'd guess they're downstream signal-to-noise levels measured in Decibels. 82.44.55.25 (talk) 14:33, 2 September 2010 (UTC)

Yeah, probably. I'm going to guess you have a cable modem, and not DSL. If those are cable modem signal levels, the -15.4 is probably your downstream power level, which is a bit outside the recommended range. If you research it a bit (look up your cable modem model number), you can probably figure out how to check these stats directly on your cable modem's configuration page. DSL modems have transceiver statistics, which look similar, but afaik they don't usually have any negative numbers. Indeterminate (talk) 16:11, 2 September 2010 (UTC)

The poor signal power probably indicates that either you are far away from their networking equipment, or that the cable connection is degraded or has many splits. This is something the cable provider needs to handle; there is nothing you can do about it. Nimur (talk) 16:27, 2 September 2010 (UTC)

Javascript wait

Resolved

I'm trying to write a script for greasemonkey that autofills a box. However the box doesn't appear for 5 seconds after the page loads. Is there a "wait" command in javascript that could pause the script for 5 seconds before continuing? 82.44.55.25 (talk) 18:15, 2 September 2010 (UTC)

Write one function that waits with a timeout and another function that does the work. The timeout requires the function name of the second function and will have the syntax: window.setTimeout("yourSecondFunction()", 5000); // 5000 is how many microseconds to timeout for. -- kainaw ™ 18:18, 2 September 2010 (UTC)

Thanks. What would be the function name of

document.getElementsByName("input")[0].value = "Hello";

82.44.55.25 (talk) 18:52, 2 September 2010 (UTC)

You can place that direction into the timeout as: window.setTimeout("document.getElementsByName('input')[0].value = 'Hello';", 5000); Keep an eye on those quotes. I changed to single quotes inside the double quotes to avoid escapes. -- kainaw ™ 19:10, 2 September 2010 (UTC)

Thanks! 82.44.55.25 (talk) 19:21, 2 September 2010 (UTC)

NP theory

sir, I have been through ur article about NP,NP-Complete and NP-HARD definations and problems but i can't understand the defination of NP-HARD class And the difference between NP complete and NP hard .

What do u mean by "at least as hard as the hardest problems in NP" please explain elaborately !!!!!!!!!! —Preceding unsigned comment added by A khan0001 (talk • contribs) 18:37, 2 September 2010 (UTC)

All NP problems are decision problems. They have an answer: Yes or No. There are many examples. The NP-Complete ones are the difficult ones and they all have the same solution. For example, if I give you a 3-SAT problem, you can rewrite it as a Travelling Salesman problem and then solve the Travelling Salesman problem to solve the 3-SAT problem that I gave you. NP-Hard problems include NP-Complete problems, but much more. NP-Hard is an intersection with NP. NP-Hard includes decision problems and optimization problems. So, consider this: "Is there a way to travel over all the bridges in town without crossing a single bridge twice?" The answer is Yes/No, so it is in NP. It can be NP-Hard also (if it is NP-Complete). Consider this: "What is the shortest route that crosses all bridges in town without crossing a single bridge twice?" The answer is a route, not Yes/No, so it is not in NP. It is an optimization problem. It is at least as hard as the previous decision problem. So, if the original decision problem is NP-Complete, this is NP-Hard. -- kainaw ™ 18:43, 2 September 2010 (UTC)

Wait a minute, not all Yes/No problems are NP, and the "vice versa" part is only formal.

For example, the problem "does a given Turing machine halt?" has a Yes/No answer, but it's not NP. It's not even decidable by a fixed algorithm. See Halting problem.

For the converse, yes, it's easier to do some formal manipulations when you restrict your attention to Yes/No problems, but NP is "morally" more general than that. For example, "factor a given number into primes" is NP in every way except purely formally. --Trovatore (talk) 18:53, 2 September 2010 (UTC)

I was purposely being general because this questioner appears to still be at the "I don't understand the difference between an NP and NP-Hard problem" stage. To many details leads to confusion, not clarity. -- kainaw ™ 18:55, 2 September 2010 (UTC)

Do you think that flat wrong answers lead to "clarity"? Your answer was not even in the right direction; it was not helpful whatsoever. --Trovatore (talk) 19:04, 2 September 2010 (UTC)

Also, factoring into primes is not in NP for two reasons. First, it isn't a decision problem. Second, it is not verifiable in polynomial time because verifying extremely large numbers are truly prime is a difficult problem. The second step of understanding NP that I normally go to is verification of the answer. It must be simple to verify. That is why the halting problem is not NP. If you say "no, it won't halt", how can I verify that answer in polynomial time? -- kainaw ™ 18:59, 2 September 2010 (UTC)

Factoring into primes can be rephrased as a decision problem, in such a way that a polynomial-time answer to one gives you a polynomial-time solution to the other, and vice versa. Something like "given n and k, is the ''kth bit from the right of the smallest prime factor of n equal to 1?".

As for your second point, that's less trivial, but in fact it is now known that it is possible to decide in polynomial time whether a given number is prime. If that weren't the case, we could still talk about "factoring" in general being NP, I think, just not "factoring into primes" (it would require more care in the statement).

Your last point is correct, but you didn't say anything about it in the response to the OP, which made your answer completely useless. --Trovatore (talk) 19:10, 2 September 2010 (UTC)

Actually, for (the decision version of) factoring into primes being NP, you don't need primality testing to be in P. It is sufficient to know that it is in NP, and this has been shown ~~two~~ almost three decades before AKS (and it's much simpler to prove).—Emil J. 10:18, 3 September 2010 (UTC)

Simply put, an NP-hard problem is at least at hard as the hardest problems in NP, but it may be (much) harder and therefore not itself in NP; an NP-complete problem is NP-hard and is in NP. An NP-complete problem is a hardest problem in NP. --98.114.98.162 (talk) 04:32, 3 September 2010 (UTC)

Typing credit card details into SLL-enabled CGI proxies

Is it safe? If not, is creating a bypass proxy a safe way of doing it (as described in this tutorial: http://www.erasparsa.com/Create-Your-Own-CGI-Proxy-to-Bypass-the-Great-Firewall-of-Indonesia). Thanks in advance --Mark PEA (talk) 19:58, 2 September 2010 (UTC)

I only checked the first script on that page, and that one apparently (according to its readme) offered you a form in which you can type an URL. I wouldn't trust any proxy of that type with confidential data. If the other CGIs work the same way - a form, as opposed to allowing you to set it as a proxy server in your browser - they'd be unsafe too. A proper proxy allows your browser to use the CONNECT verb (see Hypertext Transfer Protocol) for SSL, and then simply passes along the data without being able to see it. As long as you verify the SSL certificate and you trust the issuer, and as long as your browser hasn't been tampered with, such connections should then be secure. 82.75.185.247 (talk) 22:07, 2 September 2010 (UTC)

An SSL proxy would mean that the proxy would see your data...the SSL means that the traffic to the proxy is encrypted, but it doesn't mean the proxy is trustworthy.Smallman12q (talk) 01:17, 4 September 2010 (UTC)

Compressing

Resolved

I'm want to compress around 90,000 .mht files. I'm using 7zip with the solid compression option, which works extremely well. I've read about solid compression being susceptible to corruption, for example if one part of the file is damaged everything after it also becomes unsalvageable. Would setting the "solid block" size lower to something like 1GB secure against complete failure? If part of the file got damaged, would only the parts in that "block" be unsalvageable, but files in other blocks would be ok? Is that how sold compression blocks work? 82.44.55.25 (talk) 20:11, 2 September 2010 (UTC)

Yes. If you're worried about corruption, some PAR2 parity files will protect you better than limiting the block size. -- BenRG (talk) 00:03, 3 September 2010 (UTC)

Just make redundant backups. ¦ Reisio (talk) 02:32, 3 September 2010 (UTC)

For such a specific question, I think the best answer to your question is going to actually come from experimentation. Try compressing 1000 files, using two different block sizes, then use a Hex editor to overwrite part of each file with a bunch of random digits, identically, then see what happens when you try to decompress. The experiment won't take long. Comet Tuttle (talk) 15:37, 3 September 2010 (UTC)

I did a few experiments and lowering the block size drastically improves recovery. I also discovered there is very little difference in compression size between full solid mode and 16mb block mode, so obviously 16mb blocks is best the way to go. Thanks! 82.44.55.25 (talk) 18:38, 3 September 2010 (UTC)

Domain Names

Is it possible to find all the domain names that a given company have registered? Thanks Mo ainm~Talk 20:23, 2 September 2010 (UTC)

You could use this Reverse Whois which searches by owner name, but it's not free. It does give you an idea of how many domains *might* be owned by your search parameters (before you have to pay), but there's no real way of being sure that a company is using the same name for all it's domains, sub domains might be registered to smaller sister-companies or there might even be simple things like spelling errors in the owner name when it was registered. Also it wouldn't work with any domains that are using a Domain privacy service to cloak the Whois information as it would literally point to the cloaking service with a reference code and wouldn't contain the company name. ZX81 ^talk 20:59, 2 September 2010 (UTC)

e-mail account hijacked

My wife had her Yahoo e-mail account hijacked today. Apparently everybody in her address book (except me) got a message saying she had been robbed and was stranded in London airport and could you please wire £1500 immediately. As soon as she was able she went in and changed the password and security questions in her account.

This doesn't appear to be e-mail spoofing; one friend wrote back and asked the perpetrator for the names of two dogs. In the response one answer was actually right (our daughter's dog, dead for three years).

The question is: what happened? Did someone actually get into the account? She said some profile fields were changed. If so, how could that have happened? Did they get the password? Also, having changed the password, how safe is she now? Thanks, --Halcatalyst (talk) 22:31, 2 September 2010 (UTC)

Some possible reasons are:

she used the same password for something else, or the password was something too obvious (the name of her kid, or dog, or favourite band)
her password was too poor, and a bulk script (probably running on a botnet) guessed it
she left herself logged in on a public machine (e.g. at the library)
her normal machine is compromised by malware
she logged in on another machine (web cafe, library) which was compromised by malware
she used an insecure login method (yahoo! mail does login by default over ssl, so that'd be an odd reason) over a public wireless network (e.g. at a cafe)
she donated, lost, or had stolen a computer, pda, phone, or backup, and someone recovered the password from it (this is quite possible, but in practice fairly unlikely)
she got a crooked email, or visited a crooked website, which directed her to a site constructed to closely mimic Yahoo! Mail, but that was in fact the spammers'.

They probably know the name of the dog because they searched the email account for "dog" when interrogated.

Sensible things to do:

have a genuinely secure password
don't use the same password for multiple things (except for trivial things that you don't care about, and definitely don't use the trivial-things password for something important like shopping, banking, or email)
just don't type your password into a public machine at all, or into any machine you don't absolutely trust. If you need to be mobile, setup a phone or laptop to check email, and use that.
make sure you use SSL for login
keep your own computers properly maintained, with up-to-date and effective anti-virus and anti-malware software. Practice caution when installing software. Don't allow incompetent people or those with poor judgement the ability to administer the same machine you use for work, banking, or an email account that you've registered with anything important (if they control the email, crooks can have shopping or banking sites reset your password, which is emailed to them, so they've leveraged email access into something more valuable).

-- Finlay McWalter ☻ Talk 23:07, 2 September 2010 (UTC)

Another wise thing: only visit an important site like email or banking from a URL you typed in yourself, or from a link you've stored on your own computer (e.g a bookmark or a desktop shortcut). Never click on a link on some site that purports to take you to Yahoo!Mail, in case it's a malicious spoof instead. -- Finlay McWalter ☻ Talk 23:24, 2 September 2010 (UTC)

And (just to scare you more) they might have done something like this (all with a script, all very fast, trying many many options):

get access to the email account (by some method above)
search the email account for mails from financial institutions (FIs) - banking, pensions, stocks, investments
from these, visit the FI's website and try to login with the password they know. If that fails, do a password-reminder
the FI emails the Yahoo! account the reminder or temp-password, which they use to login. Only the security questions are stopping them now: how good are her answers? Is her pet's name given as "Fido" or "h!fP9+3J>Q7"? If they have access to the email account, they can search it for clues (pets, kids, favourite places)
transfer monies away
delete the password reminder email(s) to cover their tracks a bit (even a few hours will be enough for them to forward the stolen money on through a maze of compromised or untraceable accounts).

-- Finlay McWalter ☻ Talk 23:18, 2 September 2010 (UTC)

She may also have somehow visited a "Phishing website" that appeared to be a Yahoo login screen, but was REALLY just a false front that sent her password to the scammers. (It may have actually forwarded her to the real Yahoo website so she wouldn't notice anything was wrong.)APL (talk) 02:24, 3 September 2010 (UTC)

September 3

Idiotic and Useless Emails

Why I keep on getting more and more foolish messages like proposals to get quick money (100000 $) ! etc. from a bank etc. who account holder is dead or other bullshit like that. Who is behind all this and what they gain by wasting people's time ? Jon Ascton (talk) 01:11, 3 September 2010 (UTC)

Have you ever heard of a Phishing trip? (Now that I read that joke a couple times, it sounds really corny...) Essentially, some slob sitting in a smelly apartment somewhere is hoping you're dumb enough to hand over your most sensitive financial information. Then, they can then use it to ring up something expensive and/or illegal, or sell it to someone else who will end up doing that anyway for thousands of dollars. Of course you wouldn't hand over your credit card number for no good reason, so they cook up all sorts of crazy schemes to dupe you. Most often I hear about the Nigerian prince scam that asks you to wire money to a sketchy Nigerian "prince" so he can send you a ridiculous amount of money in return. Other suspicious e-mails include: you have won a lottery you never entered, and the company needs your bank details so they can send you the winnings; the legitimate-looking e-mail from your bank telling you that you have to change your bank website password for some reason; or there is some rich foreigner who died in a plane crash with no will or family, and you have been chosen to receive his fortune. Ignore them. It's a huge business, and many people are suckered in. You can protect yourself by just deleting them, and remembering that there is no such thing as free money. Xenon54 (talk) 02:14, 3 September 2010 (UTC)

Or set up a filter that puts mail with words like 'free money' into junk.Sir Stupidity (talk) 03:22, 3 September 2010 (UTC)

There are several of these scams out there and people fall for them every day. I read an article a couple years ago about a woman who kept giving more and more money away to someone on the net in the hopes of an eventual pay off. If I remember correctly, she gave the scammer something like US$14,000. Dismas|^(talk) 04:38, 3 September 2010 (UTC)

There was an elaborate scam attempt on me the other day. I offered a cellphone for sale online in South Africa, and this person claiming to be on holiday in London wanted me to post the cellphone to his son working in an oilfield in Nigeria. Just the mention of Nigeria set off an alarm bell and I refused to give him my banking details... he even offered way more money than I was asking. Obviously this sounded too good to be true so I told him to transfer into my paypal account. Soon after I got a very authentic looking email from "paypal" but first of all, my paypal status wasn't updated and after looking at the email more carefully, I noticed the odd spelling mistake and the wrong email account being used. It was also sent by someone@gmail on behalf of services@paypal. I reported it to paypal who said they would investigate. I can imagine some derelict warehouse in Nigeria receiving thousands of free items a day and the police there just turning a blind eye. Just be careful people... even worse than material theft is identity theft... it can wreck your life. Sandman30s (talk) 06:00, 3 September 2010 (UTC)

The basics of the scam have already been clearly outlined. The scammers work on a model that expects a tiny fraction of people that fall for it - The vast majority of people will simply delete the email. However, as in the case mentioned by Dismas - when the phishers do get a 'bite' they can be in for a significant prize. If it really does annoy you, there are a number of sites set-up that give advice to people about trolling the scammers, and they also publish transcripts of the trolling communications (some can be quite funny). If you do go down that route though, be careful not to give the scammers any personal information that could be used to steal your ID Darigan (talk) 11:23, 3 September 2010 (UTC)

So why do you keep getting these foolish emails, while I haven't received any spam in months? Because I don't go spreading the email addresses I really care about all over the internet. I tell friends and relatives my real email address, I use several webmail accounts for signing up to site memberships and shopping (places that might sell my address onto a third party), and I use other webmail accounts for very occasional 'dodgy' dealings with places that will definitely sell my address onto a third party. Also, I never reply to any spam, even to request they 'unsubscribe' me. The net result is that the spam ends up in an account I only visit once or twice in 6 months, and my real address gets no spam. Astronaut (talk) 11:39, 3 September 2010 (UTC)

It's really important never, ever, to reply to spam. There is a possibility that a spammer receiving any sort of reply could make him notice that the e-mail address is live, which encourages him to send even more spam to it. Because of a similar reason, the e-mail client I use (Evolution) by default does not automatically download images in HTML e-mails. If it did, the spammer's HTTP server would register a connection from my IP address, confirming that the spam was received by a live person. So Evolution is clever enough to prevent that. JIP | Talk 19:16, 3 September 2010 (UTC)

data corruption

Resolved

Is there a way to simulate data corruption on a file? Like a special program that can corrupt a file to varying levels so you can test how much the data is retrievable? 82.44.55.25 (talk) 09:47, 3 September 2010 (UTC)

A Hex editor may be the simplest to use for your basic tests. If you want to be systematic, a simple program should be easy to write; you just have to define "corruption". For example, consider three different kinds of failures:

"zero out 1 byte at 1024 uniformly-distributed random locations in the file"
"zero out 1024 bytes, starting at file-offset 100,000."
"zero out every 8th byte, starting at file-offset 0, and ending at file-offset 8192"
"Xor 1024 bytes in the file using the same bitmask."

These all corrupt the same number of bytes in file, but each simulate a different kind of failure-mode. Unless you know how your files might get corrupted, it's difficult to simulate (or to design a good strategy for recovery). Consider reading our Error detection and correction article. Nimur (talk) 18:06, 3 September 2010 (UTC)

Thanks! 82.44.55.25 (talk) 18:35, 3 September 2010 (UTC)

Parchive

I've read the Parchive article but I don't understand how it works. It makes indexes of file hashes which can be used to repair files? How exactly is that done? What level of damage can the file be before the Parchive can't fix it? 82.44.55.25 (talk) 09:56, 3 September 2010 (UTC)

It uses a Parity bit system. Parity relies on Xor which is a bit operation. Just like addition is 1+1=2 and represented by a +, xor is a bit operator and is often represented with a ⊕, or a ^ in some programming languages. Xor is "one or the other but not both." So 0⊕0=0, 1⊕0=1, 0⊕1=1, 1⊕1=0.

If you're storing something, let's say a string of 1's and 0's (1100 0010). You can split it up into two blocks, then compute a third block, a parity block. So you then store 1100, 0010, and 1110 (the last one is your parity block). Now if any one block gets clobbered somehow, you can figure out what it was using the remaining blocks. If two or more get clobbered, you're out of luck.

This is the general idea. It can be expanded, applied to millions of strings like that, etc. That's how parity systems work. You might find RAID-5 interesting, it works on the same principal. Shadowjams (talk) 23:20, 3 September 2010 (UTC)

I want to point out that my explanation isn't exactly how parchive works either. It uses Reed Solomon codes which entail more detail. [8] That is the original paper that the theory's based on. But the general idea is still the same. Shadowjams (talk) 23:36, 3 September 2010 (UTC)

Webpage to PDF

Is there anything that can easily turn a webpage into a PDF? I have seen the the Firefox add-on 'PDF Download' but it is tagged as Adware, does the conversion online, and has had bad recent reviews. Thanks 92.15.11.118 (talk) 10:17, 3 September 2010 (UTC)

My Firefox allows me to print (File -> Print) to a file, and I can select PDF as the output file. Does this suit you? --Ouro (blah blah) 11:13, 3 September 2010 (UTC)

My computer (WinXP) does not offer that unfortunately. 92.15.11.197 (talk) 14:04, 3 September 2010 (UTC)

If you want something that can do it in batch (for example to snapshot a website regularly) wkhtmltopdf works well.-- Q Chris (talk) 11:23, 3 September 2010 (UTC)

That looks interesting but as Windows has deskilled me so that I only understand clicking something, I do not know how to set it up or run it. 92.15.11.197 (talk) 14:08, 3 September 2010 (UTC)

For this purpose, I installed CutePDF Writer, which does the same thing that Ouro above describes on my Windows XP system. Comet Tuttle (talk) 14:56, 3 September 2010 (UTC)

In an unexpected turn of events, I cannot check how it works, no Linux version. Sidenote, I wonder why FF for Win does not give the option to print to a PDF file. Hope Comet's solution works out for you. --Ouro (blah blah) 16:23, 3 September 2010 (UTC)

"print to file" is part of the standard desktop printing architecture in many desktop Linux distributions. It works just the same as the pseudo-printer that CutePDF installs. It's available to any desktop program that's aware of printing (strictly I think there's one plugin for Gnome and a different one for KDE, but they work much the same); they're mostly a layer built on Ghostscript. Non-gui programs have to call Ghostscript themselves to do the same job. -- Finlay McWalter ☻ Talk 16:33, 3 September 2010 (UTC)

Could be. Has to be out of the box, this install is fresh (done last week) and almost nothing had been modified because I didn't have the time to do it. On Ghostscript, I remember yeaaaaaars ago (in the days of W98SE) I had to install Ghostscript to do... a lot, print to files too I think... Thanks. --Ouro (blah blah) 16:39, 3 September 2010 (UTC)

I use PDFmyURL. It does exactly what it says on the tin - type your URL into the box and it provides a PDF to download. It does add a logo to the PDFs though. Equisetum (talk | email | contributions) 17:15, 3 September 2010 (UTC)

a/b drives

why do my computer does'nt have a, b drives —Preceding unsigned comment added by Shantanuca (talk • contribs) 10:43, 3 September 2010 (UTC)

These are usually assigned to floppy drives. If your computer doesn't have a floppy drive, then those drive letters won't be shown 82.44.55.25 (talk) 10:57, 3 September 2010 (UTC)

See Drive letter assignment. It's sad that people are already forgetting floppy disks; it makes me feel old. In any case, what happens if you have more drives than letters to assign? Do you start getting drives AA, AB, etc., or does the computer just not let you do it. Buddy431 (talk) 13:28, 3 September 2010 (UTC)

I asked a question about that a while ago, Wikipedia:Reference desk/Archives/Computing/2010 May 2#Drive_letters 82.44.55.25 (talk) 13:42, 3 September 2010 (UTC)

That's interesting, thanks. Buddy431 (talk) 01:17, 4 September 2010 (UTC)

Javascript time

I want to write a greasemonkey script that will popup an alert box at a certain time, say 6pm. Sort of like an alarm clock. In javascript, is there a way to make a function execute at a set time? 82.44.55.25 (talk) 11:08, 3 September 2010 (UTC)

The window.setTimeout function will launch a function after a specified number of milliseconds. Calculate the number of milliseconds between now and 6pm. Then, use that number of milliseconds as the offset for setTimeout. -- kainaw ™ 12:43, 3 September 2010 (UTC)

Cell Phone and Lap top

I am thinking about purchasing a cell phone and contract that will allow me about 800 anytime minutes free on weekends and evenings. (perhaps a variation, free incoming) I also want to be able to retrieve email and brouse Web. I can get such a plan for about 60.00 a month. I would then like to cancel my home internet and home phone. I only want to do this if I can plug in the new phone to my lap top and be able to read my email on the lap top and to hopefully write emails on the lap top that will be sent back through my cell phone. DOES ANYONE KNOW IF THIS IS POSSIBLE. ANY ADVICE IS APPRECIATED. I AM GOING OUT TO DO SOME HANDS ON TESTING BUT HAVE NO IDEA WHAT WOULD BE THE BEST PLAN OR PHONE. I DO SEEM TO FAVOUR THE SLIDE KEY BOARD FOR TYPING TEXTS. A bigger phone screen would also be helpful for reading texts etc. —Preceding unsigned comment added by 99.199.47.107 (talk) 17:06, 3 September 2010 (UTC)

Where are you? Your IP address suggests you're in Canada. -- Finlay McWalter ☻ Talk 17:21, 3 September 2010 (UTC)

What you're wanting to do is called Tethering. Most smart phones can do it in some way or another. You will want to check with your mobile provider to see what options they offer for mobile broadband tethering. Most mobile broadband plans are designed with the idea that access is solely through your phone. Thus, most providers charge extra for this service. Also, keep in mind that mobile broadband plans are usually more restrictive in terms of bandwidth and data caps. If you're just utilizing the Internet for email, you shouldn't have a problem. However, if you're wanting bandwidth intensive applications (video, gaming, etc.) you are going to see poor performance compared with wired Internet access. --—Mitaphane _{Contribs | Talk} 18:31, 3 September 2010 (UTC)

Methods for multiple classes

I'm trying to write a math thing in Java where there is a fraction class, a radical class, a polynomial class, and so on. When defining multiplication for fractions, I would multiply the numerator and the denominator, but there could be many things in the numerator, like an polynomial or a radical or something. First, how would i declare the class of the numerator, and second, could i write something saying "call the multiply method of whichever class this belongs to"? KyuubiSeal (talk) 21:44, 3 September 2010 (UTC)

There are several ways you can do this. Off the top of my head:

You just have each type of math thingy implement multiply functions for all the things it's meaningful to multiply it by. Java's polymorphism mechanism will call the right one. So your Complex class might have a multiplyBy(Integer) method, a multiplyBy(Complex) method and so forth. This is the straightforward way to go - a (probably minor) downside is that if you add a new kind of math thingy you need to alter all the things it can multiply by so that they know about it, and you have to do that at compile time.
If you needed extensibility beyond that, you can dispatch calls through a dynamic registry you maintain. That way you can add (even at runtime) new math thingies, but the code gets rather complex. Have all these math thingies be concrete implementations of an abstract base class (lets say MathThingy). MathThingy has a multiply(MathThingy A, MathThingy B) method. This is final. When this is called, it uses getClass on its arguments, looks them up in a little registry, and calls specific methods in the concrete subclasses. The registry is filled by the class constructors of each MathThingy as they're classloaded - so the Complex class registers handler methods that say they can handle intXcomplex, complexXint and complexXcomplex. This is very flexible - you can even add new operators (at a logical level; java doesn't allow you to overload or define actual java syntax operators). But a major downside (aside from the complexity) is that type errors become runtime errors rather than compile time ones (so you don't get a problem saying you can't raise a complex number to the power of a matrix until you run the program).

-- Finlay McWalter ☻ Talk 22:08, 3 September 2010 (UTC)

I get the first part about the polymorphism already, but I suppose I should rephrase my question. If I have a Fraction class, it would have an attribute numerator, right? How could I make the numerator an instance of the Polynomial or Radical or BigInteger class? And when it is, is there a way I could say numerator.multiply(5), and have it call the correct class's multiply(int)? Also, how is there no operator overloading, but "a"+"b" will give "ab"? Is that just a special case? KyuubiSeal (talk) 23:07, 3 September 2010 (UTC)

In your example, you need "Polynomial or Radical or BigInteger" or "..." to satisfy either option:

implements a common interface, like "Multipliable", or
extends a common parent class, like "MathematicalExpression"

The first way uses a Java interface, and you can follow this tutorial to learn how to use it. The second method uses inheritance - follow this tutorial to learn how to use it. The two methods are subtly different. Now, you can specify your numerator to be a "Multipliable" or a "MathematicalExpression" - and any class that either implements that interface (or extends that parent-class) is acceptable to use as a Numerator. Then, when you call a multiply() method, it will use the implementation of that method for the actual runtime type of the object. Nimur (talk) 23:33, 3 September 2010 (UTC)

Lastly, your question about Strings: these are "special things" in Java. Consider them a "special case" - they are true objects, but they are the only objects in Java that permit Operator Overloading (and this is the cause of much debate and brouhaha - but was part of the language design). Note that the language explicitly specifies this syntax - and it is not actually "operator overloading," it is special shorthand Java syntax for a new String constructor. This is to make the language "easy to use" for text processing, while staying true to certain "Java commandments" about object-oriented design. (And, take it from a seasoned programmer: you do not want operator overloading. You think you want operator overloading, but that is because you don't have it and haven't seen how horrible it is). Nimur (talk) 23:40, 3 September 2010 (UTC)

(we're rat-holing here, so I won't belabour this too much) when people say they "do not want operator overloading" I've found they mostly mean the brain-damaged operator overloading that C++ inflicts on innocent minds. Haskell's operator definition (I won't insult it by calling it overloading) lets you define type, arity, priority, and fixity (and actually deigns to let me define any operator I want, like foo or ⊕ or !!!) and combined with Haskell's non-shit type system makes for operator definition to work the way you'd sanely want it to. Sorry for the digression, as KyuubiSeal is working in an environment without such luxuries. -- Finlay McWalter ☻ Talk 01:12, 4 September 2010 (UTC)

So if I have a variable of class A (or interface B), any subclass of A (or something implementing B) can be assigned to it? This means anything can be assigned to an Object, right? And would there be any casting involved? (That's probably not too difficult to handle though) KyuubiSeal (talk) 23:55, 3 September 2010 (UTC)

Yes, you can assign an object of a subclass to a reference of any of its superclasses. And the system remembers what type it really is - so if you later upcast it (Java will make you handle a ClassCastException in this case) it's still of the same type you defined it as. The java instanceof is your friend here - you can say "is X an instance of A, or is it an instance of B, or not", and act accordingly. -- Finlay McWalter ☻ Talk 00:57, 4 September 2010 (UTC)

Okay, it's working now. Thank you so much! KyuubiSeal (talk) 01:09, 4 September 2010 (UTC)

Terminal window of safari

Where can I find the terminal window of Safari 5.0.1? I want to do some tweaking.Thanks--180.234.39.169 (talk) 23:22, 3 September 2010 (UTC)

Safari does not have a terminal; are you sure you don't mean either the operating system's terminal or the Safari Snippet Editor or Error Console ? Nimur (talk) 23:26, 3 September 2010 (UTC)

How can I open terminal window?--180.234.39.169 (talk) 07:25, 4 September 2010 (UTC)

If you mean your operating system's "terminal" window, try to navigate to /Applications/Utilities and double-click on Terminal. If you still can't find it, see this.--Mithrandir^∞(Talk!)(Opus Operis) 07:31, 4 September 2010 (UTC)

September 4

Recovery of Deleted File on SD Card

Help!

I accidentally deleted a .zip file from a Secure Digital card. The file is about 275KB in size, and was deleted before a backup could be made. In order to stop the deleted data from being overwritten, I have made the SD card read-only by using the write-protect switch. The SD card's filesystem is NTFS, and my operating-system is Microsoft Windows 7 Professional Edition. I need to recover the deleted file ASAP - is there any free software or freeware I can use to recover my deleted file?

Any and all help is appreciated, and thank you to everyone.

I don't know offhand what the windows software is but there is Linux software to do the same thing. There are Live Discs that do the same thing. It's likely your file's recoverable. Write protecting it is the right idea. I'm sure others will know of some windows software. Shadowjams (talk) 07:13, 4 September 2010 (UTC)

PhotoRec and Recuva both come highly recommended and can undelete basically anything as long as it hasn't been over-written. Good luck! Zunaid 07:17, 4 September 2010 (UTC)

What is the cellular 3G base station price range?

If someone want to cover around 5,000 km2 with 3G coverage - what amount of investment into cellular hardware he will be looking at? Assuming wired data network is already exist and installation costs for towers are out of scope of this question(and spectrum licenses out of scope too). One million users inside 5.000 km2. Basically, how much one base station roughly cost and how big would be the cell it will cover? Was trying to search Google, but no luck so far. —Preceding unsigned comment added by 70.52.186.74 (talk) 07:31, 4 September 2010 (UTC)

I don't know about the cost, but the number of base stations would depend on the specific mobile technology and frequency used, the local geography and the amount of bandwidth required. The table in this article suggests a CDMA-2000 network operating at 1800 MHz has cells 14 km in radius (each covering an area of ~600 km²). However, considering how close the mobile masts are in my area of the UK, I think that might be an idealised radius. Indeed, OFCOM's Mobile phone base station database indicates that a city of 100,000 people has well over 50 base stations and a city the size of Manchester has nearly a 1,000 base stations. Astronaut (talk) 08:46, 4 September 2010 (UTC)

Scanning over the network

The charity where I volunteer recently bought a new printer/copier/fax/scanner (a Xerox Workcenter 4118). It has a builtin network card which is connected to the rest of the network using a standard ethernet cable, and a standard telephone connection is used so faxes can be sent and received. However, reading the user manual it seems the scanner function can only be used if it is connected a USB or parallel cable. Is there a way to get scanning to work across the network using any PC on the network, perhaps using a third-party piece of software? Being an underfunded charity, there is a strong preference for a low price, or better still, free solution. Thanks. Astronaut (talk) 08:12, 4 September 2010 (UTC)

Go to Start --> Control Panel --> Scanners and Cameras --> Add Device --> Xerox --> Next. Then, right-click on the scanner and choose Properties --> Xerox Settings --> Add and then enter the IP address of the scanner. After scanning, double-click on the scanner, and WIA should reveal any scanned documents.--Best Dog Ever (talk) 08:24, 4 September 2010 (UTC)

Thanks, I'll try that. How can I verify whether the Xerox machin supports WIA? And will I need to install the TWAIN scan driver, or does WIA replace that functionality? Astronaut (talk) 08:52, 4 September 2010 (UTC)

Not a problem. WIA is a replacement for TWAIN. TWAIN is more full-featured, but always requires the installation of software from the manufacturer to function. TWAIN is also more tempermental. So, I always use WIA, simply because it's easier to setup. By the way, if the generic Xerox driver mentioned above doesn't work, click the "Have disk" button instead of "Next" and then point it to drivers on any disks that came with the scanner.--Best Dog Ever (talk) 09:04, 4 September 2010 (UTC)

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Wikipedia:Reference desk/Computing

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Contents

August 30

Add-ons

Hebrew font identification

VB.net

Compare code

High x16 PCIe 2.0 Slot-Count Barebone System

country ip masking

usb peripheral switch

Arcade Fire's Wilderness Downtown

Hard Drive

August 31

CD ripping -- byte perfect?

Opening image in new tab in same window in Internet Explorer by middle mouse

Motherboard: The new 'chairman'?

Preventing Windows Mail from marking email as phishing

Problem on saving DDS images with alpha

Must I retain Acrobat update files?

Error message on XBox

spam filter "throwing out" political messages

Processing-Core Price Disparity

Google Mail

SSD Roadmap

Buying a kindle edition book from amazon

September 2

Compiler Writing: NOT Parser Generators!

Backing-up to a NAS drive over the Internet?

This Type of Image

Difference between SIMD and Vector Processors

Conventional Explosives Simulation Software

Mini-flash cookie app

broadband numbers

Javascript wait

NP theory

Typing credit card details into SLL-enabled CGI proxies

Compressing

Domain Names

e-mail account hijacked

September 3

Idiotic and Useless Emails

data corruption

Parchive

Webpage to PDF

a/b drives

Javascript time

Cell Phone and Lap top

Methods for multiple classes

Terminal window of safari

September 4

Recovery of Deleted File on SD Card

What is the cellular 3G base station price range?

Scanning over the network

Views

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