Wikipedia:Reference desk/Archives/Computing/2013 November 26

= November 26 =

Power Supply Efficiency confusion
If a PSU is rated at 500 watts and has 80% efficiency, does that mean that (a) the PSU will actually pull 500 watts from the mains, and output 400 watts to the computer, or does it mean (b) that the PSU actually outputs 500 watts to the computer, and pulls 625 watts from the wall? 08:20, 26 November 2013 (UTC) — Preceding unsigned comment added by 119.56.118.12 (talk)
 * It's usually the second case, but you can confirm it by looking at the more detailed numbers on the label. It should tell how much current you can draw from each of the different lines. From there a little math (that they often do for you on the label) tells you how many Watts total are making it out to those lines. There should also be a number (probably a bit high to be safe) for how much it draws from the wall. K ati e R  (talk) 13:12, 26 November 2013 (UTC)
 * Note that most decent PSUs should not have a single efficiency rating as the efficiency will depend on the output power which in any modern computer will vary a lot depending on load. See for example the 80 Plus certification standard which specifies different minimum efficiencies at different output levels. And as Katie Ryan A said, a 500W PSU would normally imply that's the maximum power that can be supplied (although as has also been said each line will also have a limit), but you should check out the label, and for a crappy PSU which only specifies 80% efficiency I wouldn't trust the limits on the label anyway. (Actually I probably wouldn't trust such a PSU point blank.) Nil Einne (talk) 19:29, 26 November 2013 (UTC)

Screen resolution alternates when I reboot
When I reboot my Windows 7 64-bit PC, it alternates between starting up at two different resolutions. I think it's every other time. And when I go to change the resolution from the smaller one, I find that is the max res for that session. So, I reboot, and it fires up at the large res, and everything is fine, until the next time I reboot. This behavior started when my LCD monitor died and I hooked up an old, smaller, CRT monitor. So, I'd guess it sometimes loads the driver it thinks is good for the CRT, which gives me the small res, and sometimes loads the driver for the LCD monitor that died, which actually works great on the CRT, and gives me the higher res.

So, short of always rebooting twice or getting used to the small res, what can I do ? StuRat (talk) 04:29, 26 November 2013 (UTC)


 * Monitors communicate their available modes to the graphics card via a protocol called Display Data Channel, and consequently don't have drivers. I'm inclined to think that the graphics card must be malfunctioning (did the card kill the LCD by failing to respect its capabilities?), or possibly it is the aged monitor that is to blame and you in fact have two dead monitors. You have the correct drivers for the card installed, right? Card Zero  (talk) 10:05, 26 November 2013 (UTC)


 * I assume so, since it worked fine for over a year on the old monitor. I've also tested the broken monitor on another PC, and it doesn't work there, either. StuRat (talk) 09:17, 27 November 2013 (UTC)

YouTube + flash game problems.
I sometimes get this when trying to play a YouTube video in Firefox 26.0a1:

An ActionScript error has occurred: Error #2044: Unhandled securityError:. text=Error #2048: Security sandbox violation: http://s.ytimg.com/yts/swfbin/player-vfle5oFqK/watch_as3.swf cannot load data from http://r4---sn-xoxgbphpqu-3g2e.c.youtube.com/videoplayback?algorithm=throttle-factor&burst=40&clen=912697&cp=U0hXR1ZRUl9FT0NON19OS1ZIOlJEX2Fzc0VmQ1da&cpn=uSzBJrlGFyY0_Spe&dur=57.399&expire=1382664705&factor=1.25&fexp=916912%2C930103%2C932250%2C921087%2C916625%2C924616%2C924610%2C907231&gir=yes&id=9fb598b9f7d0a38a&ip=78.156.109.166&ipbits=8&itag=140&key=yt5&lmt=1382561812255366&ms=au&mt=1382641665&mv=m&signature=B481E13C2A9C3002D00882E823572CC4254149B5.F295E8E7DE6C07FF9E2075836C98365E99B7BCE7&source=youtube&sparams=algorithm%2Cburst%2Cclen%2Ccp%2Cdur%2Cfactor%2Cgir%2Cid%2Cip%2Cipbits%2Citag%2Clmt%2Csource%2Cupn%2Cexpire&sver=3&upn=aZS1EOw7Ov4&range=0-6950. Error #2044: Unhandled securityError:. text=Error #2048: Security sandbox violation: http://s.ytimg.com/yts/swfbin/player-vfle5oFqK/watch_as3.swf cannot load data from http://r4---sn-xoxgbphpqu-3g2e.c.youtube.com/videoplayback?algorithm=throttle-factor&burst=40&clen=1544046&cp=U0hXR1ZRUl9FT0NON19OS1ZIOlJEX2Fzc0VmQ1da&cpn=uSzBJrlGFyY0_Spe&dur=57.291&expire=1382664705&factor=1.25&fexp=916912%2C930103%2C932250%2C921087%2C916625%2C924616%2C924610%2C907231&gir=yes&id=9fb598b9f7d0a38a&ip=78.156.109.166&ipbits=8&itag=133&key=yt5&lmt=1382561820960995&ms=au&mt=1382641665&mv=m&signature=D96EA73DA90ECDFACE8592DEB735FC867D251C44.9C4ECFAF3E8C8ED56809EE80F80D421553367C6D&source=youtube&sparams=algorithm%2Cburst%2Cclen%2Ccp%2Cdur%2Cfactor%2Cgir%2Cid%2Cip%2Cipbits%2Citag%2Clmt%2Csource%2Cupn%2Cexpire&sver=3&upn=aZS1EOw7Ov4&range=0-8470. at com.google.youtube.players::TagStreamPlayer/createAppendBytesNetStream at com.google.youtube.players::TagStreamPlayer/getNewNetStream at com.google.youtube.players::HTTPVideoPlayer/connectStream at com.google.youtube.players::HTTPVideoPlayer/onNetStatus at com.google.youtube.players::TagStreamPlayer/onNetStatus at flash.net::NetConnection/connect at com.google.youtube.players::HTTPVideoPlayer/resetStream at com.google.youtube.players::HTTPVideoPlayer/initiatePlayback at com.google.youtube.players::TagStreamPlayer/initiatePlayback at com.google.youtube.players::BasePlayerState/play at com.google.youtube.players::BaseVideoPlayer/play at com.google.youtube.application::VideoApplication/playVideo at com.google.youtube.application::VideoApplication/startApplication at com.google.youtube.application::WatchPageVideoApplication/startApplication at com.google.youtube.application::VideoApplication/onInited at com.google.youtube.application::Application/initData at com.google.youtube.application::VideoApplication/initData at com.google.youtube.application::WatchPageVideoApplication/initData at Function/http://adobe.com/AS3/2006/builtin::apply at com.google.youtube.application::VideoApplication/guardedCall at com.google.youtube.application::Application/init at com.google.youtube.application::VideoApplication/init at com.google.youtube.application::WatchPageVideoApplication/init at com.google.youtube.application::VideoApplication/onLoaderInfoInit

And sometimes I get this: Warning: Unresponsive script. The flash player plugin has stopped responding. You can see if it completes or stop the script now. Also why do YouTube videos work for me in Internet Explorer 11 but not in Firefox 26.0a1? In Firefox, it says "An error has occurred. Please try again later. Learn more" in the place where the video is supposed to be. And get this when loading Cursed Treasure 2: An ActionScript error has occurred: Error #2044: Unhandled IOErrorEvent:. text=Error #2124: Loaded file is an unknown type. — Preceding unsigned comment added by 78.156.109.166 (talk) 09:44, 26 November 2013 (UTC)


 * I have reformatted the error message so it doesn't disrupt the rest of the page layout. Nimur (talk) 15:23, 26 November 2013 (UTC)


 * Your first error occurs because of a poorly-thought-out web design on YouTube: a server that delivers your video needs to load a file from a different server. One file is hosted on youtube.com, and one is hosted on the YouTube content delivery network aliased as "ytimg.com" - which sets off your flash plugin's security alarm, because it looks like a cross site scripting attack (attempting to load resources from a separate top level domain).  There is nothing to suggest it's a real malware attack; it's just poorly architected server aliasing, and has a symptom that looks fishy to Firefox's sandbox.
 * Your second error can occur because the Flash plug-in is loading or running too slowly. Firefox assumes the plug-in has crashed, and asks if you want to force-quit it.  Sometimes, Flash plugin actually has crashed; and sometimes the game or video you're loading is just poorly implemented and runs very slowly; so Firefox lets you decide whether to wait or force-terminate.  Nimur (talk) 15:53, 26 November 2013 (UTC)
 * I'd like solutions. 78.156.109.166 (talk) 10:06, 28 November 2013 (UTC)
 * Maybe the solution got lost in technobabble, but to summarize, there is almost nothing you can do as an end-user to fix these issues. These bugs need to be fixed by the server administrators and programmers who created the software.  You can send bug-reports to the authors of those softwares, in the hopes that it will expedite a fix.
 * You can work around the plug-in sandboxing issue on YouTube by disabling your Flash plug-in, and streaming video directly to your browser. On YouTube, this is branded as switching to "html5 video."
 * The other issue you described in the game is a totally unrelated problem. You can send a bug report to the software author, but it looks like his game was created as "work for hire," so it might be complicated to get a fix pushed to the game's publisher.  Nimur (talk) 10:28, 28 November 2013 (UTC)
 * I can't watch YouTube videos in Internet Explorer also, because it redirects to another page. And I have to press Esc many times to prevent that, but still, most videos stop after a few seconds (after the ad), what can I do? How does one stream videos directly? Sorry, I don't have access to Google, and even if, I wouldn't be able to focus on it/understand it. 78.156.109.166 (talk) 19:06, 28 November 2013 (UTC)

not understanding b trees
hello, can someone help me out with this? i have to create a b tree with order 3 with the following values: 12, 24, 7, 4, 30, 13, 19, 27, 8, 10, 2, 18, 21, 14. when creating it, i run into trouble adding 13. this is what i sketch 12 | 13        /      \      4 | 7      24 | 30 however, this is incorrect. the correct method is: 12 | 24        /   \    \      4 | 7   13   30

why is my method wrong? and what exactly does order 3 mean? because at the end of the b tree, only the second row actually has 3 things in it. this is the final result: 12          /         \          7           18 | 24        /  \        /      /     \    2 | 4  8 | 10 13 | 14 19 | 21   27 | 30 205.211.50.163 (talk) 20:38, 26 November 2013 (UTC)


 * What is making you decide to move the 24 when you insert 13? In an order N tree, you can have anywhere between N/2 and N children per node. In your final example, all non-leaf nodes have 2 or 3 children, so they are following the N/2 to N rule. Our B-Tree article has a good example work-through of the insertion algorithm if you haven't already read it. K ati e R  (talk) 20:43, 26 November 2013 (UTC)
 * are you talking about what i did or the solution? because in my mind i see nothing wrong with having 12 and 13 as the root, but the solution provided by my professor has 24 and 12 as the root with 13 put below. anyway ill read the article more thoroughly, i was given basically three powerpoint slides on the formula used for b trees and thats all. thanks 205.211.50.163 (talk) 20:48, 26 November 2013 (UTC)
 * I was asking about your workthrough of the first few elements. If you follow the algorithm described in the page, you should see 24 at the root at that stage, just like in the correct solution you posted. Let us know if you're still having trouble after reading through the article, in particular the part with the insertion algorithm. I probably won't be back online until Monday, so this post will likely be archived by then, but someone else may be able to help. K ati e R  (talk) 16:19, 27 November 2013 (UTC)
 * I would like to add that your example is a valid b-tree, that is it follows all of the rules for how many elements are in the nodes and how they are arranged. The problem is that the standard b-tree algorithm would not have created that particular layout given the elements in the order you listed. K ati e R  (talk) 16:26, 27 November 2013 (UTC)


 * The first image is wrong:

12 | 13        /      \      4 | 7      24 | 30
 * If a root node contains 2 keys (12 and 13) then it should have 3 children nodes – one for keys less than 12, one for those between 12 and 13, and the last one for those greater than 13.
 * After adding 12, 24, 7, 4, 30 into an empty tree you should get:

12         /    \     4 | 7      24 | 30
 * Then 13 goes right from the root node and falls into the (24, 30) page. The page then overflows and gets splitted into single–key pages (13) and (30) while the middle item (24) is returned back to the root page. Finally

12 | 24        /   \   \    4 | 7    13   30
 * Check again how you handle splitting the node when is gets overfilled. --CiaPan (talk) 07:28, 3 December 2013 (UTC)


 * Good point - I missed that when I said that it looked valid. I think our OP is long gone anyways... K ati e R  (talk) 17:46, 3 December 2013 (UTC)

Bandwidth shaping
A few weeks ago I asked a question here about the possibility that my ISP is throttling my file transfer. I use a program called CrashPlan to back files on my PC to a hard drive I put into my mother's PC. When I reported the problem previously, I said that the usual upload rate was ~800 KBps when I actually meant 800 Kbps and this was determined to be normal because it is eight times the speed I actually achieve. I've seen it exceed 4 Mbps but it normally doesn't reach that for very long. So is my ISP reducing my bandwidth, perhaps because they think I'm illegally file-sharing? If I leave my computer and my mother's computer on, it will take 50 days to complete at the current transfer rate (430 GB to transfer)! — Preceding unsigned comment added by 78.148.107.181 (talk) 21:05, 26 November 2013 (UTC)


 * What is your ISP and your mother's ISP? Some ISPs simply throttle every TCP connection after the first few megabytes (my Google-fu is failing me, so this is from memory). You might annoy the ISP in any case if you transfer 430 GB of data, even if it takes 50 days. Theoretically the information about throttling and monthly maximums should be published in the ISP's terms of service.
 * If your computer and your mother's computer are in the same house, the transfer should happen over the local network at a much higher speed without the ISP being involved at all. Otherwise, it would make sense to temporarily attach the drive to your computer for the initial backup. If CrashPlan doesn't support either of those things, you might want to consider different backup software. -- BenRG (talk) 22:07, 26 November 2013 (UTC)


 * If you visit her frequently, borrow an external hard drive and take that over. --Aspro (talk) 01:15, 27 November 2013 (UTC)