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• Partition of tables in MySQL

  - by Joel

  Hello, I have read that in a case where a table has many columns, but most of the time only one of them is used (say a title column in a forum post), a way to increase performance would be a partition to two tables, where one will contain only the title and the other one will contain the other columns (such as the forum post body). However, in case I use select ForumTitle from Forum; won't that be good enough to prevent the load of all columns (such as the forum post's body) to the memory, and eliminate the need of partition? Thanks, Joel

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• Video with QML Video plays choppy on Mac OS X

  - by avida

  I’m trying to create simple video player with QML. I have QtSdk installed and QtMobility compiled and installed from source. Then I put this simple video playing code to main qml file: import QtQuick 1.0 import QtMultimediaKit 1.1 Item{ width: 400; height: 300 Video { id: video source: "d:/Projects/Serenity - HD DVD Trailer.mp4" anchors.fill: parent MouseArea { anchors.fill: parent onClicked: { video.play() } } } } After compiling and running application, video plays choppy and on exiting application it puts this in log: 2011-06-07 11:13:44.055 video-player[323:903] *** __NSAutoreleaseNoPool(): Object 0x10225ea60 of class NSCFNumber autoreleased with no pool in place - just leaking 2011-06-07 11:13:45.007 video-player[323:903] *** __NSAutoreleaseNoPool(): Object 0x10264f030 of class __NSCFDate autoreleased with no pool in place - just leaking 2011-06-07 11:13:45.007 video-player[323:903] *** __NSAutoreleaseNoPool(): Object 0x11a409000 of class NSCFTimer autoreleased with no pool in place - just leaking 2011-06-07 11:13:45.008 video-player[323:903] *** __NSAutoreleaseNoPool(): Object 0x11a43e550 of class NSCFArray autoreleased with no pool in place - just leaking 2011-06-07 11:13:45.008 video-player[323:903] *** __NSAutoreleaseNoPool(): Object 0x11a462560 of class __NSFastEnumerationEnumerator autoreleased with no pool in place - just leaking If any way to make it playing smoothly and to prevent memory?

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• how to debug SIGSEGV in jvm GCTaskThread

  - by ekeren

  Hi, My application is experiencing cashes in production. The crash dump indicates a SIGSEGV has occurred in GCTaskThread It uses JNI, so there might be some source for memory corruption, although I can't be sure. How can I debug this problem - I though of doing -XX:OnError... but i am not sure what will help me debug this. Also, can some of you give a concrete example on how JNI code can crash GC with SIGSEGV EDIT: OS:SUSE Linux Enterprise Server 10 (x86_64) vm_info: Java HotSpot(TM) 64-Bit Server VM (11.0-b15) for linux-amd64 JRE (1.6.0_10-b33), built on Sep 26 2008 01:10:29 by "java_re" with gcc 3.2.2 (SuSE Linux)

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• Detecting that the stack is full in C/C++

  - by Martin Kristiansen

  When writing C++ code I've learned that using the stack to store memory is a good idea. But recently I ran into a problem: I had an experiment that had code that looked like this: void fun(unsigned int N) { float data_1[N*N]; float data_2[N*N]; /* Do magic */ } The code exploted with a seqmentation fault at random, and I had no idea why. It turned out that problem was that I was trying to store things that were to big on my stack, is there a way of detecting this? Or at least detecting that it has gone wrong?

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• immutable strings vs std::string

  - by Caspin

  I've recent been reading about immutable strings, here and here as well some stuff about why D chose immutable strings. There seem to be many advantages. trivially thread safe more secure more memory efficient in most use cases. cheap substrings (tokenizing and slicing) Not to mention most new languages have immutable strings, D2.0, Java, C#, Python, Ruby, etc. Would C++ benefit from immutable strings? Is it possible to implement an immutable string class in c++ (or c++0x) that would have all of these advantages?

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• MySqlDataAdapter or MySqlDataReader for bulk transfer?

  - by Jeff Meatball Yang

  I'm using the MySql connector for .NET to copy data from MySql servers to SQL Server 2008. Has anyone experienced better performance using one of the following, versus the other? DataAdapter and calling Fill to a DataTable in chunks of 500 DataReader.Read to a DataTable in a loop of 500 I am then using SqlBulkCopy to load the 500 DataTable rows, then continue looping until the MySql record set is completely transferred. I am primarily concerned with using a reasonable amount of memory and completing in a short amount of time. Any help would be appreciated!

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• Would watching a file for changes or redundantly querying that file be more efficient?

  - by badpanda

  I am wondering whether watching a file/directory for changes using the FileSystemWatcher class is extremely memory intensive. I am developing a desktop application in C# that will be running behind the scenes continuously on low-performance computers, and I need some way of checking to see if various files have changed. I can think of a few solutions: Watch the directories using FileSystemWatcher. Run a timed thread on an interval that goes through and manually checks this. Check manually every time the actionhandler thread runs (the program will occasionally do something, on an action). Any suggestions? Thanks! badPanda

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• Declaring local variables in assembly

  - by dcmoebius

  Is it possible to allocate locally-scoped memory in assembly? For example, consider the following (completely contrived) situation: I have two macros, one of which is dependent on the other. The first is: minimum MACRO dest, num1, num2 ; Finds the minimum of two unsigned numbers, stores the result in dest And the second is: tripMin MACRO dest, num1, num2, num3 ; Finds the minimum of three unsigned numbers, stores the result in dest minimum firstMin, num1, num2 minimum secondMin, num2, num3 minimum dest, firstMin, secondMin (I know that this isn't a realistic example for a variety of reasons, but bear with me.) Assuming that all the registers are otherwise occupied, is there any way to declare firstMin and secondMin locally within the macro? Or am I just better off freeing a register by pushing its value onto the stack and popping it back when I'm done?

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• Disk-based caching of dynamic images in IIS 7

  - by Daniel Schierbeck

  I'm writing an image server which needs to handle a relatively large number of concurrent requests (~5,000). The images being served are dynamically scaled down and cropped based on per-image specifications, which are queried from a database. The number of images is rather large, so an in-memory cache isn't viable (thrashing would most definitely occur). I'm using native caching in IIS 7 to avoid hitting the ASP.NET app which generates the images on-the-fly. I've looked around, but I couldn't find a simple way to configure IIS to store the cache on-disk -- is there such an option, or would I need to roll my own? I'd rather avoid placing the generated images in a public folder, so they can be served statically, since I would prefer to invalidate the cache entries using a query parameter (last-edit time from the database,) which doesn't seem possible to reconcile with static caching. I would love to get some feedback on this!

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• 0xDEADBEEF equivalent for 64-bit development?

  - by Peter Mortensen

  For C++ development for 32-bit systems (be it Linux, Mac OS or Windows, PowerPC or x86) I have initialised pointers that would otherwise be undefined (e.g. they can not immediately get a proper value) like so: int *pInt = reinterpret_cast<int *>(0xDEADBEEF); (To save typing and being DRY the right-hand side would normally be in a constant, e.g. BAD_PTR.) If pInt is dereferenced before it gets a proper value then it will crash immediately on most systems (instead of crashing much later when some memory is overwritten or going into a very long loop). Of course the behavior is dependent on the underlying hardware (getting a 4 byte integer from the odd address 0xDEADBEEF from a user process may be perfectly valid), but the crashing has been 100% reliable for all the systems I have developed for so far (Mac OS 68xxx, Mac OS PowerPC, Linux Redhat Pentium, Windows GUI Pentium, Windows console Pentium). For instance on PowerPC it is illegal (bus fault) to fetch a 4 byte integer from an odd address. What is a good value for this on 64-bit systems?

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• How do I send a PDF in a MemoryStream to the printer in .Net?

  - by Ryan ONeill

  I have a PDF created in memory using iTextSharp and contained in a MemoryStream. I now need to translate that MemoryStream PDF into something the printer understands. I've used Report Server in the past to render the pages to the printer format but I cant use it for this project. Is there a native .Net way of doing this? For example, GhostScript would be OK if it was a .Net assembly but I don't want to bundle any non .Net stuff along with my installer. The PrintDocument class in .Net is great for sending content to the printer but I still need to translate it from a PDF stream into GDI at the page level. Any good hints? Thanks in advance Ryan

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• Limiting the size of the managed heap in a C# application

  - by Assaf Lavie

  Can I configure my C# application to limit its memory consumption to, say, 200MB? IOW, I don't want to wait for the automatic GC (which seems to allow the heap to grow much more than actually needed by this application). I know that in Java there's a command line switch you can pass to the JVM that achieves this.. is there an equivalent in C#? p.s. I know that I can invoke the GC from code, but that's something I would rather not have to do periodically. I'd rather set it once upon startup somehow and forget it.

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• render HTML (convert to bitmap)

  - by MK

  Can somebody recommend the best (and preferably portable) way to render HTML documents onto a bitmap? As far as I understand my main 2 options are WebKit and Gecko, but I wasn't able to find a good starting point on how to do it. When I last tried doing this 5 years ago, I ended up using Gecko to send the document to a printer, which is not really what I need. I need rendering to a in-memory bitmap. To clarify: server side, no Java, no .NET, batch processing, performance, not interactive, no Javascript.

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• See if any application has a DLL from the GAC loaded

  - by rwmnau

  I'm trying to deploy new copies of my DLL to the GAC on remote servers, but I need to identify if any processes currently running have a loaded copy of the DLL I'm replacing - I'd like to restart them, or at least tell the user. For example, Biztalk seems to load the DLLs it needs the first time they're used, and then replacing them keeps the old copy in memory until the Host Instances are restarted - something I could easily do as part of my deployment. Is there a way to tell using .NET which processes have loaded a particular DLL from the GAC? UPDATE: Some further investigation shows that both Process Explorer has this functionality, and another Sysinternals tool, ListDLL, does exactly what I want to be able to do. I'd like to know how they do it, since I'd love to replicate this functionality in my application without having to include and screen-scrape ListDLL (if that's even allowed inside the license).

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• When getting substring in .Net, does the new string reference the same original string data or does

  - by Elan

  Assuming I have the following strings: string str1 = "Hello World!"; string str2 = str1.SubString(6, 5); // "World" I am hoping that in the above example str2 does not copy "World", but simply ends up being a new string that points to the same memory space only that it starts with an offset of 6 and a length of 5. In actuality I am dealing with some potentially very long strings and am interested in how this works behind the scenes for performance reasons. I am not familiar enaugh with IL to look into this.

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• Why isn't Passenger respecting my custom log format?

  - by Millisami

  I need to change the log format of my rails app. I put this file in lib directory and required it in development.rb env file. require 'hodel_3000_compliant_logger' config.logger = Hodel3000CompliantLogger.new(config.log_path) and I should get the output of the development.log file as follows: Jun 28 03:05:13 millisami-notebook rails[18243]: Memory usage: 86888 | PID: 18243 I get this exact log when I start my app with script/server (Mongrel). But when I run the app via Passenger, the format being logged is Rails' default. Why doesn't Passenger write to the log file like Mongrel does?

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• Slow page unload in IE

  - by ForYourOwnGood

  I am developing a site which creates many table rows dynamically. The total amount of rows right now is 187. Everything works fine when creating the rows, but in IE when I leave the page, there is a large amount of lag. I do not know if this is some how related to the heavy DOM manipulation I am doing in the page? I do not create any function closures when building the dynamic content's event handlers so I do not believe this problem is related to memory leaks. Any insight is much appreciated.

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• plist vs static array

  - by morticae

  Generally, I use static arrays and dictionaries for containing lookup tables in my classes. However, with the number of classes creeping quickly into the hundreds, I'm hesitant to continue using this pattern. Even if these static collections are initialized lazily, I've essentially got a bounded memory leak going on as someone uses my app. Most of these are arrays of strings so I can convert strings into NSInteger constants that can be used with switch statements, etc. I could just recreate the array/dictionary on every call, but many of these functions are used heavily and/or in tight loops. So I'm trying to come up with a pattern that is both performant and not persistent. If I store the information in a plist, does the iphoneOS do anything intelligent about caching those when loaded? Do you have another method that might be related?

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• How to stop a curl while requesting or stop the running php script?

  - by Chris

  I using url to request remote urls that sometimes may very slow or just down. In this case, my php scripts still waiting for the response, it makes apache has to many requests stay in memory and then overload. I need a way to stop curl requesting or stop running php script when specified time passed. I'd tried declare(), it makes no sense for curl. Can someone know how to solve it? BTW: what is the effect of CURLOPT_CONNECTTIMEOUT and CURLOPT_TIMEOUT? They don't work like what I think.

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• Beginner question: What is binding?

  - by JDelage

  Hi, I was trying to understand the difference between early and late binding, and in the process realized that the concept of binding is nebulous to me. I think I understand that it relates to the way data-as-a-word-of-memory is linked to type-as-a-set-of-language-features but I am not sure those are the right concepts. Also, how does understanding this deeply help people become better programmers? Please note: This question is not "what is late v. early binding" or "what are the trade-offs between the 2". Those already exist here. Thanks, JDelage

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• Whats the problem with int *p; *p=23;

  - by piemesons

  Yesterday in my interview I was asked this question. (At that time I was highly pressurized by so many abrupt questions). int *p; *p=23; printf('%d',*p); Is there any problem with this code? I explained him that you are trying to assign value to a pointer to whom memory is not allocated. But the way he reacted, it was like I am wrong. Although I got the job but after that he said Mohit think about this question again. I don't know what he was trying to say. Please let me know is there any problem in my answer?

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• Optimize code perfromance when odd/even threads are doing different things in CUDA

  - by Ashraf

  Hi all! I have two large vectors, I am trying to do some sort of element multiplication, where an even-numbered element in the first vector is multiplied by the next odd-numbered element in the second vector .... and where the odd-numbered element in the first vector is multiplied by the preceding even-numbered element in the second vector Ex. vector 1 is V1(1) V1(2) V1(3) V1(4) vector 2 is V2(1) V2(2) V2(3) V2(4) V1(1) * V2(2) V1(3) * V2(4) V1(2) * V2(1) V1(4) * V2(3) I have written a Cuda code to do this: (Pds has the elements of the first vector in shared memory, Nds the second Vector) //instead of using %2 .. i check for the first bit to decide if number is odd/even -- faster if ((tx & 0x0001) == 0x0000) Nds[tx+1] = Pds[tx] * Nds[tx+1]; else Nds[tx-1] = Pds[tx] * Nds[tx-1]; __syncthreads(); Is there anyway to further accelerate this code or avoid divergence .. Thanks

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• Performance monitor shows 4294967293 sessions active

  - by TGnat

  I have an ASP.Net 3.5 website running in IIS 6 on Windows Server 2003 R2. It is a relatively small internal application that probably serves less than ten users at any given time. The server has 4 Gig of memory and shows that 3+ Gig is available while the site is active. Just minutes after restarting the web application Performance monitor shows that there is a whopping 4,294,967,293 sessions active! I am fairly certain that this number is incorrect; at the time this reading there were only 100 requests to the website. Has anyone else experienced this kind odd behavior from perf mon? Any ideas on how to get an accurate reading? UPDATE: After running for about an hour the number of active sessions has dropped by 4. So it does seem to be responding to sessions timing out.

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• CPU and Data alignment

  - by MS

  Dear All, Pardon me if you feel this has been answered numerous times, but I need answers to the following queries! Why data has to be aligned (on 4 byte/ 8 byte/ 2 byte boundaries)? Here my doubt is when the CPU has address lines Ax Ax-1 Ax-2 ... A2 A1 A0 then it is quite possible to address the memory locations sequentially. So why there is the need to align the data at specific boundaries? How to find the alignment requirements when I am compiling my code and generating the executatble? If for e.g the data alignment is 4 byte boundary, does that mean each consecutive byte is located at modulo 4 offsets? My doubt is if data is 4 byte aligned does that mean that if a byte is at 1004 then the next byte is at 1008 (or at 1005)? Your thoughts are much welcome. Thanks in advance! /MS

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• iPad crashes that aren't happening on iPhone or iPod Touch

  - by alyoshak

  Has anyone had difficulty getting what has otherwise been a solid iPhone app working on the iPad? I was under the impression that iPhone apps would run without problems on the iPad. We are are experiencing crashes (not intermittent - same place, at same time) that we've never gotten on the iPhone or iPod Touch. I have become suspicious that the crashes are memory-management related, but even if so, why only on the iPad? 2010-05-17 10:19:06.474 ASSIST[82:207] *** Terminating app due to uncaught exception 'NSUnknownKeyException', reason: '[<UISectionRowData 0x6041480> valueForUndefinedKey:]: this class is not key value coding-compliant for the key deliveryDate.' 2010-05-17 10:19:06.481 ASSIST[82:207] Stack: ( 852041337, 861292157, 852040861, 850755255, 850750995, 850758945, 81279, 123007, 126693, 149141, 851599725, 827486573, 827486477, 827486431, 827485745, 827487359, 827454123, 851903137, 851590065, 851588321, 819339483, 819339655, 827151561, 827144691, 9461, 9324 ) terminate called after throwing an instance of 'NSException' Program received signal: “SIGABRT”.

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