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• western digital caviar black. EXT4-fs error

  - by azat

  Recently I update my HDD on desktop machine, and bought WD Caviar Black. But after I format & copy information to it (using dd), and fix partitions size: I have next errors in kern.log: Aug 27 16:04:35 home-spb kernel: [148265.326264] EXT4-fs error (device sdc2): ext4_mb_generate_buddy:739: group 9054, 32254 clusters in bitmap, 32258 in gd Aug 27 16:07:11 home-spb kernel: [148421.493483] EXT4-fs error (device sdc2): ext4_mb_generate_buddy:739: group 9045, 32254 clusters in bitmap, 32258 in gd Aug 27 16:09:17 home-spb kernel: [148546.481693] EXT4-fs error (device sdc2): ext4_mb_generate_buddy:739: group 10299, 32254 clusters in bitmap, 32258 in gd Aug 27 16:09:17 home-spb kernel: [148546.487147] JBD2: Spotted dirty metadata buffer (dev = sdc2, blocknr = 0). There's a risk of filesystem corruption in case of system crash. Aug 27 16:09:42 home-spb kernel: [148572.258711] EXT4-fs error (device sdc2): ext4_mb_generate_buddy:739: group 4345, 32254 clusters in bitmap, 32258 in gd Aug 27 16:09:42 home-spb kernel: [148572.277591] JBD2: Spotted dirty metadata buffer (dev = sdc2, blocknr = 0). There's a risk of filesystem corruption in case of system crash. Aug 27 16:09:42 home-spb kernel: [148572.278202] EXT4-fs error (device sdc2): ext4_mb_generate_buddy:739: group 4344, 32254 clusters in bitmap, 32258 in gd Aug 27 16:09:42 home-spb kernel: [148572.284760] JBD2: Spotted dirty metadata buffer (dev = sdc2, blocknr = 0). There's a risk of filesystem corruption in case of system crash. Aug 27 16:09:42 home-spb kernel: [148572.291983] EXT4-fs error (device sdc2): ext4_mb_generate_buddy:739: group 9051, 32254 clusters in bitmap, 32258 in gd Aug 27 16:09:42 home-spb kernel: [148572.297495] JBD2: Spotted dirty metadata buffer (dev = sdc2, blocknr = 0). There's a risk of filesystem corruption in case of system crash. Aug 27 16:09:42 home-spb kernel: [148572.297916] EXT4-fs error (device sdc2): ext4_mb_generate_buddy:739: group 9050, 32254 clusters in bitmap, 32258 in gd Aug 27 16:09:42 home-spb kernel: [148572.297940] JBD2: Spotted dirty metadata buffer (dev = sdc2, blocknr = 0). There's a risk of filesystem corruption in case of system crash. Aug 27 16:09:42 home-spb kernel: [148572.303213] EXT4-fs error (device sdc2): ext4_mb_generate_buddy:739: group 4425, 32254 clusters in bitmap, 32258 in gd Aug 27 16:09:42 home-spb kernel: [148572.312127] JBD2: Spotted dirty metadata buffer (dev = sdc2, blocknr = 0). There's a risk of filesystem corruption in case of system crash. Aug 27 16:09:42 home-spb kernel: [148572.312487] EXT4-fs error (device sdc2): ext4_mb_generate_buddy:739: group 4424, 32254 clusters in bitmap, 32258 in gd Aug 27 16:09:42 home-spb kernel: [148572.317858] JBD2: Spotted dirty metadata buffer (dev = sdc2, blocknr = 0). There's a risk of filesystem corruption in case of system crash. Aug 27 16:09:42 home-spb kernel: [148572.322231] EXT4-fs error (device sdc2): ext4_mb_generate_buddy:739: group 4336, 32254 clusters in bitmap, 32258 in gd Aug 27 16:09:42 home-spb kernel: [148572.326250] JBD2: Spotted dirty metadata buffer (dev = sdc2, blocknr = 0). There's a risk of filesystem corruption in case of system crash. Aug 27 16:09:42 home-spb kernel: [148572.326599] EXT4-fs error (device sdc2): ext4_mb_generate_buddy:739: group 4335, 32254 clusters in bitmap, 32258 in gd Aug 27 16:09:42 home-spb kernel: [148572.332397] JBD2: Spotted dirty metadata buffer (dev = sdc2, blocknr = 0). There's a risk of filesystem corruption in case of system crash. Aug 27 16:09:42 home-spb kernel: [148572.341957] EXT4-fs error (device sdc2): ext4_mb_generate_buddy:739: group 5764, 32254 clusters in bitmap, 32258 in gd Aug 27 16:09:42 home-spb kernel: [148572.350709] JBD2: Spotted dirty metadata buffer (dev = sdc2, blocknr = 0). There's a risk of filesystem corruption in case of system crash. Aug 27 16:09:42 home-spb kernel: [148572.351127] EXT4-fs error (device sdc2): ext4_mb_generate_buddy:739: group 5763, 32254 clusters in bitmap, 32258 in gd Aug 27 16:09:42 home-spb kernel: [148572.355916] JBD2: Spotted dirty metadata buffer (dev = sdc2, blocknr = 0). There's a risk of filesystem corruption in case of system crash. Aug 27 16:09:43 home-spb kernel: [148572.401055] EXT4-fs error (device sdc2): ext4_mb_generate_buddy:739: group 10063, 32254 clusters in bitmap, 32258 in gd Aug 27 16:09:43 home-spb kernel: [148572.404357] JBD2: Spotted dirty metadata buffer (dev = sdc2, blocknr = 0). There's a risk of filesystem corruption in case of system crash. Aug 27 16:09:43 home-spb kernel: [148572.414699] EXT4-fs error (device sdc2): ext4_mb_generate_buddy:739: group 10073, 32254 clusters in bitmap, 32258 in gd Aug 27 16:09:43 home-spb kernel: [148572.420411] JBD2: Spotted dirty metadata buffer (dev = sdc2, blocknr = 0). There's a risk of filesystem corruption in case of system crash. Aug 27 16:09:43 home-spb kernel: [148572.493933] EXT4-fs error (device sdc2): ext4_mb_generate_buddy:739: group 9059, 32254 clusters in bitmap, 32258 in gd Aug 27 16:09:43 home-spb kernel: [148572.493956] JBD2: Spotted dirty metadata buffer (dev = sdc2, blocknr = 0). There's a risk of filesystem corruption in case of system crash. One time, machine rebooted (not manually), when I turn it on, it runs fsck on /dev/sdc2 and fix some errors and some files are missing on /dev/sdc2 I'v check /dev/sdc2 for badblocks, it doesn't have it ( using e2fsck -c /dev/sdc2 ) Here is the output of fsck http://pastebin.com/D5LmLVBY What else I can do to understand what's wrong here? BTW for /dev/sdc1 no message like that, in kern.log Linux version: 3.3.0 Distributive: Debian wheezy

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• adjacency list creation , out of Memory error

  - by p1

  Hello , I am trying to create an adjacency list to store a graph.The implementation works fine while storing 100,000 records. However,when I tried to store around 1million records I ran into OutofMemory Error : Exception in thread "main" java.lang.OutOfMemoryError: Java heap space at java.util.Arrays.copyOfRange(Arrays.java:3209) at java.lang.String.(String.java:215) at java.io.BufferedReader.readLine(BufferedReader.java:331) at java.io.BufferedReader.readLine(BufferedReader.java:362) at liarliar.main(liarliar.java:39) Following is my implementation HashMap<String,ArrayList<String>> adj = new HashMap<String,ArrayList<String>>(num); while ((str = in.readLine()) != null) { StringTokenizer Tok = new StringTokenizer(str); name = (String) Tok.nextElement(); cnt = Integer.valueOf(Tok.nextToken()); ArrayList<String> templist = new ArrayList<String>(cnt); while(cnt>0) { templist.add(in.readLine()); cnt--; } adj.put(name,templist); } //done creating a adjacency list I am wondering, if there is any better way to implement the adjacency list. Also, I know number of nodes right in the begining and , in the future I flatten the list as I visit nodes. Any suggestions ? Thanks

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• Please help us non-C++ developers understand what RAII is

  - by Charlie Flowers

  Another question I thought for sure would have been asked before, but I don't see it in the "Related Questions" list. Could you C++ developers please give us a good description of what RAII is, why it is important, and whether or not it might have any relevance to other languages? I do know a little bit. I believe it stands for "Resource Acquisition is Initialization". However, that name doesn't jive with my (possibly incorrect) understanding of what RAII is: I get the impression that RAII is a way of initializing objects on the stack such that, when those variables go out of scope, the destructors will automatically be called causing the resources to be cleaned up. So why isn't that called "using the stack to trigger cleanup" (UTSTTC:)? How do you get from there to "RAII"? And how can you make something on the stack that will cause the cleanup of something that lives on the heap? Also, are there cases where you can't use RAII? Do you ever find yourself wishing for garbage collection? At least a garbage collector you could use for some objects while letting others be managed? Thanks.

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• Weird call stack when application has frozen

  - by Harriv

  I apparently have an dead lock problem in one of my applications and started investigating EurekaLog stack traces. Here's one recent: Call Stack Information: -------------------------------------------------------------------------------------------------------------------------------------- |Address |Module |Unit |Class |Procedure/Method |Line | -------------------------------------------------------------------------------------------------------------------------------------- |*Exception Thread: ID=14208; Priority=0; Class=; [Main] | |------------------------------------------------------------------------------------------------------------------------------------| |7C82860C|ntdll.dll | | |KiFastSystemCall | | |7C827D27|ntdll.dll | | |ZwWaitForSingleObject | | |77E61C96|kernel32.dll | | |WaitForSingleObjectEx | | |77E61C88|kernel32.dll | | |WaitForSingleObject | | |77E61C7B|kernel32.dll | | |WaitForSingleObject | | |004151C4|MyApp.exe |sysutils.pas |TMultiReadExclusiveWriteSynchronizer|WaitForWriteSignal |16740[1] | |004151BC|MyApp.exe |sysutils.pas |TMultiReadExclusiveWriteSynchronizer|WaitForWriteSignal |16740[1] | |0041522C|MyApp.exe |sysutils.pas |TMultiReadExclusiveWriteSynchronizer|BeginWrite |16818[57] | |004323FB|MyApp.exe |Classes.pas |TDataModule |Create |11357[1] | |004323C0|MyApp.exe |Classes.pas |TDataModule |Create |11356[0] | |007D744D|MyApp.exe |uRORemoteDataModule.pas |TRORemoteDataModule |Create |163[1] | |007D7434|MyApp.exe |uRORemoteDataModule.pas |TRORemoteDataModule |Create |162[0] | |007DBFAB|MyApp.exe |Sentrol_Impl.pas | |Create_Sentrol |85[1] | |00646952|MyApp.exe |uROServer.pas |TROInvoker |CustomHandleMessage |726[11] | |00407BFA|MyApp.exe |system.pas |TInterfacedObject |_AddRef |17972[1] | |00404934|MyApp.exe |system.pas |TObject |GetInterface |9003[8] | |00407B1C|MyApp.exe |system.pas | |_IntfClear |17817[1] | |00404966|MyApp.exe |system.pas |TObject |GetInterface |9009[14] | |004048E8|MyApp.exe |system.pas |TObject |GetInterface |8995[0] | |00407BD7|MyApp.exe |system.pas |TInterfacedObject |QueryInterface |17964[1] | |77E61680|kernel32.dll | | |InterlockedDecrement | | |00407C10|MyApp.exe |system.pas |TInterfacedObject |_Release |17977[1] | |00407B2C|MyApp.exe |system.pas | |_IntfClear |17824[8] | |004067DF|MyApp.exe |system.pas | |_FinalizeArray |15233[100]| |00407B1C|MyApp.exe |system.pas | |_IntfClear |17817[1] | |00646577|MyApp.exe |uROServer.pas |TROClassFactoryList |FindClassFactoryByInterfaceName|619[17] | |77E6166C|kernel32.dll | | |InterlockedIncrement | | |00407BFA|MyApp.exe |system.pas |TInterfacedObject |_AddRef |17972[1] | |00646B72|MyApp.exe |uROServer.pas |TROInvoker |HandleMessage |758[1] | |006460C5|MyApp.exe |uROServer.pas | |MainProcessMessage |512[98] | |00645BAC|MyApp.exe |uROServer.pas | |MainProcessMessage |414[0] | |00647184|MyApp.exe |uROServer.pas |TROMessageDispatcher |ProcessMessage |929[2] | |00647130|MyApp.exe |uROServer.pas |TROMessageDispatcher |ProcessMessage |927[0] | |00647BCF|MyApp.exe |uROServer.pas |TROServer |IntDispatchMessage |1328[27] | |00647ABC|MyApp.exe |uROServer.pas |TROServer |IntDispatchMessage |1301[0] | |0064782F|MyApp.exe |uROServer.pas |TROServer |DispatchMessage |1170[11] | |006477B4|MyApp.exe |uROServer.pas |TROServer |DispatchMessage |1159[0] | |006477A9|MyApp.exe |uROServer.pas |TROServer |DispatchMessage |1152[1] | |0064779C|MyApp.exe |uROServer.pas |TROServer |DispatchMessage |1151[0] | |00659CB6|MyApp.exe |uROLocalServer.pas |TROLocalServer |SendRequest |57[1] | |00659CA4|MyApp.exe |uROLocalServer.pas |TROLocalServer |SendRequest |56[0] | |0065A009|MyApp.exe |uROLocalChannel.pas |TROLocalChannel |IntDispatch |99[10] | |005EE540|MyApp.exe |uROClient.pas |TROTransportChannel |Dispatch |1884[36] | |005EE3FC|MyApp.exe |uROClient.pas |TROTransportChannel |Dispatch |1848[0] | |005EEC8F|MyApp.exe |uROClient.pas |TROTransportChannel |Dispatch |2134[27] | |00616EC8|MyApp.exe |PCCS_Intf.pas |TSentrol_Proxy |GetNewValues |6585[7] | |007CBDB9|MyApp.exe |ETAROConnectionForm.pas |TROConnectionForm |SyncSentrolUpdateTimerTimer |855[16] | |7C82ABE5|ntdll.dll | | |RtlTimeToTimeFields | | |004D5D9C|MyApp.exe |Controls.pas |TControl |WndProc |5063[0] | |004DA05B|MyApp.exe |Controls.pas |TWinControl |WndProc |7304[111] | |7C81A3AB|ntdll.dll | | |RtlLeaveCriticalSection | | |0042659C|MyApp.exe |Classes.pas |TThreadList |UnlockList |3359[1] | |00426598|MyApp.exe |Classes.pas |TThreadList |UnlockList |3359[1] | |004935BC|MyApp.exe |Graphics.pas | |FreeMemoryContexts |5060[12] | |00493524|MyApp.exe |Graphics.pas | |FreeMemoryContexts |5048[0] | |004D9799|MyApp.exe |Controls.pas |TWinControl |MainWndProc |7076[6] | |004329F4|MyApp.exe |Classes.pas | |StdWndProc |11583[8] | |7739C09A|USER32.dll | | |CallNextHookEx | | |004B1343|MyApp.exe |ExtCtrls.pas |TTimer |Timer |2281[1] | |00404A30|MyApp.exe |system.pas | |_CallDynaInst |9159[1] | |004B1227|MyApp.exe |ExtCtrls.pas |TTimer |WndProc |2239[4] | |004329F4|MyApp.exe |Classes.pas | |StdWndProc |11583[8] | |7739C42C|USER32.dll | | |GetParent | | |7739C45C|USER32.dll | | |GetParent | | |773A16E0|USER32.dll | | |DispatchMessageA | | |773A16D6|USER32.dll | | |DispatchMessageA | | |004CC234|MyApp.exe |Forms.pas |TApplication |ProcessMessage |8105[23] | |004CC138|MyApp.exe |Forms.pas |TApplication |ProcessMessage |8082[0] | |004CC26E|MyApp.exe |Forms.pas |TApplication |HandleMessage |8124[1] | |004CC264|MyApp.exe |Forms.pas |TApplication |HandleMessage |8123[0] | |004CC563|MyApp.exe |Forms.pas |TApplication |Run |8223[20] | |004CC4B0|MyApp.exe |Forms.pas |TApplication |Run |8203[0] | |007F18B3|MyApp.exe |MyApp.dpr | | |215[65] | The stack trace seems to be ok until first TTimer call, after that it contains some garbage(?), however the end contains the the lock which seems be holding the main thread. Can I trust this stack trace? If not, what can cause this and how I can avoid it? Any ideas about the dead lock based on this stack trace? I don't quite understand how creating a datamodule can dead lock.. I'm using Delphi 2007.

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• All GIT Repos Corrupted on System Restore

  - by yar

  I restored my OSX today by copying the system over from a backup. Most things seem to be working, but every single GIT repo gives pretty much the same error fatal: object 03b45161eb27228914e690e032ca8009358e9588 is corrupted I have tried chowning, doing everything as sudo or root... I have no idea what to try next. This would be a normal git question except that it's on many repos. Ideas? Note: I'm using git 1.7.0.3 and I was probably using 1.7.0 before.

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• Malloc corrupting already malloc'd memory in C

  - by Kyte

  I'm currently helping a friend debug a program of his, which includes linked lists. His list structure is pretty simple: typedef struct nodo{ int cantUnos; char* numBin; struct nodo* sig; }Nodo; We've got the following code snippet: void insNodo(Nodo** lista, char* auxBin, int auxCantUnos){ printf("*******Insertando\n"); int i; if (*lista) printf("DecInt*%p->%p\n", *lista, (*lista)->sig); Nodo* insert = (Nodo*)malloc(sizeof(Nodo*)); if (*lista) printf("Malloc*%p->%p\n", *lista, (*lista)->sig); insert->cantUnos = auxCantUnos; insert->numBin = (char*)malloc(strlen(auxBin)*sizeof(char)); for(i=0 ; i<strlen(auxBin) ; i++) insert->numBin[i] = auxBin[i]; insert-numBin[i] = '\0'; insert-sig = NULL; Nodo* aux; [etc] (The lines with extra indentation were my addition for debug purposes) This yields me the following: *******Insertando DecInt*00341098->00000000 Malloc*00341098->2832B6EE (*lista)-sig is previously and deliberately set as NULL, which checks out until here, and fixed a potential buffer overflow (he'd forgotten to copy the NULL-terminator in insert-numBin). I can't think of a single reason why'd that happen, nor I've got any idea on what else should I provide as further info. (Compiling on latest stable MinGW under fully-patched Windows 7, friend's using MinGW under Windows XP. On my machine, at least, in only happens when GDB's not attached.) Any ideas? Suggestions? Possible exorcism techniques? (Current hack is copying the sig pointer to a temp variable and restore it after malloc. It breaks anyways. Turns out the 2nd malloc corrupts it too. Interestingly enough, it resets sig to the exact same value as the first one).

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• How do I corrupt a SQL CE Database?

  - by Peter Tate

  I want to be able to check for a corrupted database at startup, and then repair it programmatically. I can do that easily enough. My problem is that I want to test that things work the way I expect. Does anyone know of a way to purposefully corrupt a database so I can test my code?

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• Efficiently detect corrupted jpeg file?

  - by Jacco

  Is there an efficient way of detecting if a jpeg file is corrupted? Background info:   solutions needs to work from within a php script   the jpeg files are on disk   manual checking is no option (user uploaded data) I know that imagecreatefromjpeg(string $filename); can do it. But it is quite slow at doing so. Does anybody know a faster/more efficient solutions?

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• Is there a way to log when a particular memory location gets written and by which function?

  - by rusbi

  I'm having a bug in my c++ program which happens very rarely but crashes my program. It's seems I have some buffer overflow problem or something similar. I find that these types of bug are most difficult to find. My program always crashes because of the same corrupted memory location. I'm wondering if there is some debugging tool which could detect when a particular memory location get written to and logs the function which does it. I'm using VLD (visual leak detector) for my memory leak hunting and it works great. It substitutes the original mallocs which its own and logs every allocation. I was wondering if there is something similar for memory? I know that something like that would cripple a program, but it could be really helpful.

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• Averaging corrupted images to eliminate the noise

  - by Mertie Pertie

  Hi all As you can get it from the title, I want to average some .jpg images which are corrupted by zero-mean Gaussian additive. After searching over internet, I figured out to add image matrices and divide the sum by the # of matrices. However the resultant image is totally black. Normally when the number of image increases then the resultant image gets better. But When I use more images it gets darker. I am using 800x600 black and white images with .jpg ext Here is the script I used; image1 = imread ('PIC1.jpg'); image2 = imread ('PIC2.jpg'); image3 = imread ('PIC3.jpg'); image4 = imread ('PIC4.jpg'); sum = image1 + image2 + image3 + image4; av = sum / 4; imshow(av); Thanks in advance

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• Problem with averaging corrupted images to eliminate the noise in MATLAB

  - by Mertie Pertie

  I want to average some .jpg images which are corrupted by zero-mean Gaussian additive noise. After searching around, I figured out to add the image matrices and divide the sum by the number of matrices. However, the resultant image is totally black. Normally when the number of image increases then the resultant image gets better. But when I use more images it gets darker. I am using 800x600 black and white .jpg images. Here is the script I used: image1 = imread ('PIC1.jpg'); image2 = imread ('PIC2.jpg'); image3 = imread ('PIC3.jpg'); image4 = imread ('PIC4.jpg'); sum = image1 + image2 + image3 + image4; av = sum / 4; imshow(av);

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• Averaging corrupted images to eliminate the noise in Matlab

  - by Mertie Pertie

  Hi all As you can get it from the title, I want to average some .jpg images which are corrupted by zero-mean Gaussian additive. After searching over internet, I figured out to add image matrices and divide the sum by the # of matrices. However the resultant image is totally black. Normally when the number of image increases then the resultant image gets better. But When I use more images it gets darker. I am using 800x600 black and white images with .jpg ext Here is the script I used; image1 = imread ('PIC1.jpg'); image2 = imread ('PIC2.jpg'); image3 = imread ('PIC3.jpg'); image4 = imread ('PIC4.jpg'); sum = image1 + image2 + image3 + image4; av = sum / 4; imshow(av); Thanks in advance

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• C++ -malign-double compiler flag

  - by Martin

  I need some help on compiler flags in c++. I'm using a library that is a port to linux from windows, that has to be compiled with the -malign-double flag, "for Win32 compatibility". It's my understanding that this mean I absolutely have to compile my own code with this flag as well? How about other .so shared libraries, do they have be recompiled with this flag as well? If so, is there any way around this? I'm a linux newbie (and c++), so even though I tried to recompile all the libraries I'm using for my project, it was just too complicated to recursively find the source for all the libraries and the libraries they're dependent on, and recompile everything.

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• Open + Save .exe file in notepad makes it corrupted

  - by Jacob Kofoed

  Hi, I just published this simple console application that is supposed to show a textbox with the value of a setting called "userID" with value 1001. This works like a charm. Now what I need is to change this value outside the editor, from notepad etc. When I open the application a lot in there is non-sence (& o! -å Þþþ,o" Ü+) etc. but with a quick (ctrl + F) I found the value 1001, and changed this to some other integer. I ran the application again, and it failed, didn't even give any userful error-message. At a point I tried just opening a newly published non-corrupted version of the application, didn't change anything, then saved from notepad, and it were also corrupted. It seems like notepad can't open some characters or something. Do I need to publish the application in some specific text-unicode language or something? Help much appreciated :) I know it sounds like a stupid application, but it is just a test of concept :) I use vb.net for this

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• std::string constructor corrupts pointer

  - by computergeek6

  I have an Entity class, which contains 3 pointers: m_rigidBody, m_entity, and m_parent. Somewhere in Entity::setModel(std::string model), it's crashing. Apparently, this is caused by bad data in m_entity. The weird thing is that I nulled it in the constructor and haven't touched it since then. I debugged it and put a watchpoint on it, and it comes up that the m_entity member is being changed in the constructor for std::string that's being called while converting a const char* into an std::string for the setModel call. I'm running on a Mac, if that helps (I think I remember some problem with std::string on the Mac). Any ideas about what's going on?

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• PHP IIS problems downloading file says it is corrupt

  - by Matt

  Hi, I am running PHP on IIS 6 with mssql. I have uploaded a file to my webserver through a php script. Upon checking the file on the server the file is ok and not corrupt. However, when i then have a link on my website to try and download the file, it says the file is corrupt. I know the file isnt corrupt as i can view it perfectly if i look at the file on the server. Is seems like this is a common problem as a similar problem was posted here: http://www.bigresource.com/Tracker/Track-php-1pAakBhT/ Any help would be much appreciated. Thanks, M My download code is as follows: $filesize = $rows->filesize; $filepath = $rows->filepath; header("Content-Disposition: attachment; filename=$filename"); header("Content-length: $filesize"); header("Content-type: application/pdf"); header("Cache-control: must-revalidate"); header("Content-Description: PHP Generated Data"); readfile($filepath);

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• How to diagnose, and reverse (not prevent) Unicode mangling

  - by Steve Bennett

  Somewhere upstream of me, "something" happened that looks like unicode mangling. One symptom is that a lowercase u umlaut (ü) gets converted to "ü" (ie, character FC gets converted to C3 BC). Assuming that I have no control over this upstream process, how can I reverse-engineer what's going on? And if that is possible, can I crank the sausage machine backwards and get the original text back? (If it helps to understand this case, the text I received was in the form of a MySQL dump. I think somwewhere in the dump/transport process it got mangled.)

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• Writing to pointer out of bounds after malloc() not causing error

  - by marr

  Hi, when I try the code below it works fine. Am I missing something? main() { int *p; p=malloc(sizeof(int)); printf("size of p=%d\n",sizeof(p)); p[500]=999999; printf("p[0]=%d",p[500]); return 0; } I tried it with malloc(0*sizeof(int)) or anything but it works just fine. The program only crashes when I don't use malloc at all. So even if I allocate 0 memory for the array p, it still stores values properly. So why am I even bothering with malloc then?

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• Neo4j OutOfMemory problem

  - by Edward83

  Hi! This is my source code of Main.java. It was grabbed from neo4j-apoc-1.0 examples. The goal of modification to store 1M records of 2 nodes and 1 relation: package javaapplication2; import org.neo4j.graphdb.GraphDatabaseService; import org.neo4j.graphdb.Node; import org.neo4j.graphdb.RelationshipType; import org.neo4j.graphdb.Transaction; import org.neo4j.kernel.EmbeddedGraphDatabase; public class Main { private static final String DB_PATH = "neo4j-store-1M"; private static final String NAME_KEY = "name"; private static enum ExampleRelationshipTypes implements RelationshipType { EXAMPLE } public static void main(String[] args) { GraphDatabaseService graphDb = null; try { System.out.println( "Init database..." ); graphDb = new EmbeddedGraphDatabase( DB_PATH ); registerShutdownHook( graphDb ); System.out.println( "Start of creating database..." ); int valIndex = 0; for(int i=0; i<1000; ++i) { for(int j=0; j<1000; ++j) { Transaction tx = graphDb.beginTx(); try { Node firstNode = graphDb.createNode(); firstNode.setProperty( NAME_KEY, "Hello" + valIndex ); Node secondNode = graphDb.createNode(); secondNode.setProperty( NAME_KEY, "World" + valIndex ); firstNode.createRelationshipTo( secondNode, ExampleRelationshipTypes.EXAMPLE ); tx.success(); ++valIndex; } finally { tx.finish(); } } } System.out.println("Ok, client processing finished!"); } finally { System.out.println( "Shutting down database ..." ); graphDb.shutdown(); } } private static void registerShutdownHook( final GraphDatabaseService graphDb ) { // Registers a shutdown hook for the Neo4j instance so that it // shuts down nicely when the VM exits (even if you "Ctrl-C" the // running example before it's completed) Runtime.getRuntime().addShutdownHook( new Thread() { @Override public void run() { graphDb.shutdown(); } } ); } } After a few iterations (around 150K) I got error message: "java.lang.OutOfMemoryError: Java heap space at java.nio.HeapByteBuffer.(HeapByteBuffer.java:39) at java.nio.ByteBuffer.allocate(ByteBuffer.java:312) at org.neo4j.kernel.impl.nioneo.store.PlainPersistenceWindow.(PlainPersistenceWindow.java:30) at org.neo4j.kernel.impl.nioneo.store.PersistenceWindowPool.allocateNewWindow(PersistenceWindowPool.java:534) at org.neo4j.kernel.impl.nioneo.store.PersistenceWindowPool.refreshBricks(PersistenceWindowPool.java:430) at org.neo4j.kernel.impl.nioneo.store.PersistenceWindowPool.acquire(PersistenceWindowPool.java:122) at org.neo4j.kernel.impl.nioneo.store.CommonAbstractStore.acquireWindow(CommonAbstractStore.java:459) at org.neo4j.kernel.impl.nioneo.store.AbstractDynamicStore.updateRecord(AbstractDynamicStore.java:240) at org.neo4j.kernel.impl.nioneo.store.PropertyStore.updateRecord(PropertyStore.java:209) at org.neo4j.kernel.impl.nioneo.xa.Command$PropertyCommand.execute(Command.java:513) at org.neo4j.kernel.impl.nioneo.xa.NeoTransaction.doCommit(NeoTransaction.java:443) at org.neo4j.kernel.impl.transaction.xaframework.XaTransaction.commit(XaTransaction.java:316) at org.neo4j.kernel.impl.transaction.xaframework.XaResourceManager.commit(XaResourceManager.java:399) at org.neo4j.kernel.impl.transaction.xaframework.XaResourceHelpImpl.commit(XaResourceHelpImpl.java:64) at org.neo4j.kernel.impl.transaction.TransactionImpl.doCommit(TransactionImpl.java:514) at org.neo4j.kernel.impl.transaction.TxManager.commit(TxManager.java:571) at org.neo4j.kernel.impl.transaction.TxManager.commit(TxManager.java:543) at org.neo4j.kernel.impl.transaction.TransactionImpl.commit(TransactionImpl.java:102) at org.neo4j.kernel.EmbeddedGraphDbImpl$TransactionImpl.finish(EmbeddedGraphDbImpl.java:329) at javaapplication2.Main.main(Main.java:62) 28.05.2010 9:52:14 org.neo4j.kernel.impl.nioneo.store.PersistenceWindowPool logWarn WARNING: [neo4j-store-1M\neostore.propertystore.db.strings] Unable to allocate direct buffer" Guys! Help me plzzz, what I did wrong, how can I repair it? Tested on platform Windows XP 32bit SP3. Maybe solution within creation custom configuration? thnx 4 every advice!

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• Can I set Java max heap size for running from a jar file?

  - by Kip

  I am launching a java jar file which often requires more than the default 64MB max heap size. A 256MB heap size is sufficient for this app though. Is there anyway to specify (in the manifest maybe?) to always use a 256MB max heap size when launching the jar? (More specific details below, if needed.) This is a command-line app that I've written in Java, which does some image manipulation. On high-res images (about 12 megapixels and above, which is not uncommon) I get an OutOfMemoryError. Currently I'm launching the app from a jar file, i.e. java -jar MyApp.jar params... I can avoid an OutOfMemoryError by specifying 256MB max heap size on the command line, i.e.: java -Xmx256m -jar MyApp.jar params... However, I don't want to have to specify this, since I know that 256MB is sufficient even for high-res images. I'd like to have that information saved in the jar file. Is that possible?

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• weblogic 9 - best way of manually forcing a heap dump - not at OOM.

  - by monojohnny

  Is there a simple commandline that can be issued to weblogic 9.2 to force the JVM to produce a heap dump ? Thanks,

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• Sorting Algorithms

  - by MarkPearl

  General Every time I go back to university I find myself wading through sorting algorithms and their implementation in C++. Up to now I haven’t really appreciated their true value. However as I discovered this last week with Dictionaries in C# – having a knowledge of some basic programming principles can greatly improve the performance of a system and make one think twice about how to tackle a problem. I’m going to cover briefly in this post the following: Selection Sort Insertion Sort Shellsort Quicksort Mergesort Heapsort (not complete) Selection Sort Array based selection sort is a simple approach to sorting an unsorted array. Simply put, it repeats two basic steps to achieve a sorted collection. It starts with a collection of data and repeatedly parses it, each time sorting out one element and reducing the size of the next iteration of parsed data by one. So the first iteration would go something like this… Go through the entire array of data and find the lowest value Place the value at the front of the array The second iteration would go something like this… Go through the array from position two (position one has already been sorted with the smallest value) and find the next lowest value in the array. Place the value at the second position in the array This process would be completed until the entire array had been sorted. A positive about selection sort is that it does not make many item movements. In fact, in a worst case scenario every items is only moved once. Selection sort is however a comparison intensive sort. If you had 10 items in a collection, just to parse the collection you would have 10+9+8+7+6+5+4+3+2=54 comparisons to sort regardless of how sorted the collection was to start with. If you think about it, if you applied selection sort to a collection already sorted, you would still perform relatively the same number of iterations as if it was not sorted at all. Many of the following algorithms try and reduce the number of comparisons if the list is already sorted – leaving one with a best case and worst case scenario for comparisons. Likewise different approaches have different levels of item movement. Depending on what is more expensive, one may give priority to one approach compared to another based on what is more expensive, a comparison or a item move. Insertion Sort Insertion sort tries to reduce the number of key comparisons it performs compared to selection sort by not “doing anything” if things are sorted. Assume you had an collection of numbers in the following order… 10 18 25 30 23 17 45 35 There are 8 elements in the list. If we were to start at the front of the list – 10 18 25 & 30 are already sorted. Element 5 (23) however is smaller than element 4 (30) and so needs to be repositioned. We do this by copying the value at element 5 to a temporary holder, and then begin shifting the elements before it up one. So… Element 5 would be copied to a temporary holder 10 18 25 30 23 17 45 35 – T 23 Element 4 would shift to Element 5 10 18 25 30 30 17 45 35 – T 23 Element 3 would shift to Element 4 10 18 25 25 30 17 45 35 – T 23 Element 2 (18) is smaller than the temporary holder so we put the temporary holder value into Element 3. 10 18 23 25 30 17 45 35 – T 23   We now have a sorted list up to element 6. And so we would repeat the same process by moving element 6 to a temporary value and then shifting everything up by one from element 2 to element 5. As you can see, one major setback for this technique is the shifting values up one – this is because up to now we have been considering the collection to be an array. If however the collection was a linked list, we would not need to shift values up, but merely remove the link from the unsorted value and “reinsert” it in a sorted position. Which would reduce the number of transactions performed on the collection. So.. Insertion sort seems to perform better than selection sort – however an implementation is slightly more complicated. This is typical with most sorting algorithms – generally, greater performance leads to greater complexity. Also, insertion sort performs better if a collection of data is already sorted. If for instance you were handed a sorted collection of size n, then only n number of comparisons would need to be performed to verify that it is sorted. It’s important to note that insertion sort (array based) performs a number item moves – every time an item is “out of place” several items before it get shifted up. Shellsort – Diminishing Increment Sort So up to now we have covered Selection Sort & Insertion Sort. Selection Sort makes many comparisons and insertion sort (with an array) has the potential of making many item movements. Shellsort is an approach that takes the normal insertion sort and tries to reduce the number of item movements. In Shellsort, elements in a collection are viewed as sub-collections of a particular size. Each sub-collection is sorted so that the elements that are far apart move closer to their final position. Suppose we had a collection of 15 elements… 10 20 15 45 36 48 7 60 18 50 2 19 43 30 55 First we may view the collection as 7 sub-collections and sort each sublist, lets say at intervals of 7 10 60 55 – 20 18 – 15 50 – 45 2 – 36 19 – 48 43 – 7 30 10 55 60 – 18 20 – 15 50 – 2 45 – 19 36 – 43 48 – 7 30 (Sorted) We then sort each sublist at a smaller inter – lets say 4 10 55 60 18 – 20 15 50 2 – 45 19 36 43 – 48 7 30 10 18 55 60 – 2 15 20 50 – 19 36 43 45 – 7 30 48 (Sorted) We then sort elements at a distance of 1 (i.e. we apply a normal insertion sort) 10 18 55 60 2 15 20 50 19 36 43 45 7 30 48 2 7 10 15 18 19 20 30 36 43 45 48 50 55 (Sorted) The important thing with shellsort is deciding on the increment sequence of each sub-collection. From what I can tell, there isn’t any definitive method and depending on the order of your elements, different increment sequences may perform better than others. There are however certain increment sequences that you may want to avoid. An even based increment sequence (e.g. 2 4 8 16 32 …) should typically be avoided because it does not allow for even elements to be compared with odd elements until the final sort phase – which in a way would negate many of the benefits of using sub-collections. The performance on the number of comparisons and item movements of Shellsort is hard to determine, however it is considered to be considerably better than the normal insertion sort. Quicksort Quicksort uses a divide and conquer approach to sort a collection of items. The collection is divided into two sub-collections – and the two sub-collections are sorted and combined into one list in such a way that the combined list is sorted. The algorithm is in general pseudo code below… Divide the collection into two sub-collections Quicksort the lower sub-collection Quicksort the upper sub-collection Combine the lower & upper sub-collection together As hinted at above, quicksort uses recursion in its implementation. The real trick with quicksort is to get the lower and upper sub-collections to be of equal size. The size of a sub-collection is determined by what value the pivot is. Once a pivot is determined, one would partition to sub-collections and then repeat the process on each sub collection until you reach the base case. With quicksort, the work is done when dividing the sub-collections into lower & upper collections. The actual combining of the lower & upper sub-collections at the end is relatively simple since every element in the lower sub-collection is smaller than the smallest element in the upper sub-collection. Mergesort With quicksort, the average-case complexity was O(nlog2n) however the worst case complexity was still O(N*N). Mergesort improves on quicksort by always having a complexity of O(nlog2n) regardless of the best or worst case. So how does it do this? Mergesort makes use of the divide and conquer approach to partition a collection into two sub-collections. It then sorts each sub-collection and combines the sorted sub-collections into one sorted collection. The general algorithm for mergesort is as follows… Divide the collection into two sub-collections Mergesort the first sub-collection Mergesort the second sub-collection Merge the first sub-collection and the second sub-collection As you can see.. it still pretty much looks like quicksort – so lets see where it differs… Firstly, mergesort differs from quicksort in how it partitions the sub-collections. Instead of having a pivot – merge sort partitions each sub-collection based on size so that the first and second sub-collection of relatively the same size. This dividing keeps getting repeated until the sub-collections are the size of a single element. If a sub-collection is one element in size – it is now sorted! So the trick is how do we put all these sub-collections together so that they maintain their sorted order. Sorted sub-collections are merged into a sorted collection by comparing the elements of the sub-collection and then adjusting the sorted collection. Lets have a look at a few examples… Assume 2 sub-collections with 1 element each 10 & 20 Compare the first element of the first sub-collection with the first element of the second sub-collection. Take the smallest of the two and place it as the first element in the sorted collection. In this scenario 10 is smaller than 20 so 10 is taken from sub-collection 1 leaving that sub-collection empty, which means by default the next smallest element is in sub-collection 2 (20). So the sorted collection would be 10 20 Lets assume 2 sub-collections with 2 elements each 10 20 & 15 19 So… again we would Compare 10 with 15 – 10 is the winner so we add it to our sorted collection (10) leaving us with 20 & 15 19 Compare 20 with 15 – 15 is the winner so we add it to our sorted collection (10 15) leaving us with 20 & 19 Compare 20 with 19 – 19 is the winner so we add it to our sorted collection (10 15 19) leaving us with 20 & _ 20 is by default the winner so our sorted collection is 10 15 19 20. Make sense? Heapsort (still needs to be completed) So by now I am tired of sorting algorithms and trying to remember why they were so important. I think every year I go through this stuff I wonder to myself why are we made to learn about selection sort and insertion sort if they are so bad – why didn’t we just skip to Mergesort & Quicksort. I guess the only explanation I have for this is that sometimes you learn things so that you can implement them in future – and other times you learn things so that you know it isn’t the best way of implementing things and that you don’t need to implement it in future. Anyhow… luckily this is going to be the last one of my sorts for today. The first step in heapsort is to convert a collection of data into a heap. After the data is converted into a heap, sorting begins… So what is the definition of a heap? If we have to convert a collection of data into a heap, how do we know when it is a heap and when it is not? The definition of a heap is as follows: A heap is a list in which each element contains a key, such that the key in the element at position k in the list is at least as large as the key in the element at position 2k +1 (if it exists) and 2k + 2 (if it exists). Does that make sense? At first glance I’m thinking what the heck??? But then after re-reading my notes I see that we are doing something different – up to now we have really looked at data as an array or sequential collection of data that we need to sort – a heap represents data in a slightly different way – although the data is stored in a sequential collection, for a sequential collection of data to be in a valid heap – it is “semi sorted”. Let me try and explain a bit further with an example… Example 1 of Potential Heap Data Assume we had a collection of numbers as follows 1[1] 2[2] 3[3] 4[4] 5[5] 6[6] For this to be a valid heap element with value of 1 at position [1] needs to be greater or equal to the element at position [3] (2k +1) and position [4] (2k +2). So in the above example, the collection of numbers is not in a valid heap. Example 2 of Potential Heap Data Lets look at another collection of numbers as follows 6[1] 5[2] 4[3] 3[4] 2[5] 1[6] Is this a valid heap? Well… element with the value 6 at position 1 must be greater or equal to the element at position [3] and position [4]. Is 6 > 4 and 6 > 3? Yes it is. Lets look at element 5 as position 2. It must be greater than the values at [4] & [5]. Is 5 > 3 and 5 > 2? Yes it is. If you continued to examine this second collection of data you would find that it is in a valid heap based on the definition of a heap.

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• What do I use for a max-heap implementation in Python?

  - by Douglas Mayle

  Python includes the heapq module for min-heaps, but I need a max heap. What should I use for a max-heap implementation in Python?

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• What's the differences between VirtualAlloc and HeapAlloc?

  - by Jinx

  There are lots of method to allocate memory in windows enviorment, such as VirtualAlloc/HeapAlloc/malloc/new. Thus , what's the difference among them?

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• Java -Xms initial size effects

  - by SyBer

  Hi. What is the benefit of setting the -Xms parameter, and having the initial memory larger for example, then the default calculated one (64 MB in my case, according to Java GC tunning: http://java.sun.com/javase/technologies/hotspot/gc/gc_tuning_6.html#par_gc.ergonomics.default_size)? Also, is there any good to setting both the initial and maximum memories to same size? Thanks.

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