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  • How are you taking advantage of Multicore?

    - by tgamblin
    As someone in the world of HPC who came from the world of enterprise web development, I'm always curious to see how developers back in the "real world" are taking advantage of parallel computing. This is much more relevant now that all chips are going multicore, and it'll be even more relevant when there are thousands of cores on a chip instead of just a few. My questions are: How does this affect your software roadmap? I'm particularly interested in real stories about how multicore is affecting different software domains, so specify what kind of development you do in your answer (e.g. server side, client-side apps, scientific computing, etc). What are you doing with your existing code to take advantage of multicore machines, and what challenges have you faced? Are you using OpenMP, Erlang, Haskell, CUDA, TBB, UPC or something else? What do you plan to do as concurrency levels continue to increase, and how will you deal with hundreds or thousands of cores? If your domain doesn't easily benefit from parallel computation, then explaining why is interesting, too. Finally, I've framed this as a multicore question, but feel free to talk about other types of parallel computing. If you're porting part of your app to use MapReduce, or if MPI on large clusters is the paradigm for you, then definitely mention that, too. Update: If you do answer #5, mention whether you think things will change if there get to be more cores (100, 1000, etc) than you can feed with available memory bandwidth (seeing as how bandwidth is getting smaller and smaller per core). Can you still use the remaining cores for your application?

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  • theoretical and practical matrix multiplication FLOP

    - by mjr
    I wrote traditional matrix multiplication in c++ and tried to measure and compare its theoretical and practical FLOP. As I know inner loop of MM has 2 operation therefore simple MM theoretical Flops is 2*n*n*n (2n^3) but in practice I get something like 4n^3 + number of operation which is 2 i.e. 6n^3 also if I just try to add up only one array a[i][j]++ practical flops then calculate like 3n^3 and not n^3 as you see again it is 2n^3 +1 operation and not 1 operation * n^3 . This is in case if I use 1D array in three nested loops as Matrix multiplication and compare flop, practical flop is the same (near) the theoretical flop and depend exactly as the number of operation in inner loop.I could not find the reason for this behaviour. what is the reason in both case? I know that theoretical flop is not the same as practical one because of some operations like load etc. system specification: Intel core2duo E4500 3700g memory L2 cache 2M x64 fedora 17 sample results: Matrix matrix multiplication 512*512 Real_time: 1.718368 Proc_time: 1.227672 Total flpops: 807,107,072 MFLOPS: 657.429016 Real_time: 3.608078 Proc_time: 3.042272 Total flpops: 807,024,448 MFLOPS: 265.270355 theoretical flop: 2*512*512*512=268,435,456 Practical flops= 6*512^3 =807,107,072 Using 1 dimensional array float d[size][size]:512 or any size for (int j = 0; j < size; ++j) { for (int k = 0; k < size; ++k) { d[k]=d[k]+e[k]+f[k]+g[k]+r; } } Real_time: 0.002288 Proc_time: 0.002260 Total flpops: 1,048,578 MFLOPS: 464.027161 theroretical flop: *4n^2=4*512^2=1,048,576* practical flop : 4n^2+overhead (other operation?)=1,048,578 3 loop version: Real_time: 1.282257 Proc_time: 1.155990 Total flpops: 536,872,000 MFLOPS: 464.426117 theoretical flop:4n^3 = 536,870,912 practical flop: *4n^3=4*512^3+overheads(other operation?)=536,872,000* thank you

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  • Question - Setting dynamic HTML using Javascript to iFrames on Windows Mobile 6.1 - IE Mobile6

    - by swaroop
    Hi Experts, (excuse me if this is not the right forum to post - i couldn't find anything related to non-native programming and related to this topic) I Am trying to set a dynamic HTML into an iFrame on the webpage. I have tried a couple of things but none of them seem to work. I m able to read the innerHTML but can't seem to update it. // Able to read using document.getElementById('iFrameIdentifier').innerHTML; // On Desktop IE, this code works document.getElementById('iFrameId').contentWindow.document.open(); document.getElementById('iFrameId').contentWindow.document.write(dynamicHTML); document.getElementById('iFrameId').contentWindow.document.close(); Ideally the same function should work as how it works for div's but it says 'Object doesn't support this method or property". I have also tried document.getElementById('iFrameId').document.body.innerHTML. This apparently replaces the whole HTML of the page and not just the innerHTML. I have tried out a couple of things and they didn't work document.getElementById('iFrameId').body.innerHTML document.frames[0].document.body.innerHTML My purpose is to have a container element which can contain dynamic HTML that's set to it. I've been using it well till now when I observed that the setting innerHTML on a div is taking increasing amount of time because of the onClicks or other JS methods that are attached to the anchors and images in the dynamic HTML. Appears the JS methods or the HTML is some how not getting cleaned up properly (memory leak?) Also being discussed - http://www.experts-exchange.com/Programming/Languages/Scripting/JavaScript/Q_26185526.html#a32779090

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  • RegistryKey ValueCount/SubKeyCount wrong

    - by Mark J Miller
    I am trying to query the following registry key values: HKLM\SOFTWARE\Microsoft\MSSQLServer\Client\SharedMemoryOn HKLM\SOFTWARE\Microsoft\MSSQLServer\Client\SuperSocketNetLib\ProtocolOrder But depending on which machine I'm running the program the query returns null. When I debug on my local machine and I inspect the value for ValueCount for: HKLM\SOFTWARE\Microsoft\MSSQLServer\Client HKLM\SOFTWARE\Microsoft\MSSQLServer\Client\SuperSocketNetLib The count is 0 and OpenSubKey returns null. I am a domain admin, in the local administrators group and have added the following to my app.manifest: <requestedExecutionLevel level="requireAdministrator" uiAccess="false" /> Any idea why? private static void ValidateSqlClientSettings() { Console.WriteLine("\r\n/////////////// LOCAL SQL CLIENT PROTOCOLS ////////////////"); RegistryKey keyHKLM = Registry.LocalMachine; ///TODO: nullreferenceexception - connect to remote machine and find out why RegistryKey sqlClientKey = keyHKLM.OpenSubKey(@"SOFTWARE\Microsoft\MSSQLServer\Client"); if (sqlClientKey == null) { WriteLine2Console(@"WARNING: unable to read registry key '{0}\SOFTWARE\Microsoft\MSSQLServer\Client'", ConsoleColor.Yellow); } var cliKeyNames = from k in sqlClientKey.GetSubKeyNames() where k == "SuperSocketNetLib" select k; ///TODO: find out why these values are always missing (even if I can see them in regedit) Console.Write("Shared Memory Disabled (cliconfg): "); if (Convert.ToBoolean(sqlClientKey.GetValue("SharedMemoryOn"))) WriteLine2Console("FAILED", ConsoleColor.Red); else if(sqlClientKey.GetValue("SharedMemoryOn") == null) WriteLine2Console(String.Format("WARNING - unable to read '{0}\\SharedMemoryOn'", sqlClientKey.Name), ConsoleColor.Yellow); else WriteLine2Console("PASS", ConsoleColor.Green); Console.Write("Client Protocol Order (cliconfg - tcp first): "); foreach (string cliKey in cliKeyNames) { RegistryKey subKey = sqlClientKey.OpenSubKey(cliKey); object order = subKey.GetValue("ProtocolOrder"); if (order != null && order.ToString().StartsWith("tcp") == false) { WriteLine2Console("FAILED", ConsoleColor.Red); } else if (order == null) { WriteLine2Console(String.Format("WARNING - unable to read '{0}\\ProtocolOrder'", subKey.Name), ConsoleColor.Yellow); } else { WriteLine2Console("PASS", ConsoleColor.Green); } subKey.Close(); } sqlClientKey.Close(); keyHKLM.Close(); }

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  • "QFontEngine(Win) GetTextMetrics failed ()" error on 64-bit Windows

    - by David Murdoch
    I'll add 500 of my own rep as a bounty when SO lets me. I'm using wkhtmltopdf to convert HTML web pages to PDFs. This works perfectly on my 32-bit dev server [unfortunately, I can't ship my machine :-p ]. However, when I deploy to the web application's 64-bit server the following errors are displayed: C:\>wkhtmltopdf http://www.google.com google.pdf Loading pages (1/5) QFontEngine::loadEngine: GetTextMetrics failed () ] 10% QFontEngineWin: GetTextMetrics failed () QFontEngineWin: GetTextMetrics failed () QFontEngine::loadEngine: GetTextMetrics failed () QFontEngineWin: GetTextMetrics failed () QFontEngineWin: GetTextMetrics failed () QFontEngineWin: GetTextMetrics failed () QFontEngine::loadEngine: GetTextMetrics failed () ] 36% QFontEngineWin: GetTextMetrics failed () QFontEngineWin: GetTextMetrics failed () // ...etc.... and the PDF is created and saved... just WITHOUT text. All form-fields, images, borders, tables, divs, spans, ps, etc are rendered accurately...just void of any text at all. Server information: Windows edition: Windows Server Standard Service Pack 2 Processor: Intel Xeon E5410 @ 2.33GHz 2.33 GHz Memory: 8.00 GB System type: 64-bit Operating System Can anyone give me a clue as to what is happening and how I can fix this? Also, I wasn't sure what to tag/title this question with...so if you can think of better tags/title comment them or edit the question. :-)

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  • x86 CMP Instruction Difference

    - by Pindatjuh
    Question What is the (non-trivial) difference between the following two x86 instructions? 39 /r CMP r/m32,r32 Compare r32 with r/m32 3B /r CMP r32,r/m32 Compare r/m32 with r32 Background I'm building a Java assembler, which will be used by my compiler's intermediate language to produce Windows-32 executables. Currently I have following code: final ModelBase mb = new ModelBase(); // create new memory model mb.addCode(new Compare(Register.ECX, Register.EAX)); // add code mb.addCode(new Compare(Register.EAX, Register.ECX)); // add code final FileOutputStream fos = new FileOutputStream(new File("test.exe")); mb.writeToFile(fos); fos.close(); To output a valid executable file, which contains two CMP instruction in a TEXT-section. The executable outputted to "text.exe" will do nothing interesting, but that's not the point. The class Compare is a wrapper around the CMP instruction. The above code produces (inspecting with OllyDbg): Address Hex dump Command 0040101F |. 3BC8 CMP ECX,EAX 00401021 |. 3BC1 CMP EAX,ECX The difference is subtle: if I use the 39 byte-opcode: Address Hex dump Command 0040101F |. 39C1 CMP ECX,EAX 00401021 |. 39C8 CMP EAX,ECX Which makes me wonder about their synonymity and why this even exists.

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  • JSON: Jackson stream parser - is it really worth it?

    - by synic
    I'm making pretty heavy use of JSON parsing in an app I'm writing. Most of what I have done is already implemented using Android's built in JSONObject library (is it json-lib?). JSONObject appears to create instances of absolutely everything in the JSON string... even if I don't end up using all of them. My app currently runs pretty well, even on a G1. My question is this: are the speed and memory benefits from using a stream parser like Jackson worth all the trouble? By trouble, I mean this: As far as I can tell, there are three downsides to using Jackson instead of the built in library: Dependency on an external library. This makes your .apk bigger in the end. Not a huge deal. Your app is more fragile. Since the parsing is not done automatically, it is more vulnerable to changes in the JSON text that it's parsing. I'm extremely worried that malformed JSON will result in infinite loops (as pull parsing requires a lot of while loops). Writing code to parse JSON via a stream parser is ugly and tedious.

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  • Required Working Precision for the BBP Algorithm?

    - by brainfsck
    Hello, I'm looking to compute the nth digit of Pi in a low-memory environment. As I don't have decimals available to me, this integer-only BBP algorithm in Python has been a great starting point. I only need to calculate one digit of Pi at a time. How can I determine the lowest I can set D, the "number of digits of working precision"? D=4 gives me many correct digits, but a few digits will be off by one. For example, computing digit 393 with precision of 4 gives me 0xafda, from which I extract the digit 0xa. However, the correct digit is 0xb. No matter how high I set D, it seems that testing a sufficient number of digits finds an one where the formula returns an incorrect value. I've tried upping the precision when the digit is "close" to another, e.g. 0x3fff or 0x1000, but cannot find any good definition of "close"; for instance, calculating at digit 9798 gives me 0xcde6 , which is not very close to 0xd000, but the correct digit is 0xd. Can anyone help me figure out how much working precision is needed to calculate a given digit using this algorithm? Thank you,

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  • Boost.MultiIndex: Are there way to share object between two processes?

    - by Arman
    Hello, I have a Boost.MultiIndex big array about 10Gb. In order to reduce the reading I thought there should be a way to keep the data in the memory and another client programs will be able to read and analyse it. What is the proper way to organize it? The array looks like: struct particleID { int ID;// real ID for particle from Gadget2 file "ID" block unsigned int IDf;// postition in the file particleID(int id,const unsigned int idf):ID(id),IDf(idf){} bool operator<(const particleID& p)const { return ID<p.ID;} unsigned int getByGID()const {return (ID&0x0FFF);}; }; struct ID{}; struct IDf{}; struct IDg{}; typedef multi_index_container< particleID, indexed_by< ordered_unique< tag<IDf>, BOOST_MULTI_INDEX_MEMBER(particleID,unsigned int,IDf)>, ordered_non_unique< tag<ID>,BOOST_MULTI_INDEX_MEMBER(particleID,int,ID)>, ordered_non_unique< tag<IDg>,BOOST_MULTI_INDEX_CONST_MEM_FUN(particleID,unsigned int,getByGID)> > > particlesID_set; Any ideas are welcome. kind regards Arman.

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  • AST with fixed nodes instead of error nodes in antlr

    - by ahe
    I have an antlr generated Java parser that uses the C target and it works quite well. The problem is I also want it to parse erroneous code and produce a meaningful AST. If I feed it a minimal Java class with one import after which a semicolon is missing it produces two "Tree Error Node" objects where the "import" token and the tokens for the imported class should be. But since it parses the following code correctly and produces the correct nodes for this code it must recover from the error by adding the semicolon or by resyncing. Is there a way to make antlr reflect this fixed input it produces internally in the AST? Or can I at least get the tokens/text that produced the "Tree Node Errors" somehow? In the C targets antlr3commontreeadaptor.c around line 200 the following fragment indicates that the C target only creates dummy error nodes so far: static pANTLR3_BASE_TREE errorNode (pANTLR3_BASE_TREE_ADAPTOR adaptor, pANTLR3_TOKEN_STREAM ctnstream, pANTLR3_COMMON_TOKEN startToken, pANTLR3_COMMON_TOKEN stopToken, pANTLR3_EXCEPTION e) { // Use the supplied common tree node stream to get another tree from the factory // TODO: Look at creating the erronode as in Java, but this is complicated by the // need to track and free the memory allocated to it, so for now, we just // want something in the tree that isn't a NULL pointer. // return adaptor->createTypeText(adaptor, ANTLR3_TOKEN_INVALID, (pANTLR3_UINT8)"Tree Error Node"); } Am I out of luck here and only the error nodes the Java target produces would allow me to retrieve the text of the erroneous nodes?

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  • Getting EXC_BAD_ACCESS without any helpful msg from NSZombieEnabled

    - by nefsu
    Hello guys. I'm a newbie to iphone development and I've been struggling with an EXC_BAD_ACCESS error I got a couple of days ago. I'm basically taking the Stanford iphone class independently and I am trying to pass an array of NSManagedObjects to a TableViewController that's supposed to display them. The application launches in the simulator and displays the data in the tableView but it immediately errors out with an EXC_BAD_ACCESS. I followed instructions here and other places on how to use NSZombieEnabled to identify prematurely released objects but this one comes without any helpful msgs even with NSZombieEnabled. My guess is it must be caused by something trying to access unassigned memory that wasn't released through release/autorelease. Or else it would have been picked up as zombie object like the other errors I have been able to fix. I'm not a c expert but does that mean something like that could happen if I were to declare an object and send it a message without ever instantiating it? I looked through my code to see if I had anything like that and I came up empty. I have the stack trace in the debugger for this but I'm not sure how to make use of it. I'm a little frustrated because I can't use breakpoints in the code to narrow down the problem any further since it seems to happen after the app has finished loading. I thought the app would just stay idle if there was no possible user interaction. Is it failing at the tail end of the load where I can't easy see it or is jut doing stuff in the background after it's done loading. And I would much appreciate any tips on how to read the stacktrace for this. Thanks for the help guys.

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  • STLport crash (race condition, Darwin only?)

    - by Jonas Byström
    When I run STLport on Darwin I get a strange crash. (Haven't seen it anywhere else than on Mac, but exactly same thing crash on both i686 and PowerPC.) This is what it looks like in gdb: Program received signal EXC_BAD_ACCESS, Could not access memory. Reason: 13 at address: 0x0000000000000000 [Switching to process 21097] 0x000000010120f47c in stlp_std::__node_alloc_impl::_M_allocate () It may be some setting in STLport, I noticed that Mac.h and MacOSX.h seemed far behind on features. I also know that it it must be some type of race condition, since it doesn't occur just by calling this method (implicity called). The crash happens mainly when I push the system, running 10 simultaneous threads that do a lot of string handling. Other theories I come up with have to do with compiler flags (configure script) and g++ 4.2 bugs (seems like 4.4.3 isn't on Mac yet with Objective-C support, which I need to link with). HELP!!! :) Edit: I run unit tests, which do all sorts of things. This problem arise when I start 10 threads that push the system; and it always comes down to std::string::append which eventually boils down to _M_allocate. Since I can't even get a descent dump of the code that's causing the problem, I figure I'm doing something bad. Could it be so since it's trying to execute at instruction pointer 0x000...000? Are dynlibs built as DLLs in Windows with a jump table? Could it perhaps be that such a jump table has been overwritten for some reason? That would probably explain this behavior. (The code is huge, if I run out of other ideas, I'll post a minimum crashing sample here.)

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  • PHP Multiple Calls to Server Share Objects?

    - by user1513171
    I’m wondering this about PHP on Apache. Do multiple calls to the server from different users—could be sitting next to each other, in different states, different countries, etc…—share memory? For example, if I create a static variable in a PHP script and set it to 1 by default, then user1 comes in and it changes to 2, and then almost at the exactly same time, user2 comes in, does he see that static variable with a value of 1 or 2? An even better example is this class I have in PHP: class ApplicationRegistry { private static $instance; private static $PDO; private function __construct() { self::$PDO = $db = new \PDO('mysql:unix_socket=/........'); self::$PDO->setAttribute(\PDO::ATTR_ERRMODE, \PDO::ERRMODE_EXCEPTION); } static function instance() { if(!isset(self::$instance)) { self::$instance = new self(); } return self::$instance; } static function getDSN() { if(!isset(self::$PDO)) { self::instance(); return self::$PDO; } return self::$PDO; } } So this is a Singleton that has a static PDO instance. If user1 and user2 are hitting the server at the exact same time are they using different instances of PDO or are they using the same one? This is a confusing concept for me and I'm trying to think of how my application will scale.

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  • when long polling, Why are my other requests taking so long?

    - by Pascal
    The client makes 2 concurrent requests. (1 which takes 60 seconds - long polling) and another which is NOT long polling - supposed to return right away. It does return right away when I'm not doing long polling. But as soon as I start doing long polling with the other thread, the other one takes forever to execute. Firebug shows that the request is waiting for 10-50 seconds. On the server, I profiled ALL requests from the moment the php script starts to the time it goes back to the client, and it shows that each one only took 300ms or less. This problem started about the same time I started doing long polling (with the other XHR requests). I'm using jquery for both requests. The server shows that it is under very light load. CPU and memory less then 2%. 8 processes running out of a pool of 15. (it doesn't seem to deviate much from that number 8, even when I run more ajax requests). I guess each process can run multiple ajax threads concurrently. I made sure to EXIT from all processes as soon as their done executing. I don't see how the process pool has run out, if there are still 7 unused processes listed under prstat -J. Also, the problem happens somewhat intermittently. Firefox should be able to handle 2 concurrent ajax requests. i dont get what the problem is.

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  • Using graphical ActiveX (COM) controls in WinForms project

    - by alex
    I have a collection (set) of ActiveX controls. I recieved them from our vendor company. I created a wrappers for them using tlbimp.exe and aximp.exe. All non-graphical controls work good. All graphical controls don't react on some methods. When I call their methods I get: TargetInvocativeException (InnerException is null). or Attempt to read/write protected memory. Our vendor company assure that their graphical activex controls work good. But they don't provide support service, so I have to find solution of my problem alone. And some more, All graphical activex controls don't react on mouseclick or any other mouse manipulations. But documentation says: it must change the color on mouse click. Maybe, someone have same symptoms and can help me ! I googled over that problem many pages but they don't help me. Maybe it's some Visual Studio settings or compiler options ? I use VS 2005.

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  • Learning about the low level

    - by Anoners
    I'm interested in learning more about the PC from a lower (machine) level. I graduated from a school which taught us concepts using the Java language which abstracted out that level almost completely. As a result I only learned a bit from the one required assembly language course. In order to cram in ASM and quite a few details about architecture, it was hard to get a very deep picture of what is going on there. At work I focus on unix socket programming in C, so i'm much closer to the hardware now, but I feel I should learn a bit more about what streams really are, how memory management and paging works, what goes on when you call "paint()" on a graphics buffer, etc. I missed out on a lot of this and i'm looking for a good resource to get me started. I've heard a lot about the "Pink Book" by Peter Norton (Programmer's Guide to the IBM PC, Programmer's Guide to inside the PC, etc). It seems like this is on the right track, however the original is quite out dated and the newer ones have had conflicting reviews, with many people saying to stay away from it. I'm not sure what the SO crowd thinks about this book or if they have some suggestions for similar books, online resources, etc that may be good primers for this sort of thing. Any suggestions would be appreciated.

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  • Why does perl crash with "*** glibc detected *** perl: munmap_chunk(): invalid pointer"?

    - by sid_com
    #!/usr/bin/env perl use warnings; use strict; use 5.012; use XML::LibXML::Reader; my $reader = XML::LibXML::Reader->new( location => 'http://www.heise.de/' ) or die $!; while ( $reader->read ) { say $reader->name; } At the end of the output from this script I get this error-messages: * glibc detected * perl: munmap_chunk(): invalid pointer: 0x0000000000b362e0 * ======= Backtrace: ========= /lib64/libc.so.6[0x7fb84952fc76] ... ======= Memory map: ======== 00400000-0053d000 r-xp 00000000 08:01 182002 /usr/local/bin/perl ... Is this due a bug? perl -V: Summary of my perl5 (revision 5 version 12 subversion 0) configuration: Platform: osname=linux, osvers=2.6.31.12-0.2-desktop, archname=x86_64-linux uname='linux linux1 2.6.31.12-0.2-desktop #1 smp preempt 2010-03-16 21:25:39 +0100 x86_64 x86_64 x86_64 gnulinux ' config_args='-Dnoextensions=ODBM_File' hint=recommended, useposix=true, d_sigaction=define useithreads=undef, usemultiplicity=undef useperlio=define, d_sfio=undef, uselargefiles=define, usesocks=undef use64bitint=define, use64bitall=define, uselongdouble=undef usemymalloc=n, bincompat5005=undef Compiler: cc='cc', ccflags ='-fno-strict-aliasing -pipe -fstack-protector -I/usr/local/include -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64', optimize='-O2', cppflags='-fno-strict-aliasing -pipe -fstack-protector -I/usr/local/include' ccversion='', gccversion='4.4.1 [gcc-4_4-branch revision 150839]', gccosandvers='' intsize=4, longsize=8, ptrsize=8, doublesize=8, byteorder=12345678 d_longlong=define, longlongsize=8, d_longdbl=define, longdblsize=16 ivtype='long', ivsize=8, nvtype='double', nvsize=8, Off_t='off_t', lseeksize=8 alignbytes=8, prototype=define Linker and Libraries: ld='cc', ldflags =' -fstack-protector -L/usr/local/lib' libpth=/usr/local/lib /lib /usr/lib /lib64 /usr/lib64 /usr/local/lib64 libs=-lnsl -ldl -lm -lcrypt -lutil -lc perllibs=-lnsl -ldl -lm -lcrypt -lutil -lc libc=/lib/libc-2.10.1.so, so=so, useshrplib=false, libperl=libperl.a gnulibc_version='2.10.1' Dynamic Linking: dlsrc=dl_dlopen.xs, dlext=so, d_dlsymun=undef, ccdlflags='-Wl,-E' cccdlflags='-fPIC', lddlflags='-shared -O2 -L/usr/local/lib -fstack-protector' Characteristics of this binary (from libperl): Compile-time options: PERL_DONT_CREATE_GVSV PERL_MALLOC_WRAP USE_64_BIT_ALL USE_64_BIT_INT USE_LARGE_FILES USE_PERLIO USE_PERL_ATOF Built under linux Compiled at Apr 15 2010 13:25:46 @INC: /usr/local/lib/perl5/site_perl/5.12.0/x86_64-linux /usr/local/lib/perl5/site_perl/5.12.0 /usr/local/lib/perl5/5.12.0/x86_64-linux /usr/local/lib/perl5/5.12.0 .

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  • Hibernate: order multiple one-to-many relations

    - by Markos Fragkakis
    I have a search screen, using JSF, JBoss Seam and Hibernate underneath. There are columns for A, B and C, where the relations are as follows: A (1< -- ) B (1< -- ) C A has a List< B and B has a List< C (both relations are one-to-many). The UI table supports ordering by any column (ASC or DESC), so I want the results of the query to be ordered. This is the reason I used Lists in the model. However, I got an exception that Hibernate cannot eagerly fetch multiple bags (it considers both lists to be bags). There is an interesting blog post here, and they identify the following solutions: Use @IndexColumn annotation (there is none in my DB, and what's more, I want the position of results to be determined by the ordering, not by an index column) Fetch lazily (for performance reasons, I need eager fetching) Change List to Set So, I changed the List to Set, which by the way is more correct, model-wise. First, if don't use @OrderBy, the PersistentSet returned by Hibernate wraps a HashSet, which has no ordering. Second, If I do use @OrderBy, the PersistentSet wraps a LinkedHashSet, which is what I would like, but the OrderBy property is hardcoded, so all other ordering I perform through the UI comes after it. I tried again with Sets, and used SortedSet (and its implementation, TreeSet), but I have some issues: I want ordering to take place in the DB, and not in-memory, which is what TreeSet does (either through a Comparator, or through the Comparable interface of the elements). Second, I found that there is the Hibernate annotation @Sort, which has a SortOrder.UNSORTED and you can also set a Comparator. I still haven't managed to make it compile, but I am still not convinced it is what I need. Any advice?

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  • Using StringBuilder to process csv files to save heap space

    - by portoalet
    I am reading a csv file that has about has about 50,000 lines and 1.1MiB in size (and can grow larger). In Code1, I use String to process the csv, while in Code2 I use StringBuilder (only one thread executes the code, so no concurrency issues) Using StringBuilder makes the code a little bit harder to read that using normal String class. Am I prematurely optimizing things with StringBuilder in Code2 to save a bit of heap space and memory? Code1 fr = new FileReader(file); BufferedReader reader = new BufferedReader(fr); String line = reader.readLine(); while ( line != null ) { int separator = line.indexOf(','); String symbol = line.substring(0, seperator); int begin = separator; separator = line.indexOf(',', begin+1); String price = line.substring(begin+1, seperator); // Publish this update publisher.publishQuote(symbol, price); // Read the next line of fake update data line = reader.readLine(); } Code2 fr = new FileReader(file); StringBuilder stringBuilder = new StringBuilder(reader.readLine()); while( stringBuilder.toString() != null ) { int separator = stringBuilder.toString().indexOf(','); String symbol = stringBuilder.toString().substring(0, separator); int begin = separator; separator = stringBuilder.toString().indexOf(',', begin+1); String price = stringBuilder.toString().substring(begin+1, separator); publisher.publishQuote(symbol, price); stringBuilder.replace(0, stringBuilder.length(), reader.readLine()); }

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  • Mapping issue with multi-field primary keys using hibernate/JPA annotations

    - by Derek Clarkson
    Hi all, I'm stuck with a database which is using multi-field primary keys. I have a situation where I have a master and details table, where the details table's primary key contains fields which are also the foreign key's the the master table. Like this: Master primary key fields: master_pk_1 Details primary key fields: master_pk_1 details_pk_2 details_pk_3 In the Master class we define the hibernate/JPA annotations like this: @Id @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "idGenerator") @Column(name = "master_pk_1") private long masterPk1; @OneToMany(cascade=CascadeType.ALL) @JoinColumn(name = "master_pk_1", referencedColumnName = "master_pk_1") private List<Details> details = new ArrayList<Details>(); And in the details class I have defined the id and back reference like this: @EmbeddedId @AttributeOverrides( { @AttributeOverride( name = "masterPk1", column = @Column(name = "master_pk_1")), @AttributeOverride(name = "detailsPk2", column = @Column(name = "details_pk_2")), @AttributeOverride(name = "detailsPk2", column = @Column(name = "details_pk_2")) }) private DetailsPrimaryKey detailsPrimaryKey = new DetailsPrimaryKey(); @ManyToOne @JoinColumn(name = "master_pk_1", referencedColumnName = "master_pk_1", insertable=false) private Master master; The goal of all of this was that I could create a new master, add some details to it, and when saved, JPA/Hibernate would generate the new id for master in the masterPk1 field, and automatically pass it down to the details records, storing it in the matching masterPk1 field in the DetailsPrimaryKey class. At least that's what the documentation I've been looking at implies. What actually happens is that hibernate appears to corectly create and update the records in the database, but not pass the key to the details classes in memory. Instead I have to manually set it myself. I also found that without the insertable=true added to the back reference to master, that hibernate would create sql that had the master_pk_1 field listed twice in the insert statement, resulting in the database throwing an exception. My question is simply is this arrangement of annotations correct? or is there a better way of doing it?

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  • Long running stateful service in .NET

    - by Asaf R
    Hi, I need to create a service in .NET that maintains (inner) state in-memory, spawns multiple threads and is generally long-running. There are a lot options - Good-old Windows Service Windows Communication Services Windows Workflow Foundation I really don't know which to choose. Most of the functionality is in a library used by this service, so the service itself is rather simple. On one hand, it's important the service host is as close to "simply working" as possible, which excludes Windows Service. On the other hand, it's important that the service is not taken down by the host just because there's no external activity, which makes WCF kind o' "scary". As for WF, it's strongest selling point is the ability to create processes as, um..., workflows, which is something I don't need nor want. To sum it up, the plethora of Microsoft technologies got me a bit confused. I'd appreciate help regarding the pros and cons of each solution (or other's I've failed to mention) for the problem of a stateful, long running service in .NET Thanks, Asaf P.S., I'm using .NET 4. EDIT: What I mean by the host "simply working" is, for example, that the service I create be reactivated if it crashes. I guess the reason for this question is that I've created Windows Services in the past (I think it was in plain C++ with Win32 API), and I don't want to miss out on something simpler if there's is such as thing. Thanks for all the replies thus far! Asaf.

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  • What are the primitive Forth operators?

    - by Barry Brown
    I'm interested in implementing a Forth system, just so I can get some experience building a simple VM and runtime. When starting in Forth, one typically learns about the stack and its operators (DROP, DUP, SWAP, etc.) first, so it's natural to think of these as being among the primitive operators. But they're not. Each of them can be broken down into operators that directly manipulate memory and the stack pointers. Later one learns about store (!) and fetch (@) which can be used to implement DUP, SWAP, and so forth (ha!). So what are the primitive operators? Which ones must be implemented directly in the runtime environment from which all others can be built? I'm not interested in high-performance; I want something that I (and others) can learn from. Operator optimization can come later. (Yes, I'm aware that I can start with a Turing machine and go from there. That's a bit extreme.) Edit: What I'm aiming for is akin to bootstrapping an operating system or a new compiler. What do I need do implement, at minimum, so that I can construct the rest of the system out of those primitive building blocks? I won't implement this on bare hardware; as an educational exercise, I'd write my own minimal VM.

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  • iPhone app stopped building crash reports

    - by BankStrong
    My app formerly created useful crash logs. I synced my iPhone in the past and found crash logs in library/logs/CrashReporter About a month ago, my app stopped creating crash reports. When I first discovered this problem, I assumed it was due to memory corruption (a possibility in my app). I just created a new project and added a crash to it. // Implement viewDidLoad to do additional setup after loading the view, // typically from a nib. - (void)viewDidLoad { NSMutableArray *array = [[NSMutableArray alloc] init]; [array removeObjectAtIndex:-1]; [super viewDidLoad]; } This app does not create a crash report either. Ideas I've started to explore: My phone is corrupted (tried restoring - somehow I brought it to the state from a few months ago) My XCode is corrupt (tried reinstalling, but current download demands Snow Leopard - and I can't upgrade to Snow Leopard online). This seems possible - I may have messed with device support around a month ago (similar to http://stackoverflow.com/questions/1224867/does-iphone-os-3-0-1-ruin-your-development-phone ) The location for crash logs has somehow moved. Suggestions?

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  • Why calling Process.killProcess(Process.myPid()) is a bad idea?

    - by Tal Kanel
    I've read some posts saying using this method is "not good", shouldn't been use, it's not the right way to "close" the application and it's not how android works... I understand and accept the fact that Android OS knows better then me when it's the right time to terminate the process, but I didn't heard yet a good explanation why it's wrong using the killProcess() method?. after all - it's part of the android API... what I do know is that calling this method while other threads doing in potential an important work (operations on files, writing to DB, HTTP requests, running services..) can be terminated in the middle, and it's clearly not good. also I know I can benefit from the fact that "re-open" the application will be faster, cause the system maybe still "holds" in memory state from last time been used, and killProcess() prevents that. beside this reason, in assumption I don't have such operations, and I don't care my application will load from scratch each run, there are other reasons why not using the killProcess() method? I know about finish() method to close an Activity, so don't write me about that please.. finish() is only for Activity. not to all application, and I think I know exactly why and when to use it... and another thing - I'm developing also games with the Unity3D framework, and exporting the project to android. when I decompiled the generated apk, I was very suprised to find out that the java source code created from unity - implementing Unity's - Application.quit() method, with Process.killProcess(Process.myPid()). Application.quit() is suppose to be the right way to close game according to Unity3d guides (is it really?? maybe I'm wrong, and missed something), so how it happens that the Unity's framework developers which doing a very good work as it seems implemented this in native android to killProcess()? anyway - I wish to have a "list of reasons" why not using the killProcess() method, so please write down your answer - if you have something interesting to say about that. TIA

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  • Unknown Exception on trying to initialize the web service stub created by Axis C++

    - by Harsha Reddy
    Hi, I am trying out the sample calculator program given in the folder of axis c++. I am mainly interested in the client side. So I used the wsdl to create the stubs and my main is pretty much the same as given in the sample. However on executing the call Calculator ws (endpoint) I get an unknown exception "First-chance exception at 0x7c0024b9 in CalculatorClient.exe: 0xC0000005: Access violation reading location 0x00000000. First-chance exception at 0x7c812afb in CalculatorClient.exe: Microsoft C++ exception: [rethrow] at memory location 0x00000000.. Unhandled exception at 0x7c0024b9 in CalculatorClient.exe: 0xC0000005: Access violation reading location 0x00000000." and the exception causing code is Calculator::Calculator(const char* pchEndpointUri, AXIS_PROTOCOL_TYPE eProtocol) :Stub(pchEndpointUri, eProtocol) { } I had earlier tried to run a a webservice using Axis C++ but had received the same error. At that time my web service was a java ws on WAS. Then I later tried the calculator client (but this time I did not have any server hosting the ws as I just wanted to check if the Client could initialize). Is the problem caused due to the web service not being hosted on Apache in C++ (though I highly doubt it). Any help would be appreciated. Thanks, Harsha

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