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  • core dump during std::_List_node_base::unhook()

    - by Ron
    I have a program where std::list is used. The program uses threads which act on the std::list as producers and consumers. When a message is dealt with by the consumer, it is removed from the list using pop_front(). But, during pop_front, there is a core dump. The gdb trace is as below. could you help getting me some insights into this issue? (gdb) bt full 0 0xf7531d7b in std::_List_node_base::unhook () from /usr/lib/libstdc++.so.6 No symbol table info available. 1 0x0805c600 in std::list ::_M_erase (this=0x806b08c, __position={_M_node = 0x8075308}) at /opt/target/usr/include/c++/4.2.0/bits/stl_list.h:1169 __n = (class std::_List_node<myMsg> *) 0x0 2 0x0805c6af in std::list ::pop_front (this=0x806b08c) at /opt/target/usr/include/c++/4.2.0/bits/stl_list.h:750 No locals. 3 0x0805afb6 in Base::run () at ../../src/Base.cc:342 nSentBytes = 130 tmpnm = {_vptr.myMsg = 0x80652c0, m_msg = 0x8075140 "{0130,MSG_TYPE=ND_FUNCTION,ORG_PNAME=P01vm01Ax,FUNCTION=LOG,PARAM_CNT=3,DATETIME=06/12/2010 02:59:26.187,LOGNAME=N,ENTRY=Debug 0 }", m_from = 0x8096ee0 "P01vm01Ax", m_to = 0x0, static m_logged = false, static m_pLogMutex = {_data = {_lock = 0, __count = 0, __owner = 0, __kind = 0, _nusers = 0, {_spins = 0, _list = {_next = 0x0}}}, __size = '\0' , __align = 0}} newMsg = {_vptr.myMsg = 0x80652c0, m_msg = 0x0, m_from = 0x0, m_to = 0x0, static m_logged = false, static m_pLogMutex = {_data = {_lock = 0, __count = 0, __owner = 0, __kind = 0, _nusers = 0, {_spins = 0, _list = {_next = 0x0}}}, __size = '\0' , __align = 0}} strBuffer = "{0440,MSG_TYPE=NG_FUNCTION,ORG_PNAME=mach01./opt/abc/VAvsk/abc/comp/DML/gendrs.pl.17560,DST_PNAME=P01vm01Ax,FUNCTION=DRS_REPLICATE,CAUSE_DML_ERROR=N,CORRUPT_DATA=N,CORRUPT_HEADER=N,DEBUG=Y,EXTENDED_RU"... fds = {{fd = 5, events = 1, revents = 0}} retval = 0 iWaitTime = 0 4 0x0805b277 in startRun () at ../../src/Base.cc:454 No locals. 5 0xf7effe7b in start_thread () from /lib/libpthread.so.0 No symbol table info available. 6 0xf744d82e in clone () from /lib/libc.so.6 No symbol table info available.

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  • Fixing a multi-threaded pycurl crash.

    - by Rook
    If I run pycurl in a single thread everything works great. If I run pycurl in 2 threads python will access violate. The first thing I did was report the problem to pycurl, but the project died about 3 years ago so I'm not holding my breath. My (hackish) solution is to build a 2nd version of pycurl called "pycurl_thread" which will only be used by the 2nd thread. I downloaded the pycurl module from sourceforge and I made a total of 4 line changes. But python is still crashing. My guess is that even though this is a module with a different name (import pycurl_thread), its still sharing memory with the original module (import pycurl). How should I solve this problem? Changes in pycurl.c: initpycurl(void) to initpycurl_thread(void) and m = Py_InitModule3("pycurl", curl_methods, module_doc); to m = Py_InitModule3("pycurl_thread", curl_methods, module_doc); Changes in setup.py: PACKAGE = "pycurl" PY_PACKAGE = "curl" to PACKAGE = "pycurl_thread" PY_PACKAGE = "curl_thread" Here is the seg fault i'm getting. This is happening within the C function do_curl_perform(). *** longjmp causes uninitialized stack frame ***: python2.7 terminated ======= Backtrace: ========= /lib/libc.so.6(__fortify_fail+0x37)[0x7f209421b537] /lib/libc.so.6(+0xff4c9)[0x7f209421b4c9] /lib/libc.so.6(__longjmp_chk+0x33)[0x7f209421b433] /usr/lib/libcurl.so.4(+0xe3a5)[0x7f20931da3a5] /lib/libpthread.so.0(+0xfb40)[0x7f209532eb40] /lib/libc.so.6(__poll+0x53)[0x7f20941f6203] /usr/lib/libcurl.so.4(Curl_socket_ready+0x116)[0x7f2093208876] /usr/lib/libcurl.so.4(+0x2faec)[0x7f20931fbaec] /usr/local/lib/python2.7/dist-packages/pycurl.so(+0x892b)[0x7f209342c92b] python2.7(PyEval_EvalFrameEx+0x58a1)[0x4adf81] python2.7(PyEval_EvalCodeEx+0x891)[0x4af7c1] python2.7(PyEval_EvalFrameEx+0x538b)[0x4ada6b] python2.7(PyEval_EvalFrameEx+0x65f9)[0x4aecd9]

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  • DB2 Driver Connection Hanging in Glassfish Connection Pool

    - by Ant
    We have an intermittent issue around the DB2 used from a Glassfish connection pool. What happens is this: Under situations where the database (DB2 on ZOS) is under stress, our application (which is a multi-threaded application using connections to DB2 via a Glassfish connection pool) stops doing anything. The following are observed: 1) Looking at the server using JConsole, we can see a thread waiting indefinitely in the DB2 driver's getConnection() method. We can also see that it has gained a lock on a Vector within the driver. Several other threads are also calling the getConnection() method in the driver, and are hanging waiting for the lock on the Vector to be released. 2) Looking at the database itself, we can see that there are connections from the Glassfish server open and waiting to be used. It seems that there is some sort of mismatch between the connection pool on Glassfish and the connections actually open to DB2. Has anyone come across this issue before? Or something similar? If you need any more information that I haven't provided, then please let me know!

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  • FILE* issue PPU side code

    - by Cristina
    We are working on a homework on CELL programming for college and their feedback response to our questions is kinda slow, thought i can get some faster answers here. I have a PPU side code which tries to open a file passed down through char* argv[], however this doesn't work it cannot make the assignment of the pointer, i get a NULL. Now my first idea was that the file isn't in the correct directory and i copied in every possible and logical place, my second idea is that maybe the PPU wants this pointer in its LS area, but i can't deduce if that's the bug or not. So... My question is what am i doing wrong? I am working with a Fedora 7 SDK Cell, with Eclipse as an IDE. Maybe my argument setup is wrong tho he gets the name of the file correctly. Code on request: images_t *read_bin_data(char *name) { FILE *file; images_t *img; uint32_t *buffer; uint8_t buf; unsigned long fileLen; unsigned long i; //Open file file = (FILE*)malloc(sizeof(FILE)); file = fopen(name, "rb"); printf("[Debug]Opening file %s\n",name); if (!file) { fprintf(stderr, "Unable to open file %s", name); return NULL; } //....... } Main launch: int main(int argc,char* argv[]) { int i,img_width; int modif_this[4] __attribute__ ((aligned(16))) = {1,2,3,4}; images_t *faces, *nonfaces; spe_context_ptr_t ctxs[SPU_THREADS]; pthread_t threads[SPU_THREADS]; thread_arg_t arg[SPU_THREADS]; //intializare img_width img_width = atoi(argv[1]); printf("[Debug]Img size is %i\n",img_width); faces = read_bin_data(argv[3]); //....... } Thanks for the help.

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  • Atomic int writes on file

    - by Waneck
    Hello! I'm writing an application that will have to be able to handle many concurrent accesses to it, either by threads as by processes. So no mutex'es or locks should be applied to this. To make the use of locks go down to a minimum, I'm designing for the file to be "append-only", so all data is first appended to disk, and then the address pointing to the info it has updated, is changed to refer to the new one. So I will need to implement a small lock system only to change this one int so it refers to the new address. How is the best way to do it? I was thinking about maybe putting a flag before the address, that when it's set, the readers will use a spin lock until it's released. But I'm afraid that it isn't at all atomic, is it? e.g. a reader reads the flag, and it is unset on the same time, a writer writes the flag and changes the value of the int the reader may read an inconsistent value! I'm looking for locking techniques but all I find is either for thread locking techniques, or to lock an entire file, not fields. Is it not possible to do this? How do append-only databases handle this? Thanks! Cauê

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  • Sell me Distributed revision control

    - by ring bearer
    I know 1000s of similar topics floating around. I read at lest 5 threads here in SO But why am I still not convinced about DVCS? I have only following questions (note that I am selfishly worried only about Java projects) What is the advantage or value of committing locally? What? really? All modern IDEs allows you to keep track of your changes? and if required you can restore a particular change. Also, they have a feature to label your changes/versions at IDE level!? what if I crash my hard drive? where did my local repository go? (so how is it cool compared to checking in to a central repo?) Working offline or in an air plane. What is the big deal?In order for me to build a release with my changes, I must eventually connect to the central repository. Till then it does not matter how I track my changes locally. Ok Linus Torvalds gives his life to Git and hates everything else. Is that enough to blindly sing praises? Linus lives in a different world compared to offshore developers in my mid-sized project? Pitch me!

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  • Message queue proxy in Python + Twisted

    - by gasper_k
    Hi, I want to implement a lightweight Message Queue proxy. It's job is to receive messages from a web application (PHP) and send them to the Message Queue server asynchronously. The reason for this proxy is that the MQ isn't always avaliable and is sometimes lagging, or even down, but I want to make sure the messages are delivered, and the web application returns immediately. So, PHP would send the message to the MQ proxy running on the same host. That proxy would save the messages to SQLite for persistence, in case of crashes. At the same time it would send the messages from SQLite to the MQ in batches when the connection is available, and delete them from SQLite. Now, the way I understand, there are these components in this service: message listener (listens to the messages from PHP and writes them to a Incoming Queue) DB flusher (reads messages from the Incoming Queue and saves them to a database; due to SQLite single-threadedness) MQ connection handler (keeps the connection to the MQ server online by reconnecting) message sender (collects messages from SQlite db and sends them to the MQ server, then removes them from db) I was thinking of using Twisted for #1 (TCPServer), but I'm having problem with integrating it with other points, which aren't event-driven. Intuition tells me that each of these points should be running in a separate thread, because all are IO-bound and independent of each other, but I could easily put them in a single thread. Even though, I couldn't find any good and clear (to me) examples on how to implement this worker thread aside of Twisted's main loop. The example I've started with is the chatserver.py, which uses service.Application and internet.TCPServer objects. If I start my own thread prior to creating TCPServer service, it runs a few times, but the it stops and never runs again. I'm not sure, why this is happening, but it's probably because I don't use threads with Twisted correctly. Any suggestions on how to implement a separate worker thread and keep Twisted? Do you have any alternative architectures in mind?

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  • bad_alloc occuring when allocating small structs

    - by SalamiArmi
    A bad_alloc has started showing up in some code which looks perfectly valid to me and has worked very well in the past. The bad alloc only occurs once every 50-3000 iterations of the code, which is also confusing. The code itself is from a singly linked list, simply adding a new element to the queue: template<typename T> struct container { inline container() : next(0) {} container *next; T data; }; void push(const T &data) { container<T> *newQueueMember = new container<T>; //... unrelated to crash } Where T is: struct test { int m[256]; }; Changing the size of the array allocated array to anything but very small values (1-8 ints) still results in a bad_alloc occasionally. A few extra notes about my program: - I used Poco::ThreadPool to thread my program. I've only recently added this functionality, before I had it running with Win32 threads. However, only the main thread ever calls push(). - I am also occasionally getting other crashes which could be related. However, when I try to debug with visual studio 2008, I can't navigate back to the call stack, or the crash happens deep within new(). Thanks in advance.

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  • How do I update a progress bar in Cocoa during a long running loop?

    - by Nic
    Hi, I've got a while loop, that runs for many seconds and that's why I want to update a progress bar (NSProgressIndicator) during that process, but it updates only once after the loop has finished. The same happens if I want to update a label text, by the way. I believe, my loop prevents other things of that application to happen. There must be another technique. Does this have to do with threads or something? Am I on the right track? Can someone please give me a simple example, how to “optimize” my application? My application is a Cocoa Application (Xcode 3.2.1) with these two methods in my Example_AppDelegate.m: // This method runs when a start button is clicked. - (IBAction)startIt:(id)sender { [progressbar setDoubleValue:0.0]; [progressbar startAnimation:sender]; running = YES; // this is a instance variable int i = 0; while (running) { if (i++ = processAmount) { // processAmount is something like 1000000 running = NO; continue; } // Update progress bar double progr = (double)i / (double)processAmount; NSLog(@"progr: %f", progr); // Logs values between 0.0 and 1.0 [progressbar setDoubleValue:progr]; [progressbar needsDisplay]; // Do I need this? // Do some more hard work here... } } // This method runs when a stop button is clicked, but as long // as -startIt is busy, a click on the stop button does nothing. - (IBAction)stopIt:(id)sender { NSLog(@"Stop it!"); running = NO; [progressbar stopAnimation:sender]; } I'm really new to Objective-C, Cocoa and applications with a UI. Thank you very much for any helpful answer.

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  • Are mathematical Algorithms protected by copyright?

    - by analogy
    I wish to implement an algorithm which i read in a journal paper in my software (commercial). I want to know if this is allowed or not. The algorithm in question is described in http://arxiv.org/abs/0709.2938 It is a very simple algorithm and a number of implementations exist in python (http://igraph.sourceforge.net/) and java. One of them is in gpl another which i got from a different researcher and had no license attached. There are significant differences in two implementations, e.g. second one uses threads and multiple cores. It is possible to rewrite/ (not translate) the algorithm. So can I use it in my software or on a server for commercial purpose. Thanks UPDATE: I am completely aware of copyright on the text of paper, it was published in phys rev E. I am concerned with use of the algorithm, in commercial software. Also the publication means that unless the patent has been already filed. The method has been disclosed publicly hence barring patent in future. Also the GPL implementation is not by authors themselves but comes from a third party. Finally i am not using the GPL implementation but creating my own using C++.

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  • Devise routes to only use custom sign in page

    - by eblume
    I am trying to learn Devise and seem to have hit a problem that is nearly the same as many, many questions here on SO but just slightly different enough that I am not getting much traction following those questions' threads. I have a very simple application. Users can sign in and sign out (and also the devise 'forgot password' stuff is enabled - I am not concerned about it at this time) and that is it. They can't register, they can't edit their profile other than to change their password, they can't do anything except sign in and sign out. (Account creation will, for now, be handled manually at the command line.) I would vastly prefer that the only page that users can log in from was "/" (root_path). I already have it working where you can log in from "/", and that is great. The problem I am having is that if you type in your user/password combination incorrectly from the root_path login page, it automatically sends you to the Devise sign-in page to continue trying to sign in. How can I make Devise redirect to root_path on sign-in failure? Here are my routes - they are probably not optimal or correctly configured and I would appreciate pointers on fixing them: root to: "core_pages#splash" devise_for :users, skip: [:sessions] as :user do # get 'signin' => 'devise/sessions#new', as: :new_user_session post 'signin' => 'devise/sessions#create', as: :user_session delete 'signout' => 'devise/sessions#destroy', as: :destroy_user_session, via: Devise.mappings[:user].sign_out_via end match '/home' => 'core_pages#home' Note the commented-out 'get signin' line. The system works without this line but, surprisingly (to me), "GET /signin" results in a HTTP 400 (OK) response and renders the Devise login template. I would prefer it return some sort of 'invalid request' or just silently redirect the user to root_path. Running rake routes on these routes gives: root / core_pages#splash user_password POST /users/password(.:format) devise/passwords#create new_user_password GET /users/password/new(.:format) devise/passwords#new edit_user_password GET /users/password/edit(.:format) devise/passwords#edit PUT /users/password(.:format) devise/passwords#update user_session POST /signin(.:format) devise/sessions#create destroy_user_session DELETE /signout(.:format) devise/sessions#destroy home /home(.:format) core_pages#home Thanks!

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  • Replace low level web-service reference call transport with custom one

    - by hoodoos
    I'm not sure if title sounds right actually, so I will give more explanation here. I will begin from very beginning :) I'm using c# and .net for my development. I have an application that makes requests to some soap web-service and for each user request it produces 3 to 10 requests for web-service, they should all run async to finish in one time, so I use Async method of the web-service generated reference and then wait for result on callback. But it seems like it starts a thread (or takes it from pool) for every async call I make, so if I have 10 clients I got to spawn 30 to 100 threads and it sounds terrible even for my 16 cores server :) So i wanted to replace low level transport implementation with my own which uses non-blocking sockets and can handle at least 50 sockets run parallel in one thread with not much overhead. But I actually dunno where to put my override best. I analyzed System.Web.Services.Protocols.SoapHttpClientProtocol class and see that it has some GetWebRequest method which I actually could use. If only I could somehow interupt the object it creates and get a http request with all headers and body from there and then send it with my own sockets.. Any ideas what approach to use? Or maybe there's something built in the framework I can use?

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  • Should a new language compiler target the JVM?

    - by Pindatjuh
    I'm developing a new language. My initial target was to compile to native x86 for the Windows platform, but now I am in doubt. I've seen some new languages target the JVM (most notable Scala and Clojure). Ofcourse it's not possible to port every language easily to the JVM; to do so, it may lead to small changes to the language and it's design. So that's the reason behind this doubt, and thus this question: Is targetting the JVM a good idea, when creating a compiler for a new language? Or should I stick with x86? I have experience in generating JVM bytecode. Are there any workarounds to JVM's GC? The language has deterministic implicit memory management. How to produce JIT-compatible bytecode, such that it will get the highest speedup? Is it similar to compiling for IA-32, such as the 4-1-1 muops pattern on Pentium? I can imagine some advantages (please correct me if I'm wrong): JVM bytecode is easier than x86. Like x86 communicates with Windows, JVM communicates with the Java Foundation Classes. To provide I/O, Threading, GUI, etc. Implementing "lightweight"-threads.I've seen a very clever implementation of this at http://www.malhar.net/sriram/kilim/. Most advantages of the Java Runtime (portability, etc.) The disadvantages, as I imagined, are: Less freedom? On x86 it'll be more easy to create low-level constructs, while JVM has a higher level (more abstract) processor. Most disadvantages of the Java Runtime (no native dynamic typing, etc.)

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  • How does the socket API accept() function work?

    - by Eli Bendersky
    The socket API is the de-facto standard for TCP/IP and UDP/IP communications (that is, networking code as we know it). However, one of its core functions, accept() is a bit magical. To borrow a semi-formal definition: accept() is used on the server side. It accepts a received incoming attempt to create a new TCP connection from the remote client, and creates a new socket associated with the socket address pair of this connection. In other words, accept returns a new socket through which the server can communicate with the newly connected client. The old socket (on which accept was called) stays open, on the same port, listening for new connections. How does accept work? How is it implemented? There's a lot of confusion on this topic. Many people claim accept opens a new port and you communicate with the client through it. But this obviously isn't true, as no new port is opened. You actually can communicate through the same port with different clients, but how? When several threads call recv on the same port, how does the data know where to go? I guess it's something along the lines of the client's address being associated with a socket descriptor, and whenever data comes through recv it's routed to the correct socket, but I'm not sure. It'd be great to get a thorough explanation of the inner-workings of this mechanism.

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  • c multithreading

    - by coubeatczech
    hi, there's a weird behaviour in my threads: void * foo(void * nic){ printf("foo"); } void * threadF(void * ukazatel){ printf("1\n"); pthread_t threadT; pthread_attr_t attr; pthread_attr_init (&attr); pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_JOINABLE); pthread_create(&threadT,NULL,&foo,(void*)NULL); printf("2\n"); while (!feof(stdin)){ int id, in, out; fscanf(stdin,"%d:%d:%d",&id,&in,&out); } } int main(){ pthread_attr_t attr; pthread_attr_init (&attr); pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_JOINABLE); pthread_t threadT; pthread_create(&vlaknoVstupu,&attr,&threadF,(void*)&data); pthread_join(threadT,NULL); pthread_attr_destroy (&attr); } // I skipped irelevant parts of code... the thing is, that sometimes, the output is 12foo, but usually just 12. Then the function waits for input. I would expect it to be always 12foo. Do anybody know why are my expectations wrong?

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  • How to migrate primary key generation from "increment" to "hi-lo"?

    - by Bevan
    I'm working with a moderate sized SQL Server 2008 database (around 120 tables, backups are around 4GB compressed) where all the table primary keys are declared as simple int columns. At present, primary key values are generated by NHibernate with the increment identity generator, which has worked well thus far, but precludes moving to a multiprocessing environment. Load on the system is growing, so I'm evaluating the work required to allow the use of multiple servers accessing a common database backend. Transitioning to the hi-lo generator seems to be the best way forward, but I can't find a lot of detail about how such a migration would work. Will NHibernate automatically create rows in the hi-lo table for me, or do I need to script these manually? If NHibernate does insert rows automatically, does it properly take account of existing key values? If NHibernate does take care of thing automatically, that's great. If not, are there any tools to help? Update NHibernate's increment identifier generator works entirely in-memory. It's seeded by selecting the maximum value of used identifiers from the table, but from that point on allocates new values by a simple increment, without reference back to the underlying database table. If any other process adds rows to the table, you end up with primary key collisions. You can run multiple threads within the one process just fine, but you can't run multiple processes. For comparison, the NHibernate identity generator works by configuring the database tables with identity columns, putting control over primary key generation in the hands of the database. This works well, but compromises the unit of work pattern. The hi-lo algorithm sits inbetween these - generation of primary keys is coordinated through the database, allowing for multiprocessing, but actual allocation can occur entirely in memory, avoiding problems with the unit of work pattern.

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  • using volatile keyword

    - by sap
    As i understand, if we declare a variable as volatile, then it will not be stored in the local cache. Whenever thread are updating the values, it is updated to the main memory. So, other threads can access the updated value. But in the following program both volatile and non-volatile variables are displaying same value. The volatile variable is not updated for the second thread. Can anybody plz explain this why testValue is not changed. class ExampleThread extends Thread { private int testValue1; private volatile int testValue; public ExampleThread(String str){ super(str); } public void run() { if (getName().equals("Thread 1 ")) { testValue = 10; testValue1= 10; System.out.println( "Thread 1 testValue1 : " + testValue1); System.out.println( "Thread 1 testValue : " + testValue); } if (getName().equals("Thread 2 ")) { System.out.println( "Thread 2 testValue1 : " + testValue1); System.out.println( "Thread 2 testValue : " + testValue); } } } public class VolatileExample { public static void main(String args[]) { new ExampleThread("Thread 1 ").start(); new ExampleThread("Thread 2 ").start(); } } output: Thread 1 testValue1 : 10 Thread 1 testValue : 10 Thread 2 testValue1 : 0 Thread 2 testValue : 0

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  • How do JVM's implicit memory barriers behave when chaining constructors

    - by Joonas Pulakka
    Referring to my earlier question on incompletely constructed objects, I have a second question. As Jon Skeet pointed out, there's an implicit memory barrier in the end of a constructor that makes sure that final fields are visible to all threads. But what if a constructor calls another constructor; is there such a memory barrier in the end of each of them, or only in one being called from outside? That is, when the "wrong" solution is: public class ThisEscape { public ThisEscape(EventSource source) { source.registerListener( new EventListener() { public void onEvent(Event e) { doSomething(e); } }); } } And the correct one would be a factory method version: public class SafeListener { private final EventListener listener; private SafeListener() { listener = new EventListener() { public void onEvent(Event e) { doSomething(e); } } } public static SafeListener newInstance(EventSource source) { SafeListener safe = new SafeListener(); source.registerListener(safe.listener); return safe; } } Would the following work too, or not? public class MyListener { private final EventListener Listener; private MyListener() { listener = new EventListener() { public void onEvent(Event e) { doSomething(e); } } } public MyListener(EventSource source) { this(); source.register(listener); } }

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  • Tricky MySQL Query for messaging system in Rails - Please Help

    - by ole_berlin
    Hi, I'm writing a facebook style messaging system for a Rails App and I'm having trouble selecting the Messages for the inbox (with will_paginate). The messages are organized in threads, in the inbox the most recent message of a thread will appear with a link to it's thread. The thread is organized via a parent_id 1-n relationship with itself. So far I'm using something like this: class Message < ActiveRecord::Base belongs_to :sender, :class_name => 'User', :foreign_key => "sender_id" belongs_to :recipient, :class_name => 'User', :foreign_key => "recipient_id" has_many :children, :class_name => "Message", :foreign_key => "parent_id" belongs_to :thread, :class_name => "Message", :foreign_key => "parent_id" end class MessagesController < ApplicationController def inbox @messages = current_user.received_messages.paginate :page => params[:page], :per_page => 10, :order => "created_at DESC" end end That gives me all the messages, but for one thread the thread itself and the most recent message will appear (and not only the most recent message). I can also not use the GROUP BY clause, because for the thread itself (the parent so to say) the parent_id = nil of course. Anyone got an idea on how to solve this in an elegant way? I already thought about adding the parent_id to the parent itself and then group by parent_id, but I'm not sure if that works. Thanks

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  • ExecutorService memory leak on exception

    - by TofuBeer
    I am having a hard time tracking this down since the profiler keeps crashing (hotspot error). Before I go too deep into figuring it out I'd like to know if I really have a problem or not :-) I have a few thread pools created via: Executors.newFixedThreadPool(10); The threads connect to different web sites and, on occasion, I get connection refused and wind up throwing an exception. When I later on call Future.get() to get the result it will then catch the ExecutionException that wraps the exception that was thrown when the connection could not be made. The program uses a fairly constant amount of memory up until the point in time that the exceptions get thrown (they tend to happen in batches when a particular site is overloaded). After that point the memory again remains constant but at a higher level. So my question is along the lines of is the memory behaviour (reported by "top" on Unix) expected because the exceptions just triggered something or do I probably have an actual leak that I'll need to track down? Additionally when Future.get() throws an exception is there anything else I need to do besides catch the exception (such as call Future.cancel() on it)?

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  • Does Android AsyncTaskQueue or similar exist?

    - by Ben L.
    I read somewhere (and have observed) that starting threads is slow. I always assumed that AsyncTask created and reused a single thread because it required being started inside the UI thread. The following (anonymized) code is called from a ListAdapter's getView method to load images asynchronously. It works well until the user moves the list quickly, and then it becomes "janky". final File imageFile = new File(getCacheDir().getPath() + "/img/" + p.image); image.setVisibility(View.GONE); view.findViewById(R.id.imageLoading).setVisibility(View.VISIBLE); (new AsyncTask<Void, Void, Bitmap>() { @Override protected Bitmap doInBackground(Void... params) { try { Bitmap image; if (!imageFile.exists() || imageFile.length() == 0) { image = BitmapFactory.decodeStream(new URL( "http://example.com/images/" + p.image).openStream()); image.compress(Bitmap.CompressFormat.JPEG, 85, new FileOutputStream(imageFile)); image.recycle(); } image = BitmapFactory.decodeFile(imageFile.getPath(), bitmapOptions); return image; } catch (MalformedURLException ex) { // TODO Auto-generated catch block ex.printStackTrace(); return null; } catch (IOException ex) { // TODO Auto-generated catch block ex.printStackTrace(); return null; } } @Override protected void onPostExecute(Bitmap image) { if (view.getTag() != p) // The view was recycled. return; view.findViewById(R.id.imageLoading).setVisibility( View.GONE); view.findViewById(R.id.image) .setVisibility(View.VISIBLE); ((ImageView) view.findViewById(R.id.image)) .setImageBitmap(image); } }).execute(); I'm thinking that a queue-based method would work better, but I'm wondering if there is one or if I should attempt to create my own implementation.

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  • can i know the Thread runnable class attributes in java?

    - by dori naji
    probability this question have been asked before but i cant find anything in my searching mechanism. I am trying to create a multiple threads, in an array list but i want to retrieve them from an arraylist and filter them by the attribute of w1 i used in my code. any ideas ? w1 = new FirstWorker(ProductsList, OrdersList, s); FirstWorkerThread = new Thread(w1); ThreadArrayList.add(FirstWorkerThread); //I know i cant do the code below but i want to do that how ? for(Thread x : ThreadArrayList){ x.ProductsList } this is FirstWorker class import java.lang.String; import java.util.HashMap; /* * To change this template, choose Tools | Templates and open the template in * the editor. */ /** * * @author Dimitris */ public class FirstWorker extends Thread implements Runnable { private OrderList orderlist; private ProductList productlist; private String Worker; boolean Stop; private int speed = 1000; public FirstWorker(ProductList productlist, OrderList orderlist, String Worker) { this.productlist = productlist; this.orderlist = orderlist; this.Worker = Worker; this.Stop = true; } public void run() { if (Stop == true) { try { Thread.sleep(100); } catch (InterruptedException e) { } while (orderlist.returnLengthofOrder() != 0) { if (Thread.interrupted()) { System.out.println("I am in the thread inturrupt"); // We've been interrupted: no more crunching. return; } if (orderlist.getDone() == true) { } else if (orderlist.getDone() == false) { orderlist.setDoneTrue(); orderlist.Purchased(Worker); orderlist.setDoneFalse(); try { Thread.sleep(this.speed); } catch (InterruptedException e) { return; } } } } } public void setWork() { Stop = false; } public void setSpeed(int speed) { this.speed = speed; } }

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  • InvalidOperationException when executing SqlCommand with transaction

    - by Serhat Özgel
    I have this code, running parallel in two separate threads. It works fine for a few times, but at some random point it throws InvalidOperationException: The transaction is either not associated with the current connection or has been completed. At the point of exception, I am looking inside the transaction with visual studio and verify its connection is set normally. Also command.Transaction._internalTransaction. _transactionState is set to Active and IsZombied property is set to false. This is a test application and I am using Thread.Sleep for creating longer transactions and causing overlaps. Why may the exception being thrown and what can I do about it? IDbCommand command = new SqlCommand("Select * From INFO"); IDbConnection connection = new SqlConnection(connectionString); command.Connection = connection; IDbTransaction transaction = null; try { connection.Open(); transaction = connection.BeginTransaction(); command.Transaction = transaction; command.ExecuteNonQuery(); // Sometimes throws exception Thread.Sleep(forawhile); // For overlapping transactions running in parallel transaction.Commit(); } catch (ApplicationException exception) { if (transaction != null) { transaction.Rollback(); } } finally { connection.Close(); }

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  • MySQL LEFT JOIN, INNER JOIN etc, complicated query, PHP + MySQL for a forum

    - by Sven Eriksson
    So I've got a little forum I'm trying to get data for, there are 4 tables, forum, forum_posts, forum_threads and users. What i'm trying to do is to get the latest post for each forum and giving the user a sneak peek of that post, i want to get the number of posts and number of threads in each forum aswell. Also, i want to do this in one query. So here's what i came up with: SELECT lfx_forum_posts.*, lfx_forum.*, COUNT(lfx_forum_posts.pid) as posts_count, lfx_users.username, lfx_users.uid, lfx_forum_threads.tid, lfx_forum_threads.parent_forum as t_parent, lfx_forum_threads.text as t_text, COUNT(lfx_forum_threads.tid) as thread_count FROM lfx_forum LEFT JOIN (lfx_forum_threads INNER JOIN (lfx_forum_posts INNER JOIN lfx_users ON lfx_users.uid = lfx_forum_posts.author) ON lfx_forum_threads.tid = lfx_forum_posts.parent_thread AND lfx_forum_posts.pid = (SELECT MAX(lfx_forum_posts.pid) FROM lfx_forum_posts WHERE lfx_forum_posts.parent_forum = lfx_forum.fid GROUP BY lfx_forum_posts.parent_forum) ) ON lfx_forum.fid = lfx_forum_posts.parent_forum GROUP BY lfx_forum.fid ORDER BY lfx_forum.fid ASC This get the latest post in each forum and gives me a sneakpeek of it, the problem is that lfx_forum_posts.pid = (SELECT MAX(lfx_forum_posts.pid) FROM lfx_forum_posts WHERE lfx_forum_posts.parent_forum = lfx_forum.fid GROUP BY lfx_forum_posts.parent_forum) Makes my COUNT(lfx_forum_posts.pid) go to one (aswell as the COUNT(lfx_forum_threads.tid) which isn't how i would like it to work. My question is: is there some somewhat easy way to make it show the correct number and at the same time fetch the correct post info (the latest one that is)? If something is unclear please tell and i'll try to explain my issue further, it's my first time posting something here.

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  • Generating SQL change scripts in SSMS 2008

    - by Munish Goyal
    I have gone through many related SO threads and got some basic info. Already generated DB diagram. After that i am unable to find a button/option to generate SQL scripts (create) for all the tables in diagram. "Generate script" button is disabled, even on clicking the table in diagram. However i enabled the auto-generate option in tools-designer. But what to do with previous diagrams. I just want an easy way to auto-generate such scripts (create/alter) and would be gud if i get auto-generated stored procs for insert/selects/update etc. EDIT: I could do generate scripts for DB objects. Now: 1. How to import DB diagram from another DB. 2. How to generate (and manage their change integrated with VS source control) routine stored-procs like insert, update and select. Ok let me ask another way, can experts guide on the usual flow of creating/altering tables (across releases), creating stored-procs (are stored-procs the best way to go ?) and their change-management using SSMS design tools and minimal effort ?

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