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• wpf command pattern

  - by evan

  I have a wpf gui which displays a list of information in separate window and in a separate thread from the main application. As the user performs actions in the main window the side window is updated. (For example if you clicked page down in the main window a listbox in the side window would page down). Right now the architecture for this application feels very messy and I'm sure there is a cleaner way to do it. It looks like this: Main Window contains a singleton SideWindowControl which communicates with an instance of the SideWindowDisplay using events - so, for example, the pagedown button would work like: 1) the event handler of the button on the main window calls SideWindowControl.PageDown() 2) in the PageDown() function a event is created and thrown. 3) finally the gui, ShowSideWindowDisplay is subscribing to the SideWindowControl.Actions event handles the event and actually scrolls the listbox down - note because it is in a different thread it has to do that by running the command via Dispatcher.Invoke() This just seems like a very messy way to this and there must be a clearer way (The only part that can't change is that the main window and the side window must be on different threads). Perhaps using WPF commands? I'd really appreciate any suggestions!! Thanks

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• What is happening in Crockford's object creation technique?

  - by Chris Noe

  There are only 3 lines of code, and yet I'm having trouble fully grasping this: Object.create = function (o) { function F() {} F.prototype = o; return new F(); }; newObject = Object.create(oldObject); (from Prototypal Inheritance) 1) Object.create() starts out by creating an empty function called F. I'm thinking that a function is a kind of object. Where is this F object being stored? Globally I guess. 2) Next our oldObject, passed in as o, becomes the prototype of function F. Function (i.e., object) F now "inherits" from our oldObject, in the sense that name resolution will route through it. Good, but I'm curious what the default prototype is for an object, Object? Is that also true for a function-object? 3) Finally, F is instantiated and returned, becoming our newObject. Is the "new" operation strictly necessary here? Doesn't F already provide what we need, or is there a critical difference between function-objects and non-function-objects? Clearly it won't be possible to have a constructor function using this technique. What happens the next time Object.create() is called? Is global function F overwritten? Surely it is not reused, because that would alter previously configured objects. And what happens if multiple threads call Object.create(), is there any sort of synchronization to prevent race conditions on F?

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• Multithreaded linked list traversal

  - by Rob Bryce

  Given a (doubly) linked list of objects (C++), I have an operation that I would like multithread, to perform on each object. The cost of the operation is not uniform for each object. The linked list is the preferred storage for this set of objects for a variety of reasons. The 1st element in each object is the pointer to the next object; the 2nd element is the previous object in the list. I have solved the problem by building an array of nodes, and applying OpenMP. This gave decent performance. I then switched to my own threading routines (based off Windows primitives) and by using InterlockedIncrement() (acting on the index into the array), I can achieve higher overall CPU utilization and faster through-put. Essentially, the threads work by "leap-frog'ing" along the elements. My next approach to optimization is to try to eliminate creating/reusing the array of elements in my linked list. However, I'd like to continue with this "leap-frog" approach and somehow use some nonexistent routine that could be called "InterlockedCompareDereference" - to atomically compare against NULL (end of list) and conditionally dereference & store, returning the dereferenced value. I don't think InterlockedCompareExchangePointer() will work since I cannot atomically dereference the pointer and call this Interlocked() method. I've done some reading and others are suggesting critical sections or spin-locks. Critical sections seem heavy-weight here. I'm tempted to try spin-locks but I thought I'd first pose the question here and ask what other people are doing. I'm not convinced that the InterlockedCompareExchangePointer() method itself could be used like a spin-lock. Then one also has to consider acquire/release/fence semantics... Ideas? Thanks!

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• Is it possible to Kick off a java process under Windows Service with C#?

  - by Wing C. Chen

  I would like to wrap a java program into a windows service with C# using System.ServiceProcess.ServiceBase. So I came up with the following code: /// <summary> /// The main entry point for the application. /// </summary> static void Main() { System.ServiceProcess.ServiceBase.Run(new JavaLauncher()); } protected override void OnStart(string[] args) { Thread _thread; _thread = new Thread(StartService); _thread.Start(); base.OnStart(args); } protected override void OnStop() { Thread _thread; _thread = new Thread(StopService); _thread.Start(); base.OnStop(); } static public void StartService() { System.Diagnostics.Process proc = new System.Diagnostics.Process(); proc.EnableRaisingEvents = false; proc.StartInfo.FileName = "javaw"; proc.StartInfo.Arguments = config.generateLaunchCommand(); proc.Start(); } static public void StopService() { System.Diagnostics.Process proc = new System.Diagnostics.Process(); proc.EnableRaisingEvents = false; proc.StartInfo.FileName = "javaw"; proc.StartInfo.Arguments = "-jar stop.jar"; proc.Start(); } Firstly I had to use Threads in OnStart and OnStop. If not, an exception occurs complaining that the service is terminated because of doing nothing. Secondly, the service can be hooked up to windows smoothly. However, the service terminates a short while after it is started. I looked into the process monitor, only the service process stays alive for that short while, the javaw process never showed up, however. Is there anyone who knows how this can be fixed? It works fine in an ordinary console environment. I think it has something to do with Windows service.

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• Calling into a saved java object via JNI from a different thread

  - by Drake Amara

  I have a java object which calls into a C++ shared object via JNI. In C++, I am saving a reference to the JNIEnv and jObject. JavaVM * jvm; JNIEnv * myEnv; jobject myobj; JNIEXPORT void JNICALL Java_org_api_init (JNIEnv *env, jobject jObj) { myEnv = env; myobj = jObj; } I also have a GLSurface renderer and it eventually calls the C++ shared object mentioned above on a different thread, the GLThread. I am then trying to call back into my original Java object using the jobject I saved initially, but I think because I am on the GLThread, I get the following error. W/dalvikvm(16101): JNI WARNING: 0x41ded218 is not a valid JNI reference I/dalvikvm(16101): "GLThread 981" prio=5 tid=15 RUNNABLE I/dalvikvm(16101): | group="main" sCount=0 dsCount=0 obj=0x41d6e220 self=0x5cb11078 I/dalvikvm(16101): | sysTid=16133 nice=0 sched=0/0 cgrp=apps handle=1555429136 I/dalvikvm(16101): | schedstat=( 0 0 0 ) utm=42 stm=32 core=1 The code calling back into Java : void setData() { jvm->AttachCurrentThread(&myEnv, 0); jclass javaClass = myEnv->FindClass("com/myapp/myClass"); if(javaClass == NULL){ LOGD("ERROR - cant find class"); } jmethodID method = myEnv->GetMethodID(javaClass, "updateDataModel", "()V"); if(method == NULL){ LOGD("ERROR - cant access method"); } // this works, but its a new java object //jobject myobj2 = myEnv->NewObject(javaClass, method); //this is where the crash occurs myEnv->CallVoidMethod(myobj, method, NULL); } If instead I create a new jObject using env-NewObject, I can succuessfully call back into Java, but it is a new object and I dont want that. I need to get back to my original Java Object. Is it a matter of switching threads before I call back into Java? If so, how do I do so ?

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• What is the simplest way to implement multithreading in c# to existing code

  - by Kaeso

  I have already implemented a functionnal application that parses 26 pages of html all at once to produce an xml file with data contained on the web pages. I would need to implement a thread so that this method can work in the background without causing my app to seems unresponsive. Secondly, I have another function that is decoupled from the first one which compares two xml files to produce a third one and then transform this third xml file to produce an html page using XSLT. This would have to be on a thread, where I can click Cancel to stop the thread whithout crashing the app. What is the easiest best way to do this using WPF forms in VS 2010 ? I have chosen to use the BackgroundWorker. BackgroundWorker implementation: public partial class MainWindow : Window { private BackgroundWorker bw = new BackgroundWorker(); public MainWindow() { InitializeComponent(); bw.WorkerReportsProgress = true; bw.DoWork += new DoWorkEventHandler(bw_DoWork); bw.RunWorkerCompleted += new RunWorkerCompletedEventHandler(backgroundWorker1_RunWorkerCompleted); } private void Window_Loaded(object sender, RoutedEventArgs e) { this.LoadFiles(); } private void btnCompare_Click(object sender, EventArgs e) { if (bw.IsBusy != true) { progressBar2.IsIndeterminate = true; // Start the asynchronous operation. bw.RunWorkerAsync(); } } private void bw_DoWork(object sender, DoWorkEventArgs e) { StatsProcessor proc = new StatsProcessor(); if (lstStatsBox1.SelectedItem != null) if (lstStatsBox2.SelectedItem != null) proc.CompareStats(lstStatsBox1.SelectedItem.ToString(), lstStatsBox2.SelectedItem.ToString()); } private void backgroundWorker1_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e) { progressBar2.IsIndeterminate = false; progressBar2.Value = 100; } I have started with the bgworker solution, but it seems that the bw_DoWork method is never called when btnCompare is clicked, I must be doing something wrong... I am new to threads.

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• Thread synchronization and aborting.

  - by kubal5003

  Hello, I've got a little problem with ending the work of one of my threads. First things first so here's the app "layout": Thread 1 - worker thread (C++/CLI) - runs and terminates as expected for(...) { try { if(TabuStop) return; System::Threading::Monitor::Enter("Lock1"); //some work, unmanaged code } finally { if(stop) { System::Threading::Monitor::Pulse("Lock1"); } else { System::Threading::Monitor::Pulse("Lock1"); System::Threading::Monitor::Wait("Lock1"); } } } Thread 2 - display results thread (C#) while (WorkerThread.IsAlive) { lock ("Lock1") { if (TabuEngine.TabuStop) { Monitor.Pulse("Lock1"); } else { Dispatcher.BeginInvoke(RefreshAction); Monitor.Pulse("Lock1"); Monitor.Wait("Lock1", 5000); } } // Thread.Sleep(5000); } I'm trying to shut the whole thing down from app main thread like this: TabuEngine.TabuStop = true; //terminates nicely the worker thread and if (DisplayThread.IsAlive) { DisplayThread.Abort(); } I also tried using DisplayThread.Interrupt, but it always blocks on Monitor.Wait("Lock1", 5000); and I can't get rid of it. What is wrong here? How am I supposed to perform the synchronization and let it do the work that it is supposed to do? //edit I'm not even sure now if the trick with using "Lock1" string is really working and locks are placed on the same object..

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• Doubly Linked Lists Implementation

  - by user552127

  Hi All, I have looked at most threads here about Doubly linked lists but still unclear about the following. I am practicing the Goodrich and Tamassia book in Java. About doubly linked lists, please correct me if I am wrong, it is different from a singly linked list in that a node could be inserted anywhere, not just after the head or after the tail using both the next and prev nodes available, while in singly linked lists, this insertion anywhere in the list is not possible ? If one wants to insert a node in a doubly linked list, then the default argument should be either the node after the to-be inserted node or node before the to-be inserted node ? But if this is so, then I don't understand how to pass the node before or after. Should we be displaying all nodes that were inserted till now and ask the user to select the node before or after which some new node is to be inserted ? My doubt is how to pass this default node. Because I assume that will require the next and prev nodes of these nodes as well. For e.g, Head<-A<-B<-C<-D<-E<-tail If Z is the new node to be inserted after say D, then how should node D be passed ? I am confused with this though it seems pretty simple to most. But pl do explain. Thanks, Sanjay

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• How to find out where a thread lock happend?

  - by SchlaWiener

  One of our company's Windows Forms application had a strange problem for several month. The app worked very reliable for most of our customers but on some PC's (mostly with a wireless lan connection) the app sometimes just didn't respond anymore. (You click on the UI and windows ask you to wait or kill the app). I wasn't able to track down the problem for a long time but now I figured out what happend. The app had this line of code // don't blame me for this. Wasn't my code :D Control.CheckForIllegalCrossThreadCalls = false and used some background threads to modify the controls. No I found a way to reproduce the application stopping responding bug on my dev machine and tracked it down to a line where I actually used Invoke() to run a task in the main thread. Me.Invoke(MyDelegate, arg1, arg2) Obviously there was a thread lock somewhere. After removing the Control.CheckForIllegalCrossThreadCalls = false statement and refactoring the whole programm to use Invoke() if modifying a control from a background thread, the problem is (hopefully) gone. However, I am wondering if there is a way to find such bugs without debugging every line of code (Even if I break into debugger after the app stops responding I can't tell what happend last, because the IDE didn't jump to the Invoke() statement) In other words: If my apps hangs how can I figure out which line of code has been executed last? Maybe even on the customers PC. I know VS2010 offers some backwards debugging feature, maybe that would be a solution, but currently I am using VS2008.

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• OpenMP in Fortran

  - by user345293

  I very rarely use fortran, however I have been tasked with taking legacy code rewriting it to run in parallel. I'm using gfortran for my compiler choice. I found some excellent resources at https://computing.llnl.gov/tutorials/openMP/ as well as a few others. My problem is this, before I add any OpenMP directives, if I simply compile the legacy program: gfortran Example1.F90 -o Example1 everything works, but turning on the openmp compiler option even without adding directives: gfortran -openmp Example1.F90 -o Example1 ends up with a Segmentation fault when I run the legacy program. Using smaller test programs that I wrote, I've successfully compiled other programs with -openmp that run on multiple threads, but I'm rather at a loss why enabling the option alone and no directives is resulting in a seg fault. I apologize if my question is rather simple. I could post code but it is rather long. It faults as I assign initial values: REAL, DIMENSION(da,da) :: uconsold REAL, DIMENSION(da,da,dr,dk) :: uconsolde ... uconsold=0.0 uconsolde=0.0 The first assignment to "uconsold" works fine, the second seems to be the source of the fault as when I comment the line out the next several lines execute merrily until "uconsolde" is used again. Thank you for any help in this matter.

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• g-wan - reproducing the performance claims

  - by user2603628

  Using gwan_linux64-bit.tar.bz2 under Ubuntu 12.04 LTS unpacking and running gwan then pointing wrk at it (using a null file null.html) wrk --timeout 10 -t 2 -c 100 -d20s http://127.0.0.1:8080/null.html Running 20s test @ http://127.0.0.1:8080/null.html 2 threads and 100 connections Thread Stats Avg Stdev Max +/- Stdev Latency 11.65s 5.10s 13.89s 83.91% Req/Sec 3.33k 3.65k 12.33k 75.19% 125067 requests in 20.01s, 32.08MB read Socket errors: connect 0, read 37, write 0, timeout 49 Requests/sec: 6251.46 Transfer/sec: 1.60MB .. very poor performance, in fact there seems to be some kind of huge latency issue. During the test gwan is 200% busy and wrk is 67% busy. Pointing at nginx, wrk is 200% busy and nginx is 45% busy: wrk --timeout 10 -t 2 -c 100 -d20s http://127.0.0.1/null.html Thread Stats Avg Stdev Max +/- Stdev Latency 371.81us 134.05us 24.04ms 91.26% Req/Sec 72.75k 7.38k 109.22k 68.21% 2740883 requests in 20.00s, 540.95MB read Requests/sec: 137046.70 Transfer/sec: 27.05MB Pointing weighttpd at nginx gives even faster results: /usr/local/bin/weighttp -k -n 2000000 -c 500 -t 3 http://127.0.0.1/null.html weighttp - a lightweight and simple webserver benchmarking tool starting benchmark... spawning thread #1: 167 concurrent requests, 666667 total requests spawning thread #2: 167 concurrent requests, 666667 total requests spawning thread #3: 166 concurrent requests, 666666 total requests progress: 9% done progress: 19% done progress: 29% done progress: 39% done progress: 49% done progress: 59% done progress: 69% done progress: 79% done progress: 89% done progress: 99% done finished in 7 sec, 13 millisec and 293 microsec, 285172 req/s, 57633 kbyte/s requests: 2000000 total, 2000000 started, 2000000 done, 2000000 succeeded, 0 failed, 0 errored status codes: 2000000 2xx, 0 3xx, 0 4xx, 0 5xx traffic: 413901205 bytes total, 413901205 bytes http, 0 bytes data The server is a virtual 8 core dedicated server (bare metal), under KVM Where do I start looking to identify the problem gwan is having on this platform ? I have tested lighttpd, nginx and node.js on this same OS, and the results are all as one would expect. The server has been tuned in the usual way with expanded ephemeral ports, increased ulimits, adjusted time wait recycling etc.

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• Design an Application That Stores and Processes Files

  - by phasetwenty

  I'm tasked with writing an application that acts as a central storage point for files (usually document formats) as provided by other applications. It also needs to take commands like "file 395 needs a copy in X format", at which point some work is offloaded to a 3rd party application. I'm having trouble coming up with a strategy for this. I'd like to keep the design as simple as possible, so I'd like to avoid big extra frameworks or techniques like threads for as long as it makes sense. The clients are expected to be web applications (for example, one is a django application that receives files from our customers; the others are not yet implemented). The platform it will be running on is likely going to be Python on Linux, unless I have a strong argument to use something else. In the beginning I thought I could fit the information I wanted to communicate in the filenames, and let my application parse the filename to figure out what it needed to do, but this is proving too inflexible with the amount of information I'm realizing I need to make available. Another idea is to pair FTP with a database used as a communication medium (client uploads a file and updates the database with a command as a row in a table) but I don't like this idea because adding commands (a known change) looks like it will require adding code as well as changing database schemas. It will also muddy up the interface my clients will have to use. I looked into Pyro to let applications communicate more directly but I don't like the idea of running an extra nameserver for this one purpose. I also don't see a good way to do file transfer within this framework. What I'm looking for is techniques and/or technologies applicable to my problem. At the simplest level, I need the ability to accept files and messages with them.

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• Help with SQL query (Calculate a ratio between two entitiess)

  - by Mestika

  Hi, I’m going to calculate a ratio between two entities but are having some trouble with the query. The principal is the same to, say a forum, where you say: A user gets points for every new thread. Then, calculate the ratio of points for the number of threads. Example: User A has 300 points. User A has started 6 thread. The point ratio is: 50:6 My schemas look as following: student(studentid, name, class, major) course(courseid, coursename, department) courseoffering(courseid, semester, year, instructor) faculty(name, office, salary) gradereport(studentid, courseid, semester, year, grade) The relations is a following: Faculity(name) = courseoffering(instructor) Student(studentid) = gradereport (studentid) Courseoffering(courseid) = course(courseid) Gradereport(courseid) = courseoffering(courseid) I have this query to select the faculty names there is teaching one or more students: SELECT COUNT(faculty.name) FROM faculty, courseoffering, gradereport, student WHERE faculty.name = courseoffering.instructor AND courseoffering.courseid = gradereport.courseid AND gradereport.studentid = student.studentid My problem is to find the ratio between the faculty members salary in regarding to the number of students they are teaching. Say, a teacher get 10.000 in salary and teaches 5 students, then his ratio should be 1:5. I hope that someone has an answer to my problem and understand what I'm having trouble with. Thanks Mestika

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• Can we run two simultaneous non-nested loops in Perl?

  - by Mike

  Part of my code goes like this: while(1){ my $winmm = new Win32::MediaPlayer; $winmm->load('1.mp3'); $winmm->play; $winmm->volume(100); Do Some Stuff; last if some condition is met; } Problem is: I want the music to be always on when I'm in the Do Some Stuff stage in the while loop. But the length of the music is so short that it will come to a full stop before I go to the next stage, so I want the music to repeat itself, but the Win32::Mediaplayer module does not seem to have a repeat mode, so I'm thinking of doing an infinite loop for the music playing part. Like this: while(1){ my $winmm = new Win32::MediaPlayer; $winmm->load('1.mp3'); $winmm->play; $winmm->volume(100); } while(2){ Do some stuff; last if some condition is met } But based on my current Perl knowledge if I'm in the while(1) part, I can never go to the while(2) part. Even if it comes to a nested loop, I have to do something to break out of the inside loop before going to the other part of the outside loop. The answer to my question "Can we run two simultaneous non-nested loops in Perl?" may be a NO, but I assume there is some way of handling such situation. Correct me if I'm wrong. Thanks as always for any comments/suggestions :) UPDATE I really appreciate the help from everyone. Thanks :) So the answer to my question is a YES, not a NO. I'm happy that I've learned how to use fork() and threads to solve a real problem :)

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• PHP in_array() can't even match a single character. Strict is set to true.

  - by solefald

  I've seen a million of these threads here already, and read through every single one already. Including some serious time Googling. Nothing complicated. All I have to do is check if a single character in a loop matches my alphabet array. print_r($alphabet); // all 26 letters Array ( [0] => a [1] => b [2] => c ... [23] => x [24] => y [25] => z ) print_r($emptyLetters); // dynamic array. Array ( [0] => b [1] => s ) foreach($alphabet as $letter): { echo $letter . '<br />' // Correctly prints out every letter from $alphabet. if(in_array($letter, $emptyLetters, true)): // $strict is set // do something endif; } What the hell is going on??? I do not understand what i am doing wrong.... I tried every combination and option possible, but for some reason even array_search() is bit working...

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• How to properly handle signals when using the worker thread pattern?

  - by ipartola

  I have a simple server that looks something like this: void *run_thread(void *arg) { // Communicate via a blocking socket } int main() { // Initialization happens here... // Main event loop while (1) { new_client = accept(socket, ...); pthread_create(&thread, NULL, &run_thread, *thread_data*); pthread_detach(thread); } // Do cleanup stuff: close(socket); // Wait for existing threads to finish exit(0); ) Thus when a SIGINT or SIGTERM is received I need to break out of the main event loop to get to the clean up code. Moreover most likely the master thread is waiting on the accept() call so it's not able to check some other variable to see if it should break;. Most of the advice I found was along the lines of this: http://devcry.blogspot.com/2009/05/pthreads-and-unix-signals.html (creating a special signal handling thread to catch all the signals and do processing on those). However, it's the processing portion that I can't really wrap my head around: how can I possibly tell the main thread to return from the accept() call and check on an external variable to see if it should break;?

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• Multithreading using pthread in C++ with shared variables

  - by Saviour Self

  I'm new to threading (and C/C++ for that matter), and I'm attempting to use multiple threads to access shared variables. In the main, I've created a variable char inputarray[100]; Thread 1: This thread will be reading data from stdin in 2 byte bursts, and appending them to the inputarray. (input by feeding a file in) Thread 2: This thread will be reading data 1 byte at a time, performing a calculation, and putting its data into an output array. Thread 3: This thread will be outputting data from the output array in 2 byte bursts. (stdout) I've attempted the input part and got it working by passing a struct, but would like to do it without using a struct, but it has been giving me problems. If I can get input down, I'm sure I'll be able to use a similar strategy to complete output. Any help would be greatly appreciated. Below is a rough template for the input thread. #include <stdio.h> #include <pthread.h> using namespace std; void* input(void* arg) { char reading[3]; fread(reading,1,2,stdin); //append to char inputarray[]..??? } int main() { char inputarray[100]; pthread_t t1; pthread_create(&t1, NULL, &input, &inputarray); void *result; pthread_join(t1,&result); return 0; }

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• Concurrency problem with arrays (Java)

  - by Johannes

  For an algorithm I'm working on I tried to develop a blacklisting mechanism that can blacklist arrays in a specific way: If "1, 2, 3" is blacklisted "1, 2, 3, 4, 5" is also considered blacklisted. I'm quite happy with the solution I've come up with so far. But there seem to be some serious problems when I access a blacklist from multiple threads. The method "contains" (see code below) sometimes returns true, even if an array is not blacklisted. This problem does not occur if I only use one thread, so it most likely is a concurrency problem. I've tried adding some synchronization, but it didn't change anything. I also tried some slightly different implementations using java.util.concurrent classes. Any ideas on how to fix this? public class Blacklist { private static final int ARRAY_GROWTH = 10; private final Node root = new Node(); private static class Node{ private volatile Node[] childNodes = new Node[ARRAY_GROWTH]; private volatile boolean blacklisted = false; public void blacklist(){ this.blacklisted = true; this.childNodes = null; } } public void add(final int[] array){ synchronized (root) { Node currentNode = this.root; for(final int edge : array){ if(currentNode.blacklisted) return; else if(currentNode.childNodes.length <= edge) { currentNode.childNodes = Arrays.copyOf(currentNode.childNodes, edge + ARRAY_GROWTH); } if(currentNode.childNodes[edge] == null) { currentNode.childNodes[edge] = new Node(); } currentNode = currentNode.childNodes[edge]; } currentNode.blacklist(); } } public boolean contains(final int[] array){ synchronized (root) { Node currentNode = this.root; for(final int edge : array){ if(currentNode.blacklisted) return true; else if(currentNode.childNodes.length <= edge || currentNode.childNodes[edge] == null) return false; currentNode = currentNode.childNodes[edge]; } return currentNode.blacklisted; } } }

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• cython setup.py gives .o instead of .dll

  - by alok1974

  Hi, I am a newbie to cython, so pardon me if I am missing something obvious here. I am trying to build c extensions to be used in python for enhanced performance. I have fc.py module with a bunch of function and trying to generate a .dll through cython using dsutils and running on win64: c:\python26\python c:\cythontest\setup.py build_ext --inplace I have the dsutils.cfg in C:\Python26\Lib\distutils. As required the disutils.cfg has the following config settings: [build] compiler = mingw32 My startup.py looks like this: from distutils.core import setup from distutils.extension import Extension from Cython.Distutils import build_ext ext_modules = [Extension('fc', [r'C:\cythonTest\fc.pyx'])] setup( name = 'FC Extensions', cmdclass = {'build_ext': build_ext}, ext_modules = ext_modules ) I have latest version mingw for target/host amdwin64 type builds. I have the latest version of cython for python26 for win64. Cython does give me an fc.c without errors, only a few warning for type conversions, which I will handle once I have it right. Further it produces fc.def an fc.o files Instead of giving a .dll. I get no errors. I find on threads that it will create the .so or .dll automatically as required, which is not happening.

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• What about parallelism across network using multiple PCs?

  - by MainMa

  Parallel computing is used more and more, and new framework features and shortcuts make it easier to use (for example Parallel extensions which are directly available in .NET 4). Now what about the parallelism across network? I mean, an abstraction of everything related to communications, creation of processes on remote machines, etc. Something like, in C#: NetworkParallel.ForEach(myEnumerable, () => { // Computing and/or access to web ressource or local network database here }); I understand that it is very different from the multi-core parallelism. The two most obvious differences would probably be: The fact that such parallel task will be limited to computing, without being able for example to use files stored locally (but why not a database?), or even to use local variables, because it would be rather two distinct applications than two threads of the same application, The very specific implementation, requiring not just a separate thread (which is quite easy), but spanning a process on different machines, then communicating with them over local network. Despite those differences, such parallelism is quite possible, even without speaking about distributed architecture. Do you think it will be implemented in a few years? Do you agree that it enables developers to easily develop extremely powerfull stuff with much less pain? Example: Think about a business application which extracts data from the database, transforms it, and displays statistics. Let's say this application takes ten seconds to load data, twenty seconds to transform data and ten seconds to build charts on a single machine in a company, using all the CPU, whereas ten other machines are used at 5% of CPU most of the time. In a such case, every action may be done in parallel, resulting in probably six to ten seconds for overall process instead of forty.

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• PHP Check slave status without mysql_connect timeout issues

  - by Jonathon

  I have a web-app that has a master mysql db and four slave dbs. I want to handle all (or almost all) read-only (SELECT) queries from the slaves. Our load-balancer sends the user to one of the slave machines automatically, since they are also running Apache/PHP and serving webpages. I am using an include file to setup the connection to the databases, such as: //for master server (i.e. - UPDATE/INSERT/DELETE statements) $Host = "10.0.0.x"; $User = "xx"; $Password = "xx"; $Link = mysql_connect( $Host, $User, $Password ); if( !$Link ) ) { die( "Master database is currently unavailable. Please try again later." ); } //this connection can be used for READ-ONLY (i.e. - SELECT statements) on the localhost $Host_Local = "localhost"; $User_Local = "xx"; $Password_Local = "xx"; $Link_Local = mysql_connect( $Host_Local, $User_Local, $Password_Local ); //fail back to master if slave db is down if( !$Link_Local ) ) { $Link_Local = mysql_connect( $Host, $User, $Password ); } I then use $Link for all update queries and $Link_Local as the connection for SELECT statements. Everything works fine until the slave server database goes down. If the local db is down, the $Link_Local = mysql_connect() call takes at least 30 seconds before it gives up on trying to connect to the localhost and returns back to the script. This causes a huge backlog of page serves and basically shuts down the system (due to the extremely slow response time). Does anyone know of a better way to handle connections to slave servers via PHP? Or, is there some kind of timeout function that could be used to stop the mysql_connect call after 2-3 seconds? Thanks for the help. I searched the other mysql_connect threads, but didn't see any that addressed this issue.

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• Multithreaded Delegates/Events

  - by Matt

  I am trying to disable parts of the UI in a .NET app based on polling done on a background thread. The background thread checks to see if the global database connection the app uses is still open and operable. What I need to do, and would prefer to do it without polling on the UI thread, is to add an event handler that can be raised by the background thread if the connection status changes. That way, any form can have a handler that will disable those parts of the UI that require the connection to function. Attempting to use a straight event declaration in the class that holds the thread sub, and raising the event in the background thread causing cross-thread execution errors regarding accessing UI controls from other threads. Obviously, there is a correct way to do this, but we have limited experience with events (single threaded apps mainly), and almost none with delegates. I've read through documentation and examples for delegates, and it seems to be closer to what we need, but I'm not sure how to make it work in this instance. The app is written mainly in VB.NET, but an example or help in C# is fine too.

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• Do something else if ReadWriteSlimlock is held

  - by user43838

  Hi everyone, I have implemented ReaderWriterLockSlim, Now i don't want it to wait at the lock. I want to do something else if the lock is held. I considered using is isWriterLockHeld but it does not makes much sense to me, Since if two threads come in at the same time and enter the if statement at the same time one will still be waiting at the lock here is my code. ReaderWriterLockSlim rw = GetLoadingLock(parameters); rw = GetLoadingLock(parameters); try { rw.EnterWriteLock(); item = this.retrieveCacheItem(parameters.ToString(), false); if (item != null) { parameters.DataCameFromCache = true; // if the data was found in the cache, return it immediately return item.data; } else { try { object loaditem = null; itemsLoading[parameters.ToString()] = true; loaditem = this.retrieveDataFromStore(parameters); return loaditem; } finally { itemsLoading.Remove(parameters.ToString()); } } } finally { rw.ExitWriteLock(); } Can anyone please guide me in the right direction with this. Thanks

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• pthread_join from a signal handler

  - by liv2hak

  I have a capture program which in addition do capturing data and writing it into a file also prints some statistics.The function that prints the statistics static void* report(void) { /*Print statistics*/ } is called roughly every second using an ALARM that expires every second.So The program is like void capture_program() { pthread_t report_thread while(!exit_now) { if(pthread_create(&report_thread,NULL,report,NULL)){ fprintf(stderr,"Error creating reporting thread! \n"); } /* Capturing code -------------- -------------- */ if(doreport) usleep(5); } } void *report(void *param) { while(true) { if(doreport) { doreport = 0 //access some register from hardware usleep(5) } } } The expiry of the timer sets the doreport flag.If this flag is set report() is called which clears the flag.I am using usleep to alternate between two threads in the program.This seems to work fine. I also have a signal handler to handle SIGINT (i.e CTRL+C) static void anysig(int sig) { if (sig != SIGINT) dagutil_set_signal_handler(SIG_DFL); /* Tell the main loop to exit */ exit_now = 1; return; } My question: 1) Is it safe to call pthread_join from inside the signal handler? 2) Should I use exit_now flag for the report thread as well?

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• Apply [ThreadStatic] attribute to a method in external assembly

  - by Sen Jacob

  Can I use an external assembly's static method like [ThreadStatic] method? Here is my situation. The assembly class (which I do not have access to its source) has this structure public class RegistrationManager() { private RegistrationManager() {} public static void RegisterConfiguration(int ID) {} public static object DoWork() {} public static void UnregisterConfiguration(int ID) {} } Once registered, I cannot call the DoWork() with a different ID without unregistering the previously registered one. Actually I want to call the DoWork() method with different IDs simultaneously with multi-threading. If the RegisterConfiguration(int ID) method was [ThreadStatic], I could have call it in different threads without problems with calls, right? So, can I apply the [ThreadStatic] attribute to this method or is there any other way I can call the two static methods same time without waiting for other thread to unregister it? If I check it like the following, it should work. for(int i=0; i < 10; i++) { new Thread(new ThreadStart(() => Checker(i))).Start(); } public string Checker(int i) { public static void RegisterConfiguration(i); // Now i cannot register second time public static object DoWork(i); Thread.Sleep(5000); // DoWork() may take a little while to complete before unregistered public static void UnregisterConfiguration(i); }

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