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• Yet another C# Deadlock Debugging Question

  - by Roo

  Hi All, I have a multi-threaded application build in C# using VS2010 Professional. It's quite a large application and we've experienced the classing GUI cross-threading and deadlock issues before, but in the past month we've noticed the appears to lock up when left idle for around 20-30 minutes. The application is irresponsive and although it will repaint itself when other windows are dragged in front of the application and over it, the GUI still appears to be locked... interstingly (unlike if the GUI thread is being used for a considerable amount of time) the Close, Maximise and minimise buttons are also irresponsive and when clicked the little (Not Responding...) text is not displayed in the title of the application i.e. Windows still seems to think it's running fine. If I break/pause the application using the debugger, and view the threads that are running. There are 3 threads of our managed code that are running, and a few other worker threads whom the source code cannot be displayed for. The 3 threads that run are: The main/GUI thread A thread that loops indefinitely A thread that loops indefinitely If I step into threads 2 and 3, they appear to be looping correctly. They do not share locks (even with the main GUI thread) and they are not using the GUI thread at all. When stepping into the main/GUI thread however, it's broken on Application.Run... This problem screams deadlock to me, but what I don't understand is if it's deadlock, why can't I see the line of code the main/GUI thread is hanging on? Any help will be greatly appreciated! Let me know if you need more information... Cheers, Roo -----------------------------------------------------SOLUTION-------------------------------------------------- Okay, so the problem is now solved. Thanks to everyone for their suggestions! Much appreciated! I've marked the answer that solved my initial problem of determining where on the main/UI thread the application hangs (I handn't turned off the "Enable Just My Code" option). The overall issue I was experiencing was indeed Deadlock, however. After obtaining the call-stack and popping the top half of it into Google I came across this which explains exactly what I was experiencing... http://timl.net/ This references a lovely guide to debugging the issue... http://www.aaronlerch.com/blog/2008/12/15/debugging-ui/ This identified a control I was constructing off the GUI thread. I did know this, however, and was marshalling calls correctly, but what I didn't realise was that behind the scenes this Control was subscribing to an event or set of events that are triggered when e.g. a Windows session is unlocked or the screensaver exits. These calls are always made on the main/UI thread and were blocking when it saw the call was made on the incorrect thread. Kim explains in more detail here... http://krgreenlee.blogspot.com/2007/09/onuserpreferencechanged-hang.html In the end I found an alternative solution which did not require this Control off the main/UI thread. That appears to have solved the problem and the application no longer hangs. I hope this helps anyone who's confronted by a similar problem. Thanks again to everyone on here who helped! (and indirectly, the delightful bloggers I've referenced above!) Roo -----------------------------------------------------SOLUTION II-------------------------------------------------- Aren't threading issues delightful...you think you've solved it, and a month down the line it pops back up again. I still believe the solution above resolved an issue that would cause simillar behaviour, but we encountered the problem again. As we spent a while debugging this, I thought I'd update this question with our (hopefully) final solution: The problem appears to have been a bug in the Infragistics components in the WinForms 2010.1 release (no hot fixes). We had been running from around the time the freeze issue appeared (but had also added a bunch of other stuff too). After upgrading to WinForms 2010.3, we've yet to reproduce the issue (deja vu). See my question here for a bit more information: 'http://stackoverflow.com/questions/4077822/net-4-0-and-the-dreaded-onuserpreferencechanged-hang'. Hans has given a nice summary of the general issue. I hope this adds a little to the suggestions/information surrounding the nutorious OnUserPreferenceChanged Hang (or whatever you'd like to call it). Cheers, Roo

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• How can one manage to fully use the newly enhanced Parallelism features in .NET 4.0?

  - by Will Marcouiller

  I am pretty much interested into using the newly enhanced Parallelism features in .NET 4.0. I have also seen some possibilities of using it in F#, as much as in C#. Despite, I can only see what PLINQ has to offer with, for example, the following: var query = from c in Customers.AsParallel() where (c.Name.Contains("customerNameLike") select c; There must for sure be some other use of this parallelism thing. Have you any other examples of using it? Is this particularly turned toward PLINQ, or are there other usage as easy as PLINQ? Thanks! =)

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• How to synchronize cuda threads when they are in the same loop and we need to synchronize them to ex

  - by Vickey

  Hi all, I have written a code and Now I want to implement this on cuda GPU but I'm new to synchronization so please help me with this, It's little urgent to me. Below I'm presenting the code and I want to that LOOP1 to be executed by all threads (heance I want to this portion to take advantage of cuda and the remaining portion (the portion other from the LOOP1) is to be executed by only a single thread. do{ point_set = master_Q[(*num_mas) - 1].q; List* temp = point_set; List* pa = point_set; if(master_Q[num_mas[0] - 1].max) max_level = (int) (ceilf(il2 * log(master_Q[num_mas[0] - 1].max))); *num_mas = (*num_mas) - 1; while(point_set){ List* insert_ele = temp; while(temp){ insert_ele = temp; if((insert_ele->dist[insert_ele->dist_index-1] <= pow(2, max_level-1)) || (top_level == max_level)){ if(point_set == temp){ point_set = temp->next; pa = temp->next; } else{ pa->next = temp->next; } temp = NULL; List* new_point_set = point_set; float maximum_dist = 0; if(parent->p_index != insert_ele->point_index){ List* tmp = new_point_set; float *b = &(data[(insert_ele->point_index)*point_len]); **LOOP 1:** while(tmp){ float *c = &(data[(tmp->point_index)*point_len]); float sum = 0.; for(int j = 0; j < point_len; j+=2){ float d1 = b[j] - c[j]; float d2 = b[j+1] - c[j+1]; d1 *= d1; d2 *= d2; sum = sum + d1 + d2; } tmp->dist[tmp->dist_index] = sqrt(sum); if(maximum_dist < tmp->dist[tmp->dist_index]) maximum_dist = tmp->dist[tmp->dist_index]; tmp->dist_index = tmp->dist_index+1; tmp = tmp->next; } max_distance = maximum_dist; } while(new_point_set || insert_ele){ List* far, *par, *tmp, *tmp_new; far = NULL; tmp = new_point_set; tmp_new = NULL; float level_dist = pow(2, max_level-1); float maxdist = 0, maxp = 0; while(tmp){ if(tmp->dist[(tmp->dist_index)-1] > level_dist){ if(maxdist < tmp->dist[tmp->dist_index-1]) maxdist = tmp->dist[tmp->dist_index-1]; if(tmp == new_point_set){ new_point_set = tmp->next; par = tmp->next; } else{ par->next = tmp->next; } if(far == NULL){ far = tmp; tmp_new = far; } else{ tmp_new->next = tmp; tmp_new = tmp; } if(parent->p_index != insert_ele->point_index) tmp->dist_index = tmp->dist_index - 1; tmp = tmp->next; tmp_new->next = NULL; } else{ par = tmp; if(maxp < tmp->dist[(tmp->dist_index)-1]) maxp = tmp->dist[(tmp->dist_index)-1]; tmp = tmp->next; } } if(0 == maxp){ tmp = new_point_set; aloc_mem[*tree_index].p_index = insert_ele->point_index; aloc_mem[*tree_index].no_child = 0; aloc_mem[*tree_index].level = max_level--; parent->children_index[parent->no_child++] = *tree_index; parent = &(aloc_mem[*tree_index]); tree_index[0] = tree_index[0]+1; while(tmp){ aloc_mem[*tree_index].p_index = tmp->point_index; aloc_mem[(*tree_index)].no_child = 0; aloc_mem[(*tree_index)].level = master_Q[(*cur_count_Q)-1].level; parent->children_index[parent->no_child] = *tree_index; parent->no_child = parent->no_child + 1; (*tree_index)++; tmp = tmp->next; } cur_count_Q[0] = cur_count_Q[0]-1; new_point_set = NULL; } master_Q[*num_mas].q = far; master_Q[*num_mas].parent = parent; master_Q[*num_mas].valid = true; master_Q[*num_mas].max = maxdist; master_Q[*num_mas].level = max_level; num_mas[0] = num_mas[0]+1; if(0 != maxp){ aloc_mem[*tree_index].p_index = insert_ele->point_index; aloc_mem[*tree_index].no_child = 0; aloc_mem[*tree_index].level = max_level; parent->children_index[parent->no_child++] = *tree_index; parent = &(aloc_mem[*tree_index]); tree_index[0] = tree_index[0]+1; if(maxp){ int new_level = ((int) (ceilf(il2 * log(maxp)))) +1; if (new_level < (max_level-1)) max_level = new_level; else max_level--; } else max_level--; } if( 0 == maxp ) insert_ele = NULL; } } else{ if(NULL == temp->next){ master_Q[*num_mas].q = point_set; master_Q[*num_mas].parent = parent; master_Q[*num_mas].valid = true; master_Q[*num_mas].level = max_level; num_mas[0] = num_mas[0]+1; } pa = temp; temp = temp->next; } } if((*num_mas) > 1){ List *temp2 = master_Q[(*num_mas)-1].q; while(temp2){ List* temp3 = master_Q[(*num_mas)-2].q; master_Q[(*num_mas)-2].q = temp2; if((master_Q[(*num_mas)-1].parent)->p_index != (master_Q[(*num_mas)-2].parent)->p_index){ temp2->dist_index = temp2->dist_index - 1; } temp2 = temp2->next; master_Q[(*num_mas)-2].q->next = temp3; } num_mas[0] = num_mas[0]-1; } point_set = master_Q[(*num_mas)-1].q; temp = point_set; pa = point_set; parent = master_Q[(*num_mas)-1].parent; max_level = master_Q[(*num_mas)-1].level; if(master_Q[(*num_mas)-1].max) if( max_level > ((int) (ceilf(il2 * log(master_Q[(*num_mas)-1].max)))) +1) max_level = ((int) (ceilf(il2 * log(master_Q[(*num_mas)-1].max)))) +1; num_mas[0] = num_mas[0]-1; } }while(*num_mas > 0);

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• python multiprocess update dictionary synchronously

  - by user1050325

  I am trying to update one common dictionary through multiple processes. Could you please help me find out what is the problem with this code? I get the following output: inside function {1: 1, 2: -1} comes here inside function {1: 0, 2: 2} comes here {1: 0, 2: -1} Thanks. from multiprocessing import Lock, Process, Manager l= Lock() def computeCopyNum(test,val): l.acquire() test[val]=val print "inside function" print test l.release() return a=dict({1: 0, 2: -1}) procs=list() for i in range(1,3): p = Process(target=computeCopyNum, args=(a,i)) procs.append(p) p.start() for p in procs: p.join() print "comes here" print a

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• What is the "task" in twitter Storm parallelism

  - by John Wang

  I'm trying to learn twitter storm by following the great article "Understanding the parallelism of a Storm topology" However I'm a bit confused by the concept of "task". Is a task an running instance of the component(spout or bolt) ? A executor having multiple tasks actually is saying the same component is executed for multiple times by the executor, am I correct ? Moreover in a general parallelism sense, Storm will spawn a dedicated thread(executor) for a spout or bolt, but what is contributed to the parallelism by an executor(thread) having multiple tasks ? I think having multiple tasks in a thread, since a thread executes sequentially, only make the thread a kind of "cached" resource, which avoids spawning new thread for next task run. Am I correct? I may clear those confusion by myself after taking more time to investigate, but you know, we both love stackoverflow ;-) Thanks in advance.

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• MongoDB: What's the point of using MapReduce without parallelism?

  - by netvope

  Quoting http://www.mongodb.org/display/DOCS/MapReduce#MapReduce-Parallelism As of right now, MapReduce jobs on a single mongod process are single threaded Without parallelism, what are the benefits of MapReduce compared to simpler or more traditional methods for queries and data aggregation? To avoid confusion: the question is NOT "what are the benefits of document-oriented DB over traditional relational DB"

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• What's the status of multicore programming in Haskell?

  - by Don Stewart

  What's the status of multicore programming in Haskell? What projects, tools, and libraries are available now? What experience reports have there been?

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• How to printf a time_t variable as a floating point number?

  - by soneangel

  Hi guys, I'm using a time_t variable in C (openMP enviroment) to keep cpu execution time...I define a float value sum_tot_time to sum time for all cpu's...I mean sum_tot_time is the sum of cpu's time_t values. The problem is that printing the value sum_tot_time it appear as an integer or long, by the way without its decimal part! I tried in these ways: to printf sum_tot_time as a double being a double value to printf sum_tot_time as float being a float value to printf sum_tot_time as double being a time_t value to printf sum_tot_time as float being a time_t value Please help me!!

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• Erlang message loops

  - by Roger Alsing

  How does message loops in erlang work, are they sync when it comes to processing messages? As far as I understand, the loop will start by "receive"ing a message and then perform something and hit another iteration of the loop. So that has to be sync? right? If multiple clients send messages to the same message loop, then all those messages are queued and performed one after another, or? To process multiple messages in parallell, you would have to spawn multiple message loops in different processes, right? Or did I misunderstand all of it?

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• help me understand cuda

  - by scatman

  i am having some troubles understanding threads in NVIDIA gpu architecture with cuda. please could anybody clarify these info: an 8800 gpu has 16 SMs with 8 SPs each. so we have 128 SPs. i was viewing stanford's video presentation and it was saying that every SP is capable of running 96 threads cuncurrently. does this mean that it (SP) can run 96/32=3 warps concurrently? moreover, since every SP can run 96 threads and we have 8 SPs in every SM. does this mean that every SM can run 96*8=768 threads concurrently?? but if every SM can run a single Block at a time, and the maximum number of threads in a block is 512, so what is the purpose of running 768 threads concurrently and have a max of 512 threads? a more general question is:how are blocks,threads,and warps distributed to SMs and SPs? i read that every SM gets a single block to execute at a time and threads in a block is divided into warps (32 threads), and SPs execute warps.

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• Subdomain forwarding using .htaccess

  - by RJ

  I want to redirect a praticular subdomain to the main domain http(s)://dl.example.com/par1/par2 to http(s)://www.example.com/par1/par2 How to achieve the above using .htaccess Why i want to do this: Whenever any user download a file from my server, if the file is huge , then user cannot do any other operation until the file is downloaded completely...so the solution that i have thought is to forward the download request through subdomain so that the browser may continue with rest of the operation. Thanks

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• How do I make an already written concurrent program run on a GPU array?

  - by memius

  I have a neural network written in Erlang, and I just bought a GeForce GTX 260 card with a 240 core GPU on it. Is it trivial to use CUDA as glue to run this on the graphics card?

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• MPI Large Data all to all transfer

  - by csslayer

  My application of MPI has some process that generate some large data. Say we have N+1 process (one for master control, others are workers), each of worker processes generate large data, which is now simply write to normal file, named file1, file2, ..., fileN. The size of each file may be quite different. Now I need to send all fileM to rank M process to do the next job, So it's just like all to all data transfer. My problem is how should I use MPI API to send these files efficiently? I used to use windows share folder to transfer these before, but I think it's not a good idea. I have think about MPI_file and MPI_All_to_all, but these functions seems not to be so suitable for my case. Simple MPI_Send and MPI_Recv seems hard to be used because every process need to transfer large data, and I don't want to use distributed file system for now.

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• add uchar values in ushort array with sse2 or sse3

  - by pompolus

  i have an unsigned short dst[16][16] matrix and a larger unsigned char src[m][n] matrix. Now i have to access in the src matrix and add a 16x16 submatrix to dst, using sse2 or ss3. In a my older implementation, I was sure that my summed values ??were never greater than 256, so i could do this: for (int row = 0; row < 16; ++row) { __m128i subMat = _mm_lddqu_si128(reinterpret_cast<const __m128i*>(src)); dst[row] = _mm_add_epi8(dst[row], subMat); src += W; // Step to next row i need to add } where W is an offset to reach the desired rows. This code works, but now my values in src are larger and summed could be greater than 256, so i need to store them as ushort. i've tried this: for (int row = 0; row < 16; ++row) { __m128i subMat = _mm_lddqu_si128(reinterpret_cast<const __m128i*>(src)); dst[row] = _mm_add_epi16(dst[row], subMat); src += W; // Step to next row i need to add } but it doesn't work. I'm not so good with sse, so any help will be appreciated.

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• Windows Azure: Parallelization of the code

  - by veda

  I have some matrix multiplication operation. I want to parallelize the execution of those operations through multiple processors.. This can be done on high performance computing cluster using MPI (Message Passing Interface). Like wise, can I do some parallelization in the cloud using multiple worker roles. Is there any means for doing that.

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• How can i connect two or more machines via tcp cable to form a network grid?

  - by Gath

  How can i connect two or more machines to form a network grid and how can i distribute work load to the two machines? What operating systems do i need to run on the machines, and what application should i use to manage the load balancing? NB: I read somewhere that google uses cheap machines to perform this fete, how do they connect two network cards( 'Teaming' ) and distribute load across the machines? Good practical examples would serve me good, with actual code samples. Pointers to some good site i might read this stuff will be highly appreciated.

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• Improve performance writing 10 million records to text file using windows service

  - by user1039583

  I'm fetching more than 10 millions of records from database and writing to a text file. It takes hours of time to complete this operation. Is there any option to use TPL features here? It would be great if someone could get me started implementing this with the TPL. using (FileStream fStream = new FileStream("d:\\file.txt", FileMode.OpenOrCreate, FileAccess.ReadWrite)) { BufferedStream bStream = new BufferedStream(fStream); TextWriter writer = new StreamWriter(bStream); for (int i = 0; i < 100000000; i++) { writer.WriteLine(i); } bStream.Flush(); writer.Flush(); // empty buffer; fStream.Flush(); }

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• Setting the cores to use in Parallelism

  - by Ben

  Hi, I have a feeling the answer to this is no, but using .Net 4.0's Parallelism, can you set the amount of cores on which to run i.e. if your running a Quad Core, can you set your Application to only use 2 of them? Thanks

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• Executing functions parallelly in PHP

  - by binaryLV

  Hi! Can PHP call a function and don't wait for it to return? So something like this: function callback($pause, $arg) { sleep($pause); echo $arg, "\n"; } header('Content-Type: text/plain'); fast_call_user_func_array('callback', array(3, 'three')); fast_call_user_func_array('callback', array(2, 'two')); fast_call_user_func_array('callback', array(1, 'one')); would output one (after 1 second) two (after 2 seconds) three (after 3 seconds) rather than three (after 3 seconds) two (after 3 + 2 = 5 seconds) one (after 3 + 2 + 1 = 6 seconds) Main script is intended to be run as a permanent process (TCP server). callback() function would receive data from client, execute external PHP script and then do something based on other arguments that are passed to callback(). The problem is that main script must not wait for external PHP script to finish. Result of external script is important, so exec('php -f file.php &') is not an option.

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• How can I merge two Linq IEnumerable<T> queries without running them?

  - by makerofthings7

  How do I merge a List<T> of TPL-based tasks for later execution? public async IEnumerable<Task<string>> CreateTasks(){ /* stuff*/ } My assumption is .Concat() but that doesn't seem to work: void MainTestApp() // Full sample available upon request. { List<string> nothingList = new List<string>(); nothingList.Add("whatever"); cts = new CancellationTokenSource(); delayedExecution = from str in nothingList select AccessTheWebAsync("", cts.Token); delayedExecution2 = from str in nothingList select AccessTheWebAsync("1", cts.Token); delayedExecution = delayedExecution.Concat(delayedExecution2); } /// SNIP async Task AccessTheWebAsync(string nothing, CancellationToken ct) { // return a Task } I want to make sure that this won't spawn any task or evaluate anything. In fact, I suppose I'm asking "what logically executes an IQueryable to something that returns data"? Background Since I'm doing recursion and I don't want to execute this until the correct time, what is the correct way to merge the results if called multiple times? If it matters I'm thinking of running this command to launch all the tasks var AllRunningDataTasks = results.ToList(); followed by this code: while (AllRunningDataTasks.Count > 0) { // Identify the first task that completes. Task<TableResult> firstFinishedTask = await Task.WhenAny(AllRunningDataTasks); // ***Remove the selected task from the list so that you don't // process it more than once. AllRunningDataTasks.Remove(firstFinishedTask); // TODO: Await the completed task. var taskOfTableResult = await firstFinishedTask; // Todo: (doen't work) TrustState thisState = (TrustState)firstFinishedTask.AsyncState; // TODO: Update the concurrent dictionary with data // thisState.QueryStartPoint + thisState.ThingToSearchFor Interlocked.Decrement(ref thisState.RunningDirectQueries); Interlocked.Increment(ref thisState.CompletedDirectQueries); if (thisState.RunningDirectQueries == 0) { thisState.TimeCompleted = DateTime.UtcNow; } }

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• MPI Odd/Even Compare-Split Deadlock

  - by erebel55

  I'm trying to write an MPI version of a program that runs an odd/even compare-split operation on n randomly generated elements. Process 0 should generated the elements and send nlocal of them to the other processes, (keeping the first nlocal for itself). From here, process 0 should print out it's results after running the CompareSplit algorithm. Then, receive the results from the other processes run of the algorithm. Finally, print out the results that it has just received. I have a large chunk of this already done, but I'm getting a deadlock that I can't seem to fix. I would greatly appreciate any hints that people could give me. Here is my code http://pastie.org/3742474 Right now I'm pretty sure that the deadlock is coming from the Send/Recv at lines 134 and 151. I've tried changing the Send to use "tag" instead of myrank for the tag parameter..but when I did that I just keep getting a "MPI_ERR_TAG: invalid tag" for some reason. Obviously I would also run the algorithm within the processors 0 but I took that part out for now, until I figure out what is going wrong. Any help is appreciated.

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• Parallelizing a serial algorithm

  - by user643813

  Hej folks, I am working on porting a Text mining/Natural language application from single-core to a Map-Reduce style system. One of the steps involves a while loop similar to this: Queue<Element>; while (!queue.empty()) { Element e = queue.next(); Set<Element> result = calculateResultSet(e); if (!result.empty()) { queue.addAll(result); } } Each iteration depends on the result of the one before (kind of). There is no way of determining the number of iterations this loop will have to perform. Is there a way of parallelizing a serial algorithm such as this one? I am trying to think of a feedback mechanism, that is able to provide its own input, but how would one go about parallelizing it? Thanks for any help/remarks

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• Can a Perl subroutine return data but keep processing?

  - by Perl QuestionAsker

  Is there any way to have a subroutine send data back while still processing? For instance (this example used simply to illustrate) - a subroutine reads a file. While it is reading through the file, if some condition is met, then "return" that line and keep processing. I know there are those that will answer - why would you want to do that? and why don't you just ...?, but I really would like to know if this is possible. Thank you so much in advance.

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• how to do thread in matlab?

  - by hai

  how to do thread in matlab? i want to run one function on two variables simulatniosly how to do it?

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• Simple C++ container class that is thread-safe for writing

  - by conradlee

  I am writing a multi-threaded program using OpenMP in C++. At one point my program forks into many threads, each of which need to add "jobs" to some container that keeps track of all added jobs. Each job can just be a pointer to some object. Basically, I just need the add pointers to some container from several threads at the same time. Is there a simple solution that performs well? After some googling, I found that STL containers are not thread-safe. Some stackoverflow threads address this question, but none that forms a consensus on a simple solution.

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