barrier

MPI_Barrier not working inside a loop

由 与世无争的帅哥 提交于 2019-12-12 17:08:09
问题 I have running some tests on the MPI functions to understand how it works and have got a weird result with the MPI_Barrier: it does what everyone would expect if I use it in code like int main(int argc, char *argv[]) { <some code> MPI_Barrier(MPI_COMM_WORLD); <more code> MPI_Barrier(MPI_COMM_WORLD); <...> } but when I call it from inside a loop i get random results. To be specific, I have the following test code: #include "mpi.h" #include <stdio.h> int main(int argc, char *argv[]) { int i, rb

MPI_BARRIER not working

由 99封情书 提交于 2019-12-12 06:26:23
问题 Why is here the barrier not working? If I use it, the program gets blocked, otherwise I get the output in a weird order: Number of worker tasks = 4 sending 1-th element q=0.011000 to task 1 sending 2-th element q=0.012000 to task 2 received 1-th element q=0.011000 in task 1 processed 1-th element q=6.105000 in task 1 sending 3-th element q=0.013000 to task 3 received 2-th element q=0.012000 in task 2 processed 2-th element q=13.320000 in task 2 sending 4-th element q=0.014000 to task 4

Waiting for OpenMP task completion at implicit barriers?

由 雨燕双飞 提交于 2019-12-11 05:53:00
问题 If I create a bunch of OpenMP tasks and do not use taskwait , where does the program wait for that tasks completion? Consider the following example: #pragma omp parallel { #pragma omp single { for (int i = 0; i < 1000; i++) { #pragma omp task ... // e.g., call some independent function } // no taskwait here } // all the tasks completed now? } Does the program wait for task completion at the implicit barrier at the end of the single block? I assume so, but cannot find any information about

Why does MPI_Barrier cause a segmentation fault in C++

由 筅森魡賤 提交于 2019-12-10 14:42:17
问题 I have reduced my program to the following example: #include <mpi.h> int main(int argc, char * argv[]) { int rank, size; MPI_Init(&argc, &argv); MPI_Comm_rank(MPI_COMM_WORLD, &rank); MPI_Comm_size(MPI_COMM_WORLD, &size); MPI_Barrier(MPI_COMM_WORLD); MPI_Finalize(); return 0; } I compile and run the code, and get the following result: My-MacBook-Pro-2:xCode_TrapSim user$ mpicxx -g -O0 -Wall barrierTest.cpp -o barrierTestExec My-MacBook-Pro-2:xCode_TrapSim user$ mpiexec -n 2 ./barrierTestExec =

MPI code does not work with 2 nodes, but with 1

由 给你一囗甜甜゛ 提交于 2019-12-10 11:19:35
问题 Super EDIT: Adding the broadcast step, will result in ncols to get printed by the two processes by the master node (from which I can check the output). But why? I mean, all variables that are broadcast have already a value in the line of their declaration!!! (off-topic image). I have some code based on this example. I checked that cluster configuration is OK, with this simple program, which also printed the IP of the machine that it would run onto: int main (int argc, char *argv[]) { int rank

Synchronize threads for pthread_cond_broadcast call

由 允我心安 提交于 2019-12-10 10:23:06
问题 I have a simple application with a "manager" thread that spawns ten simple "worker" threads. I want all of the "worker" threads to block on the same condition variable (ie: condvar), and I want to manually signal all ten threads to wake up at the same time with a pthread_cond_broadcast call. In the case of my application, it is possible for threads to suffer an error condition and terminate early, so it is possible that not all ten threads make it to the synchronization point. One simple

Modification to “Implementing an N process barrier using semaphores”

由 喜你入骨 提交于 2019-12-07 17:36:59
问题 Recently I see this problem which is pretty similar to First reader/writer problem. Implementing an N process barrier using semaphores I am trying to modify it to made sure that it can be reuse and work correctly. n = the number of threads count = 0 mutex = Semaphore(1) barrier = Semaphore(0) mutex.wait() count = count + 1 if (count == n){ barrier.signal()} mutex.signal() barrier.wait() mutex.wait() count=count-1 barrier.signal() if(count==0){ barrier.wait()} mutex.signal() Is this correct? I

Barrier operations in NSOperationQueue

由 筅森魡賤 提交于 2019-12-07 02:03:58
问题 How can we implement dispatch_barrier_async 's equivalent behavior using NSOperationQueue or any user-defined data-structure based on NSOperationQueue ? The requirement is, whenever a barrier operation is submitted it should wait until all non-barrier operations submitted earlier finish their execution and blocks other operations submitted after that. Non-barrier operations should be able to perform concurrently. Barrier operations should execute serially. NB: Not using GCD ,as it doesn't

MPI code does not work with 2 nodes, but with 1

由 余生颓废 提交于 2019-12-06 11:15:14
Super EDIT: Adding the broadcast step, will result in ncols to get printed by the two processes by the master node (from which I can check the output). But why? I mean, all variables that are broadcast have already a value in the line of their declaration!!! (off-topic image ). I have some code based on this example . I checked that cluster configuration is OK, with this simple program, which also printed the IP of the machine that it would run onto: int main (int argc, char *argv[]) { int rank, size; MPI_Init (&argc, &argv); /* starts MPI */ MPI_Comm_rank (MPI_COMM_WORLD, &rank); /* get

Modification to “Implementing an N process barrier using semaphores”

由 南笙酒味 提交于 2019-12-05 20:34:32
Recently I see this problem which is pretty similar to First reader/writer problem. Implementing an N process barrier using semaphores I am trying to modify it to made sure that it can be reuse and work correctly. n = the number of threads count = 0 mutex = Semaphore(1) barrier = Semaphore(0) mutex.wait() count = count + 1 if (count == n){ barrier.signal()} mutex.signal() barrier.wait() mutex.wait() count=count-1 barrier.signal() if(count==0){ barrier.wait()} mutex.signal() Is this correct? I'm wondering if there exist some mistakes I didn't detect. Your pseudocode correctly returns barrier
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