openmp

问题 Is there a format of *.gvs files, used by GuideView OpenMP performance analyser? The "guide.gvs" is generated, f.e. by intel's OpenMP'ed programmes with $ export LD_PRELOAD=<path_to_icc_or_redist>/lib/libiompprof5.so $ ./openmp_parallelized_prog $ ls -l guide.gvs 回答1: It s a plain text. Here is an example of such from very short omp programme: $ cat guide.gvs *** KAI statistics library k3301 *** Begin Task 0 Environment variables: OMP_NUM_THREADS : 2 OMP_SCHEDULE : static OMP_DYNAMIC : FALSE

问题 I am very new to openMP, but am trying to write a simple program that generates the entries of matrix in parallel, namely for the N by M matrix A, let A(i,j) = i*j. A minimal example is included below: #include <stdio.h> #include <stdlib.h> #include <omp.h> int main(int argc, char **argv) { int i, j, N, M; N = 20; M = 20; int* A; A = (int*) calloc(N*M, sizeof(int)); // compute entries of A in parallel #pragma omp parallel for shared(A) for (i = 0; i < N; ++i){ for (j = 0; j < M; ++j){ A[i*M +

问题 Near the start of my c++ application, my main thread uses OMP to parallelize several for loops. After the first parallelized for loop, I see that the threads used remain in existence for the duration of the application, and are reused for subsequent OMP for loops executed from the main thread, using the command (working in CentOS 7): for i in $(pgrep myApplication); do ps -mo pid,tid,fname,user,psr -p $i;done Later in my program, I launch a boost thread from the main thread, in which I

问题 I have some code which looks a bit like this: std::random_device rd; #pragma omp parallel { std::mt19937 gen(rd()); #pragma omp for for(int i=0; i < N; i++) { /* Do stuff with random numbers from gen() */ } } I have a few questions: Is std::random_device thread safe? i.e. Is it going to do something unhelpful when several threads call it at once? Is this generally a good idea? Should I be worried about overlapping random number streams? Is there a better way to achieve what I want

问题 I would like to improve performance of our MFC application with parallel processing. Of course, I've searched OpenMP and MFC over internet. Most of posts are about struggling with integrating OpenMP into MFC app. That led this question. Is it possible to use OpenMP for a MFC application? UPDATE: It seems that Currency Runtime can do what OpenMP does for MFC. But I would like to still make sure about the question above. 回答1: I can't see any reason why MFC should stop you using openMP. Although

问题 I have been testing the code at In an OpenMP parallel code, would there be any benefit for memset to be run in parallel? and I'm observing something unexpected. My system is a single socket Xeon E5-1620 which is an Ivy Bridge processor with 4 physical cores and eight hyper-threads. I'm using Ubuntu 14.04 LTS, Linux Kernel 3.13, GCC 4.9.0, and EGLIBC 2.19. I compile with gcc -fopenmp -O3 mem.c When I run the code in the link it defaults to eight threads and gives Touch: 11830.448 MB/s Rewrite:

问题 Anyone think about it. OpenMP features to adjust cpu muscles to handle dumbbel. In my research for openmp we cannot set thread priority to execute block code with powerfull muscle. Only one way(_beginthreadex or CreateThread function with 5. parameters) to create threads with highest priority. Here some code for this issue: This is manual setting. int numberOfCore = ( execute __cpuid to obtain number of cores on your cpu ). HANDLES* hThreads = new HANDLES[ numberOfCore ]; hThreads[0] =

问题 I'm using Python 3.4.3 and OpenCV 3.0.0 to process (applying various filters to) a very large image (80,000 x 60,000) in memory and I'd like to use multiple CPU cores to improve performance. After some reading, I arrived at two possible method : 1) Use python's multiprocessing module, let each process deal with a slice of the large image and join the results after processing is done (And this probably should be performed on POSIX system?) 2) Since NumPy supports OpenMP and OpenCV uses NumPy,

问题 I have this file: A.h struct B; struct A { A(... B &b) : b(b) {} B &b; }; And B.h : #include "A.h" struct B{ ... std::vector<A> as; } And I have this omp_declare_reduction : #pragma omp declare reduction(merge : B : omp_out.as.insert(omp_out.as.end(), omp_in.as.begin(), omp_in.as.end())) However, I get this error (where A=FindAffineShapeArgs and B=Wrapper ): /usr/include/c++/5/bits/stl_algobase.h(564): error: function "FindAffineShapeArgs::operator=(const FindAffineShapeArgs &)" (declared

问题 How do I detect the number of threads in OpenMp before the parallel region starts? If I use nested parallelism the environment variable OMP_NUM_THREADS looks like 4,64 . get_nested_num_threads(); #pragma omp parallel { // starting 4 threads #pragma omp parallel { // starting 64 threads for each of the 4 } } This answer leads to my implementation of querying OMP_NUM_THREADS with the following code: #include <string.h> #include <stdlib.h> int get_nested_num_threads(){ char delimiter[] = ",";