openmp

I have a fairly complex program that runs into strange behavior when build with OpenMP in MSVC 2010 Debug mode. I have tried my best to construct the following minimal working example (though it is not really minimal) which minic the structure of the real program. #include <vector> #include <cassert> // A class take points to the whole collection and a position Only allow access // to the elements at that posiiton. It provide read-only access to query some // information about the whole collection class Element { public : Element (int i, std::vector<double> *src) : i_(i), src_(src) {} int i ()

可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 问题: I'm implementing Boruvka's algorithm in C++ to find minimum spanning tree for a graph. This algorithm finds a minimum-weight edge for each supervertex (a supervertex is a connected component, it is simply a vertex in the first iteration) and adds them into the MST. Once an edge is added, we update the connected components and repeat the find-min-edge, and merge-supervertices process, until all the vertices in the graph are in one connected component. Since find-min-edge for each supervertex can be done in parallel, I want to use OpenMP to do

可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 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 OMP_NESTED : FALSE KMP_STATSFILE : guide.gvs KMP

可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 问题: Given the following code... for (size_t i = 0; i < clusters.size(); ++i) { const std::set<int>& cluster = clusters[i]; // ... expensive calculations ... for (int j : cluster) velocity[j] += f(j); } ...which I would like to run on multiple CPUs/cores. The function f does not use velocity . A simple #pragma omp parallel for before the first for loop will produce unpredictable/wrong results, because the std::vector<T> velocity is modified in the inner loop. Multiple threads may access and (try to) modify the same element of velocity at the same

可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 由 翻译 强力驱动 问题: I have a simple program that I am using for physics simulation. I want to know how to implement a certain threading paradigm in OpenMP. int main () { #define steps ( 100000 ) for ( int t = 0 ; t < steps ; t ++) { firstParallelLoop (); secondParallelLoop (); if (!( t % 100 )) { checkpoint (); } } } void firstParallelLoop () { // In another file.c #pragma omp parallel for for ( int i = 0 ; i < sizeOfSim ; i ++) { //Some atomic floating point ops. } } Formerly, I was using pthreads and got a 1.7 speedup on my dualcore laptop. I can't

可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 问题: I've gotten stuck writing some parallel c code using OpenMP for a concurrency course. Heres a snippet #include <stdio.h> #include <time.h> #include <math.h> #define FALSE 0 #define TRUE 1 int count_primes_0(int); int count_primes_1(int); int count_primes_2(int); int main(int argc, char *argv[]){ int n; if (argc != 2){ printf("Incorrect Invocation, use: \nq1 N"); return 0; } else { n = atoi(argv[1]); } if (n < 0){ printf("N cannot be negative"); return 0; } printf("N = %d\n", n); //omp_set_num_threads(1); time_it(count_primes_0, n, "Method 0"

可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 问题: 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