openmp

问题 I am trying to parallelize a simple mandelbrot c program, yet I get this error that has to do with not including acc routine information. Also, I am not sure whether I should be copying data in and out of the parallel section. PS I am relatively new to parallel programming, so any advice with learning it would be appreciated. (Warning when compiled) PGC-S-0155-Procedures called in a compute region must have acc routine information: fwrite (mandelbrot.c: 88) PGC-S-0155-Accelerator region

问题 I got this homework: Implement an OpenMP program that generates prime numbers in a given interval. You should use the prime generation method given in the next page ( Do NOT use other method !). Your program should generate a csv le called results.csv that reports the timing results in the following format. Table needed to be output #include <stdio.h> #define N 50 main() { int prime[N] ; int j ; int k ; int n ; int quo,rem ; P1: prime[0] = 2 ; n = 3 ; j = 0 ; P2: j = j+1 ; prime[j] = n ; P3:

问题 I got this homework: Implement an OpenMP program that generates prime numbers in a given interval. You should use the prime generation method given in the next page ( Do NOT use other method !). Your program should generate a csv le called results.csv that reports the timing results in the following format. Table needed to be output #include <stdio.h> #define N 50 main() { int prime[N] ; int j ; int k ; int n ; int quo,rem ; P1: prime[0] = 2 ; n = 3 ; j = 0 ; P2: j = j+1 ; prime[j] = n ; P3:

问题 I wrote an Openmp Program, running it on a two core machine. When I changed the thread number from 1 to 2 and from 2 to 4, I couldn't get the 2x speed up. 2 threads to 4 threads, that's the hyperthreads. Hyperthreads generally can't get 2x speed up because of resources limitation. However, 1 threads to 2 threads, still can't get the 2x speed up, I feel confused about this.I searched and found the CPU affinity concept, but I can't figure out how Openmp works. When I use 2 threads, does Openmp

问题 I'm trying to get openmp to run in my program on Mavericks, however when I try to compile using the flag -fopenmp I get the following error: ld: library not found for -lgomp clang: error: linker command failed with exit code 1 (use -v to see invocation) The command I am running is: gcc myProgram.cpp -fopenmp -o myProgram Also, when I run gcc I get Clang warnings which I find to be very strange. And looking into /usr/bin/gcc it does not appear to link to Clang. Any suggestions on how to fix my

问题 I got the following problem: I have to measure the time a program needs to be executed. A scalar version of the program works fine with the code below, but when using OpenMP, it works on my PC, but not on the resource I am supposed to use. In fact: scalar program rt 34s openmp program rt 9s thats my pc (everything working) -compiled with visual studio the ressource I have to use (I think Linux, compiled with gcc): scalar program rt 9s openmp program rt 9s (but the text pops immediately

问题 I just started to use OpenMP to do parallel computing in C++. The program has a bad parallel performance. Since I don't know many multi-threading profiling tool (unlike simple gprof for single thread), I wrote a sample program to test the performance. I have a 2D matrix(N * N), with each element a 3d vector(x, y, z). I simply do a double for loop to set each value in the matrix: for (int i = 0; i < N; ++i) { for (int j = 0; j < N; ++j) { vectorStack[i][j] = VECTOR3D(1.0*i*i, 1.0*j*j, 1.0*i*j)

问题 I'm trying to parallelize a code I've written. I'm having problems performing reducitons on arrays. It all seems to work fine for smallish arrays, however when the array size goes above a certain point I either get a stack overflow error or a crash. I've tried to increased the stack size using the /F at compile time, I'm using ifort on windows, I've also tried passing set KMP_STACKSIZE=xxx the intel specific stacksize decleration. This sometimes helps and allows the code to progress further

问题 I need to run a short outer loop and a long inner loop. I would like to parallelize the latter and not the former. The reason is that there is an array that is updated after the inner loop has run. The code I am using is the following #pragma omp parallel{ for(j=0;j<3;j++){ s=0; #pragma omp for reduction(+:s) for(i=0;i<10000;i++) s+=1; A[j]=s; } } This actually hangs. The following works just fine, but I'd rather avoid the overhead of starting a new parallel region since this was preceded by

问题 I'm using OpenMP in Visual Studio 2010 to speed up loops. I wrote a very simple test to see the performance increase using OpenMP. I use omp parallel on an empty loop int time_before = clock(); #pragma omp parallel for for(i = 0; i < 4; i++){ } int time_after = clock(); std::cout << "time elapsed: " << (time_after - time_before) << " milliseconds" << std::endl; Without the omp pragma it consistently takes 0 milliseconds to complete (as expected), and with the pragma it usually takes 0 as well