openmp

Parallelizing recursion in a for-loop using readdir

由 二次信任 提交于 2020-05-08 19:47:17
问题 I'd like to parallelize a C-program which recursively calculates the size of a directory and its sub-directories, using OpenMP and C. My issue is, that when I get into a directory using opendir , and I iterate through the sub-directories using readdir I can only access them one by one until I've reached the last sub-directory. It all works well sequentially. When parallelizing the program, however, I think it would make sense to split the number of sub-directories in half (or even smaller

OpenMp: Best way to create an array with size of the number of threads

由 半城伤御伤魂 提交于 2020-04-30 07:11:08
问题 specific i have to calculate pi parallel with OpenMp. I am just allowed using #omp parallel. So i wanted to create an array with the size of the number of processes and then calculating partially the sum parallel and then calculating the sums together. But it's unfortunately impossible to get the number of threads before the parallel version. So is the best way to create a very large array and initializing it with 0.0 and then calculating everything together or is there a better way? I would

使用openmp进行并行编程

由 送分小仙女□ 提交于 2020-04-29 09:02:10
预处理指令pragma 在系统中加入预处理器指令一般是用来允许不是基本c语言规范部分的行为。不支持pragma的编译器会忽略pragma指令提示的那些语句，这样就允许使用pragma的程序在不支持它们的平台上运行。 第一个程序：hello #include <stdio.h> #include <stdlib.h> #include <omp.h> void Hello(void); // Thread function int main(int argc, char* argv[]) { // Get number of threads from command line int thread_count = strtol(argv[1], NULL, 10); #pragma omp parallel num_threads(thread_count) Hello(); return 0; } void Hello(void) { int my_rank = omp_get_thread_num(); int thread_count = omp_get_num_threads(); printf("Hello from thread %d of %dnn\n", my_rank, thread_count); } Hello例子的分析： 最基本的并行原语

How to generate uniformly distributed random numbers between 0 and 1 in a C code using OpenMP?

由 坚强是说给别人听的谎言 提交于 2020-04-16 05:47:20
问题 I am trying to write an OpenMP code in which each thread will work on big arrays of uniformly distributed random numbers between 0 and 1. Each thread needs to have different and independent random number distributions. In addition, the random number distributions need to be different every time the code is called. This is what I am using right now. Does this always guarantee each thread has its own/different random number sequences? Will the sequences be different every time the code is

How to generate uniformly distributed random numbers between 0 and 1 in a C code using OpenMP?

由 白昼怎懂夜的黑 提交于 2020-04-16 05:47:10
问题 I am trying to write an OpenMP code in which each thread will work on big arrays of uniformly distributed random numbers between 0 and 1. Each thread needs to have different and independent random number distributions. In addition, the random number distributions need to be different every time the code is called. This is what I am using right now. Does this always guarantee each thread has its own/different random number sequences? Will the sequences be different every time the code is

Scaling issues with OpenMP

由 删除回忆录丶 提交于 2020-04-16 05:17:12
问题 I have written a code for a special type of 3D CFD Simulation, the Lattice-Boltzmann Method (quite similar to a code supplied with the Book "The Lattice Boltzmann Method" by Timm Krüger et alii). Multithreading the program with OpenMP I have experienced issues that I can't quite understand: The results prove to be strongly dependent on the overall domain size. The basic principle is that each cell of a 3D domain gets assigned certain values for 19 distribution functions (0-18) in discrete

Scaling issues with OpenMP

由 情到浓时终转凉″ 提交于 2020-04-16 05:17:03
问题 I have written a code for a special type of 3D CFD Simulation, the Lattice-Boltzmann Method (quite similar to a code supplied with the Book "The Lattice Boltzmann Method" by Timm Krüger et alii). Multithreading the program with OpenMP I have experienced issues that I can't quite understand: The results prove to be strongly dependent on the overall domain size. The basic principle is that each cell of a 3D domain gets assigned certain values for 19 distribution functions (0-18) in discrete

LLVM / Clang 8 Compilation of OpenMP Code in Windows

由 淺唱寂寞╮ 提交于 2020-04-15 02:57:48
问题 I'm using the Windows version of Clang (LLVM) 8 under Windows. I'm compiling a code which uses OpenMP. Under the lib folder of Clang there are 2 files which are OpenMP related: libomp.lib . libiomp5md.dll . My questions are: When I compile the code I use the flags -Xclang -fopenmp for the compiler. In in GCC and ICC using the flags tell the compiler to link the OpenMP library automatically. What about Clang? Does it do it automatically or must I link with libomp.lib manually? Is there a way

LLVM / Clang 8 Compilation of OpenMP Code in Windows

由 戏子无情 提交于 2020-04-15 02:57:37
问题 I'm using the Windows version of Clang (LLVM) 8 under Windows. I'm compiling a code which uses OpenMP. Under the lib folder of Clang there are 2 files which are OpenMP related: libomp.lib . libiomp5md.dll . My questions are: When I compile the code I use the flags -Xclang -fopenmp for the compiler. In in GCC and ICC using the flags tell the compiler to link the OpenMP library automatically. What about Clang? Does it do it automatically or must I link with libomp.lib manually? Is there a way

LLVM / Clang 8 Compilation of OpenMP Code in Windows

由 我怕爱的太早我们不能终老 提交于 2020-04-15 02:57:09
问题 I'm using the Windows version of Clang (LLVM) 8 under Windows. I'm compiling a code which uses OpenMP. Under the lib folder of Clang there are 2 files which are OpenMP related: libomp.lib . libiomp5md.dll . My questions are: When I compile the code I use the flags -Xclang -fopenmp for the compiler. In in GCC and ICC using the flags tell the compiler to link the OpenMP library automatically. What about Clang? Does it do it automatically or must I link with libomp.lib manually? Is there a way
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