OpenMP(Open Multi-Processing)是一套用于并行编程的API,而#pragma omp指令就是用来指导编译器进行OpenMP并行化的。通过在循环、函数等代码块前加上#pragma omp,可以让编译器自动并行化该代码块,充分利用多核处理器的性能。 复制 #pragma omp parallelforfor(int i=0;i<n;++i){// 并行化的代码} 1. 2. 3....
8 ParallelDirective并行域结构 #pragmaompparallel structured_block //语句形成的结构块,对每个线程执行结构块 它将创建多线程,每个线程执行特定的 structured_block,structured_block可以是一条语句也可以是用 {...}创建的复合语句,但必须只有一个入口,一个出口。 在该结构结束处隐含一个barrier. 该parallel命令就相...
int a[N]; #pragma omp target map(to: N) map(tofrom: a) #pragma omp parallel for simd for (i=0, i<N, i++) { a[i] = N; } #pragma omp end parallel for simd #pragma omp end target In this example, theomp parallel for simddirective distributes the iterations of the loop ac...
Usage The omp barrier directive must appear within a block or compound statement. For example: if (x!=0) { #pragma omp barrier /* valid usage */ } if (x!=0) #pragma omp barrier /* invalid usage */Parent topic: Pragma directives for parallel processing ...
Usage Theomp barrierdirective must appear within a block or compound statement. For example: if (x!=0) { #pragma omp barrier /* valid usage */ } if (x!=0) #pragma omp barrier /* invalid usage */
An iteration of a loop must not execute the sameomp ordereddirective more than once. An iteration of a loop must not execute more than one distinctomp ordereddirective. #pragma omp parallel for Description Theomp parallel fordirective effectively combines theomp parallelandomp fordirectives. This ...
Example 1 The following SIMD construct enables the execution of multiple iterations of the associated loop concurrently by using SIMD instructions. #pragma omp simd { for (i=0; i<N; i++) { a[i] = a[i] + b[i] * c[i]; }
#pragma omp barrier Purpose Theomp barrierdirective identifies a synchronization point at which threads in a parallel region will not execute beyond theomp barrieruntil all other threads in the team complete all explicit tasks in the region.
The value ofint_expis an integer expression that specifies the number of threads to use for the parallel region. If dynamic adjustment of the number of threads is also enabled, thenint_expspecifies the maximum number of threads to be used. ...
Example 3: Atomic capture extern int x[10]; extern int f(int); int temp[10], i; for(i = 0; i < 10; i++) { #pragma omp atomic capture temp[i] = x[f(i)]++; #pragma omp atomic capture { temp[i] = x[f(i)]; //the two occurences of x[f(i)] must evaluate to the...