OpenMP计算实例计算pi.pptVIP

#include omp.h #include stdio.h #define N 1000 int main(){ int I, tid; float a[N], b[N], c[N],d[N]; /* vectors initializations */ for (i=0; i N; i++) a[i] = b[i] = i * 1.0; 嵌入上页那段代码； } 你可以尝试一下编译此代码 For Loop 编译制导语句 for语句指定紧随它的循环语句必须由线程组并行执行； #pragma omp for for ( i = 0; …. ) 分割for循环的方法可由一个附加的调度 “schedule” 语句. Example schedule (static, chunk_size) 将for循环按chunk_size所指明的大小进行分割，且以轮转的方式分给线程(静态). For 循环必须是简单规范的形式 schedule子句描述如何将循环的迭代划分给线程组中的线程 schedule (static, chunk_size),循环被静态划分为大小为chunk的块，以轮转的方式分给线程，如果没有指定chunk大小，迭代会尽可能的平均分配给每个线程 schedule (dynamic, chunk_size),循环被动态划分为大小为chunk的块，动态分配给线程(当有进程空闲就分配一块)，如果没有指定chunk大小就默认为1 3. schedule (guided,chunk_size) 4. schedule (runtime) Example #pragma omp parallel shared(a,b,c,nthreads,chunk) private(i,tid) { tid = omp_get_thread_num(); if (tid == 0) { nthreads = omp_get_num_threads(); printf(Number of threads = %d\n, nthreads); } printf(Thread %d starting...\n,tid); ? #pragma omp for schedule(dynamic,chunk) for (i=0; iN; i++) { c[i] = a[i] + b[i]; printf(Thread %d: c[%d]= %f\n,tid,i,c[i]); } ? } /* end of parallel section */ For loop Executed by one thread Single编译制导语句 single编译制导语句指定内部代码只有线程组中的一个线程执行。线程组中没有执行single语句的线程会一直等待代码块的结束，使用nowait子句除外 #pragma omp single structured block Combined Parallel Work-sharing Constructs 组合的并行共享任务结构 If a parallel directive is followed by a single for directive, it can be combined with similar effects. Parallel for编译制导语句表明一个并行域包含一个独立的for语句 #pragma omp parallel for for loop #include omp.h #define N 1000 #define CHUNKSIZE 100 int main () { int i, chunk; float a[N], b[N], c[N]; /* Some initializations */ for (i=0; i N; i++) a[i] = b[i] = i * 1.0; chunk = CHUNKSIZE; #pragma omp parallel for shared(a,b,c,chunk) private(i) schedule(static,chunk) for (i=0; i n; i++) c[i] = a[i] + b[i]; } Parallel for举例 parallel sections编译制导语句 parallel sections编译制导语句表明一个并行域包含单独的一个sections语句