Introductions to Parallel Programming Using OpenMP课件.ppt

OpenMP: Library routines Lock routines omp_init_lock(), omp_set_lock(), omp_unset_lock(), omp_test_lock() Runtime environment routines: Modify/Check the number of threads omp_set_num_threads(), omp_get_num_threads(), omp_get_thread_num(), omp_get_max_threads() Turn on/off nesting and dynamic mode omp_set_nested(), omp_set_dynamic(), omp_get_nested(), omp_get_dynamic() Are we in a parallel region? omp_in_parallel() How many processors in the system? omp_num_procs() OpenMP: Environment Variables OMP_NUM_THREADS bsh: export OMP_NUM_THREADS=2 csh: setenv OMP_NUM_THREADS 4 Content Overview of OpenMP Acknowledgement OpenMP constructs (5 categories) OpenMP exercises References #include omp.h main () { int nthreads, tid; /* Fork a team of threads giving them their own copies of variables */ #pragma omp parallel private(nthreads, tid) { /* Obtain thread number */ tid = omp_get_thread_num(); printf(Hello World from thread = %d\n, tid); /* Only master thread does this */ if (tid == 0) { nthreads = omp_get_num_threads(); printf(Number of threads = %d\n, nthreads); } } /* All threads join master thread and disband */ } 1. Hello World! Example Code - Pthread Creation and Termination #include pthread.h #include stdio.h #define NUM_THREADS 5 void *PrintHello(void *threadid) { printf(\n%d: Hello World!\n, threadid); pthread_exit(NULL); } int main (int argc, char *argv[]) { pthread_t threads[NUM_THREADS]; int rc, t; for(t=0; tNUM_THREADS; t++) { printf(Creating thread %d\n, t); rc = pthread_create(threads[t], NULL, PrintHello, (void *)t); if (rc) { printf(ERROR; return code from pthread_create() is %d\n, rc); exit(-1); } } pthread_exit(NULL); } PROGRAM REDUCTION INTEGER I, N REAL A(100), B(100), SUM ! Some initializations N = 100 DO I = 1, N A(I) = I *1.0 B(I) = A(I) ENDDO SUM = 0.0 !