高性能计算-OpenMPProgramming浅析.ppt

OpenMP Programming OpenMP Introduction OpenMP-Open Multi-Processing OpenMP is an Application Program Interface (API) Comprised of three components: Compiler directives Runtime library routines(运行库例程) Environment variables OpenMP program A program that consists of a base program, annotated with OpenMP directives and runtime library routines. base program A program written in a programming language. Three components of OpenMP Directives/pragmas Create threads Share the work amongst threads Synchronize threads Library routines external functions(外部功能) Control and query the parallel execution environment(控制和查询并行执行环境) Environment variables control the behavior of an OpenMP program Directives specifying how a compiler or assembler should process its input OpenMP directives for C/C++ are specified with the pragma preprocessing directive #pragma omp directive-name [clause[ [,] clause]...] new-line #pragma omp parallel #pragma omp for #pragma omp parallel for #pragma omp barrier Create threads/Share the work amongst threads/Synchronize threads Runtime Library a header file named omp.h omp_set_num_threads, omp_get_num_threads omp_get_max_threads, omp_get_thread_num omp_get_num_procs, omp_in_parallel omp_set_dynamic, omp_get_dynamic omp_set_nested, omp_get_nested omp_set_schedule, omp_get_schedule omp_get_thread_limit omp_set_max_active_levels omp_get_max_active_levels omp_get_level, omp_get_ancestor_thread_num omp_get_team_size, omp_get_active_level omp_in_final external functions/Control and query the parallel execution environment environment variables:control the behavior of an OpenMP program OMP_NUM_THREADS OMP_SCHEDULE OMP_DYNAMIC OMP_PROC_BIND OMP_NESTED OMP_STACKSIZE OMP_WAIT_POLICY OMP_MAX_ACTIVE_LEVELS OMP_THREAD_LIMIT The OpenMP Execution Model The OpenMP Memory Model parallel construct A set of implicit(隐含) tasks, one per thread, is generated. The code for each task is defined by the code inside the parallel construct. #pragma omp parallel [clause[ [, ]clau