使用 openmp 并行执行函数 [英] Execute functions in parallel using openmp
问题描述
我对几个独立函数进行了一系列调用.
I have a series of calls to few independent functions.
func1(arg);
func2(arg);
func3(arg);
我想并行执行它们,而不是串行执行它们.我目前正在使用
Instead of executing them serially, I want to execute them in parallel. I am currently using
#pragma omp parallel
{
func1(arg);
func2(arg);
func3(arg)
}
我尝试的其他方法是使用 switch case,然后并行执行它以将任务拆分到不同的线程,例如
Other ways I'm trying is using a switch case and then executing this in parallel to split the task to different threads like
function(arg, value)
{
switch(value)
{
case 1: // code of func1
case 2: // code of func2
case 3 :// code of func3
}
}
#pragma omp parallel for
for(j=0; j<3; j++)
function(arg, j);
我的问题是这些方法中的任何一个都不比对函数的顺序调用更好.我如何并行化对这些函数的调用.
My question is either of these methods is not better than a sequential calls to functions. How do I parallelize the calls to these functions.
谢谢,K
推荐答案
您正在寻找 OpenMP 任务,在 OpenMP 3 中添加:
You're looking for OpenMP tasks, added in OpenMP 3:
#include <stdio.h>
#include <omp.h>
void func1(int arg) {
int tid = omp_get_thread_num();
printf("Thread %d in func1: got arg %d\n", tid, arg);
}
void func2(int arg) {
int tid = omp_get_thread_num();
printf("Thread %d in func2: got arg %d\n", tid, arg);
}
void func3(int arg) {
int tid = omp_get_thread_num();
printf("Thread %d in func3: got arg %d\n", tid, arg);
}
int main(int argc, char **argv) {
int arg=173;
#pragma omp parallel default(none) shared(arg)
#pragma omp single
{
#pragma omp task
func1(arg);
#pragma omp task
func2(arg);
#pragma omp task
func3(arg);
#pragma omp taskwait
/* if you have something that needs all the results above
* but needs to be in the parallel reason it would go here;
* otherwise the task wait is not needed */
}
return 0;
}
跑步给予:
$ export OMP_NUM_THREADS=3
$ ./tasks
Thread 1 in func3: got arg 173
Thread 0 in func2: got arg 173
Thread 2 in func1: got arg 173
如果由于某种原因(Visual Studio)您无法使用 OpenMP 2,您可以使用部分,这些部分不太灵活但在这里工作正常:
If for some reason (Visual Studio) you're stuck using OpenMP 2, you can use sections, which are less flexible but work fine here:
int main(int argc, char **argv) {
int arg=173;
#pragma omp parallel sections default(none) shared(arg)
{
func1(arg);
#pragma omp section
func2(arg);
#pragma omp section
func3(arg);
}
return 0;
}
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