Shulou(Shulou.com)06/02 Report--

This article focuses on "what is the method of OpenMP parallel programming". Interested friends may wish to have a look at it. The method introduced in this paper is simple, fast and practical. Let's let the editor take you to learn "what is the OpenMP parallel programming method"?

In the properties dialog box of the project in VC8.0, under "configuration Properties" in the left box, in the "language" page under "C _ OpenMP +", change the OpenMP support to "Yes / (OpenMP)" to support OpenMP.

Let's first look at a simple program that uses OpenMP.

Int main (int argc, char* argv []) {# pragma omp parallel for for (int I = 0; I < 10; iPlus +) {printf ("I =% DBO", I);} return 0;} print the following result after execution of this program: I = 0 I = 5 I = 1 I = 6 I = 2 I = 7 I = 3 I = 8 I = 4 I = 9

You can see that the contents of the for loop statement are executed in parallel. (the print result may be different for each run)

To make it clear here, the statement # pragma omp parallel for is used to specify that the subsequent for loop statements are executed in parallel, of course, the contents of the for loop must be executed in parallel, that is, each loop is independent of each other, and the latter loop does not depend on the previous loop.

The specific meaning of the statement # pragma omp parallel for and the introduction of related OpenMP instructions and functions will be put aside for the time being, as long as you know that this statement will turn the contents of the subsequent for loop into parallel execution.

I think we are most concerned about whether the efficiency will be improved after turning the statements in the for loop into parallel execution. Let's write a simple test program to test it:

Void test () {int a = 0; clock_t T1 = clock (); for (int I = 0; I < 100000000; iTunes +) {a = ionome1;} clock_t T2 = clock (); printf ("Time =% dZone", t2-t1);} int main (int argc, char* argv []) {clock_t T1 = clock () # pragma omp parallel for for (int j = 0; j < 2; clock_t +) {test ();} clock_t T2 = clock (); printf ("Total time =% dzone", t2-t1); test (); return 0;} in the test () function, 100 million loops are executed, mainly to perform a long operation. In the main () function, the test () function is called in a loop only twice. Let's take a look at the running result on dual-core CPU: Time = 297 Time = 297 Total time = 297 Time = 297

You can see that the two calls to the test () function in the for loop cost 297ms, but the total print time only takes 297ms, and the test () function executed separately takes the same time as 297ms, which shows that the efficiency is doubled after using parallel computing.

At this point, I believe you have a deeper understanding of "what is the method of OpenMP parallel programming". You might as well do it in practice. Here is the website, more related content can enter the relevant channels to inquire, follow us, continue to learn!

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