C++ Concurrency With OpenMP OpenMP: Parallel Sections
Example
This example illustrates the basics of executing sections of code in parallel.
As OpenMP is a built-in compiler feature, it works on any supported compilers without including any libraries. You may wish to include omp.h if you want to use any of the openMP API features.
Sample Code
std::cout << "begin ";
// This pragma statement hints the compiler that the
// contents within the { } are to be executed in as
// parallel sections using openMP, the compiler will
// generate this chunk of code for parallel execution
#pragma omp parallel sections
{
// This pragma statement hints the compiler that
// this is a section that can be executed in parallel
// with other section, a single section will be executed
// by a single thread.
// Note that it is "section" as opposed to "sections" above
#pragma omp section
{
std::cout << "hello " << std::endl;
/** Do something **/
}
#pragma omp section
{
std::cout << "world " << std::endl;
/** Do something **/
}
}
// This line will not be executed until all the
// sections defined above terminates
std::cout << "end" << std::endl;
Outputs
This example produces 2 possible outputs and is dependent on the operating system and hardware. The output also illustrates a race condition problem that would occur from such an implementation.
| OUTPUT A | OUTPUT B |
|---|---|
| begin hello world end | begin world hello end |
