ACENET Summer School - OpenMP: Glossary

OpenMP programs are limited to a single physical machine

You use OpenMP with C, C++, or Fortran

Pragmas are directives to the compiler to parallelize something

Thread number is typically controlled with an environment variable, OMP_NUM_THREADS

Order of execution of parallel elements is not guaranteed.

If the compiler doesn’t recognize OpenMP pragmas, it will compile a single-threaded program. But you may need to escape OpenMP function calls.

The PARALLEL FOR (or PARALLEL DO) pragma makes a loop execute in parallel

A single variable accessed by different threads can cause wrong results

The PRIVATE clause makes a copy of a variable for each thread

You can use a critical section to control access to a global variable

Reduction operators handle the common case of summation, and analogous operations

OpenMP can manage general parallel sections

You can use ‘pragma omp single’ to have a single thread execute something

OpenMP can manage general parallel tasks

Different loop scheduling may compensate for unbalanced loop iterations