Q. What do you mean by OpenMP?

OpenMP is a compiler directive based standard developed in late 1990s together by a group of main computer software and hardware vendors. It is portable across various popular platforms together with UNIX and Windows NT platforms. OpenMP FORTRAN API was released in 1997, October 28 and C/C++ API was released in late 1998. We will consider only C/C++ API.

The OpenMP API employs fork-join model of parallel execution. As soon as an OpenMP program begins executing it creates single thread of execution known as initial thread. The primary thread executes sequentially. The instant it gets a parallel construct the thread creates extra threads in addition works like master thread for all other threads. Every one of the new threads execute code inside parallel construct.  Only master thread continues execution of user code outside end of parallel construct. There is no limit on number of parallel constructs in a single program. When a thread with its child threads comes across a work sharing construct the work in construct is splitted among members of team and executed cooperatively in place of being executed by each thread. Execution of code by each thread in the team recommences after the end of work sharing construct. Synchronization constructs as well as library routines are accessible in OpenMP to coordinate threads and data in parallel and work-sharing constructs.