MPI, short for Message Passing Interface, is a library that allows you to write parallel programs in Fortran77 or C. The library uses common operating system services to exchange information among the parallel processes it creates.
This method starts an RMA (Remote Memory Access) exposure epoch. To understand what an RMA exposure epoch is, we first need to understand active target communication.
Active target communication is when data is transferred from the memory of one process to the memory of another, and both processes are explicitly involved in the communication.
In active target communication, accessing a target window by RMA operations is restricted within an exposure epoch. This epoch is started and completed by RMA synchronization calls. MPI_Win_post is one such synchronization call.
int MPI_Win_post(MPI_Group group, int assert, MPI_Win win)
group is the set of origin processes for the epoch.
assert is used to optimize the function call; zero may be used as a default. Other assertion values include MPI_MODE_NOCHECK, MPI_MODE_NOSTORE, and MPI_MODE_NOPUT.
win is the window object. These objects are used to expose memory regions with which MPI processes can interact one-sidedly.
If unsuccessful, the function returns an error. The error, by default, aborts the MPI job.
In case of success, it returns MPI_SUCCESS, the value returned upon successful termination of any MPI routine.
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