Synchronization#
Before the actual benchmark measurement is performed, several
consecutive barrier calls are made to ensure perfect processes
synchronization. The N_BARR constant defines the number of
consecutive calls. The constant is defined in IMB_settings.h and
IMB_settings_io.h, with the current value of 2.
The barrier calls are either ordinary MPI_Barrier(comm) calls, or
IMB_barrier(comm) calls (in case the –imb_barrier option is
specified).
See figure Control flow of IMB to understand the way all the processes are synchronized.