The FLUSH directive identifies synchronization points at which the implementation must provide a consistent view of memory. It takes the following form:
Rules and Behavior
The FLUSH directive must appear at the precise point in the code at which the synchronization is required. To avoid flushing all variables, specify a list.
Thread-visible variables are written back to memory at the point at which this directive appears. Modifications to thread-visible variables are visible to all threads after this point. Subsequent reads of thread-visible variables fetch the latest copy of the data.
Thread-visible variables include the following data items:
The FLUSH directive is implied for the following directives (unless the NOWAIT keyword is used):
The following example uses the FLUSH directive for point-to-point synchronization between pairs of threads:
c$OMP PARALLEL DEFAULT(PRIVATE) SHARED(ISYNC) IAM = OMP_GET_THREAD_NUM() ISYNC(IAM) = 0 c$OMP BARRIER CALL WORK( ) C I AM DONE WITH MY WORK, SYNCHRONIZE WITH MY NEIGHBOR ISYNC(IAM) = 1 c$OMP FLUSH(ISYNC) C WAIT TILL NEIGHBOR IS DONE DO WHILE (ISYNC(NEIGH) .EQ. 0) c$OMP FLUSH(ISYNC) END DO c$OMP END PARALLEL