3.2.2 PARALLEL REGION Directive

The PARALLEL REGION and END PARALLEL REGION directives delineate where parallelism exists in the program. The following example shows the PARALLEL REGION directive syntax:

C*KAP*          PARALLEL REGION
C*KAP*&          [ IF(logical expression) ]
C*KAP*&          [ SHARED(shared_name,...) ]
C*KAP*&          [ LOCAL(local_name,...) ]
C*KAP*          END PARALLEL REGION

In the syntax example, local_name and shared_ name are references to a variable or an array. If the IF clause logical expression evaluates to .FALSE., all of the code between PARALLEL REGION and END PARALLEL REGION executes on a single processor. If the logical expression evaluates to .TRUE., the code between the PARALLEL REGION and the corresponding END PARALLEL REGION may execute on multiple processors.

The SHARED and LOCAL lists on the PARALLEL REGION directive state the explicit forms of data sharing among the processors that execute the code inside the parallel region. When distinct processors reference the same variable or array from the SHARED list, the processors reference the same storage location. When distinct processors reference the same variable or array from the LOCAL list, the processors reference distinct storage locations.