Image control statements

Standard: F77 F90 F95 F2003 F2008 F2018

＜Semantics＞

Execution on each image is divided into segments, by “image control statements”. The segments on a single image are ordered: each segment follows the preceding segment. Segments on diffrrent images may be ordered (one following the other) by synchronisation, otherwise they are unordered. If a coarray is defined (assigned a value) in a segment on image I, another image J is only allowed to reference or define it in a segment that either follows or precedes the segment on I. That is, reference or a conflicting definition in an unordered segment is not permitted.

Note that image control statements all have side-effects, and therefore are not allowed in PURE subprograms or DO CONCURRENT constructs.

＜List of image control statements＞

ALLOCATE if an object being allocated is a coarray;
CALL MOVE_ALLOC, if the FROM and TO arguments are coarrays;
CHANGE TEAM;
CRITICAL;
DEALLOCATE if an object being deallocated is a coarray;
END BLOCK, END FUNCTION, or END SUBROUTINE if that causes automatic deallocation of an allocatable coarray;
END CRITICAL;
END TEAM;
EVENT POST;
EVENT WAIT;
FORM TEAM;
LOCK;
STOP;
SYNC ALL;
SYNC IMAGES;
SYNC MEMORY;
UNLOCK.