BARRIER(3PVM)

NAME
pvm_barrier - Blocks the calling process until all processes in a group have called it.

SYNOPSIS
C    int info = pvm_barrier( char *group, int count )
Fortran    call pvmfbarrier( group, count, info )

PARAMETERS

group
    Character string group name. The group must exist and the calling process must be a member of the group.

count
    Integer specifying the number of group members that must call pvm_barrier before they are all released. Though not required, count is expected to be the total number of members of the specified group.

info
    Integer status code returned by the routine. Values less than zero indicate an error.

DISCUSSION
The routine pvm_barrier blocks the calling process until count members of the group have called pvm_barrier. The count argument is required because processes could be joining the given group after other processes have called pvm_barrier. Thus PVM doesn't know how many group members to wait for at any given instant. Although count can be set less, it is typically the total number of members of the group. So the logical function of the pvm_barrier call is to provide a group synchronization. During any given barrier call all participating group members must call barrier with the same count value. Once a given barrier has been successfully passed, pvm_barrier can be called again by the same group using the same group name.

If pvm_barrier is successful, info will be 0. If some error occurs then info will be < 0.

EXAMPLES
C:
	inum = pvm_joingroup( "worker" );
	        .
	        .
	info = pvm_barrier( "worker", 5 );

Fortran:
	CALL PVMFJOINGROUP( "shakers", INUM )
	COUNT = 10
	CALL PVMFBARRIER( "shakers", COUNT, INFO )

ERRORS
These error conditions can be returned by pvm_barrier
	PvmSysErr	pvmd was not started or has crashed.
	PvmBadParam	giving a count < 1.
	PvmNoGroup	giving a non-existent group name.
	PvmNotInGroup	calling process is not in specified group.

SEE ALSO
joingroup(3PVM)