PROBE(3PVM)

NAME
pvm_probe - Check if message has arrived.

SYNOPSIS
C    int bufid = pvm_probe( int tid, int msgtag )
Fortran    call pvmfprobe( tid, msgtag, bufid )

PARAMETERS

tid Integer task identifier of sending process supplied by the user.

msgtag
    Integer message tag supplied by the user. msgtag should be >= 0.

bufid
    Integer returning the value of the new active receive buffer identifier. Values less than zero indicate an error.

DISCUSSION
The routine pvm_probe checks to see if a message with label msgtag has arrived from tid. If a matching message has arrived pvm_probe returns a buffer identifier in bufid. This bufid can be used in a pvm_bufinfo call to determine information about the message such as its source and length.

If the requested message has not arrived, then pvm_probe returns with a 0 in bufid. If some error occurs bufid will be < 0.

A -1 in msgtag or tid matches anything. This allows the user the following options. If tid = -1 and msgtag is defined by the user, then pvm_probe will accept a message from any process which has a matching msgtag. If msgtag = -1 and tid is defined by the user, then pvm_probe will accept any message that is sent from process tid. If tid = -1 and msgtag = -1, then pvm_probe will accept any message from any process.

pvm_probe can be called multiple times to check if a given message has arrived yet. After the message has arrived, pvm_recv must be called before the message can be unpacked into the user's memory using the unpack routines.

EXAMPLES
C:
	tid = pvm_parent();
	msgtag = 4 ;
	arrived = pvm_probe( tid, msgtag );
	if ( arrived )
		info = pvm_bufinfo( arrived, &len, &tag, &tid );
	else
		/* go do other computing */

Fortran:
	CALL PVMFPROBE( -1, 4, ARRIVED )
	IF ( ARRIVED .GT. 0 ) THEN
		CALL PVMFBUFINFO( ARRIVED, LEN, TAG, TID, INFO )
	ELSE
*		GO DO USEFUL WORK
	ENDIF

ERRORS
These error conditions can be returned by pvm_probe.
	PvmBadParam	giving an invalid tid value or msgtag.
	PvmSysErr	pvmd not responding.

SEE ALSO
nrecv(3PVM), recv(3PVM), unpack(3PVM)