PROBE (3)

SYNOPSIS

B
C       int bufid = pvm_probe( int tid, int msgtag )
   

Fortran call pvmfprobe( tid, msgtag, bufid )

PARAMETERS

Integer task identifier of sending process supplied by the user.

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

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

DESCRIPTION

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 with pvm_bufinfo 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.
giving an invalid tid value or msgtag.

pvmd not responding.

SEE ALSO

pvm_bufinfo(3PVM) pvm_getminfo(3PVM) pvm_nrecv(3PVM) pvm_recv(3PVM) pvm_unpack(3PVM)