PROBE(3PVM) — Subroutines

NAME

pvm_probe − Check if message has arrived.

SYNOPSIS

Cint bufid = pvm_probe( int tid, int msgtag )

Fortrancall pvmfprobe( tid, msgtag, bufid )

PARAMETERS

tidInteger task identifier of sending process supplied by the user.

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

bufidInteger 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 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.

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