NAME

pvm_trecv - Receive with timeout.

SYNOPSIS



C	#include <sys/time.h>


	int bufid = pvm_trecv( int tid, int msgtag, struct timeval *tmout )


Fortran	call pvmftrecv( tid, msgtag, sec, usec, bufid )

PARAMETERS

tid: Integer to match task identifier of sending process.
msgtag: Integer to match message tag; should be >= 0.
tmout: (or sec and usec) Time to wait before returning without a message.
bufid: Integer returns the value of the new active receive buffer identifier. Values less than zero indicate an error.

DESCRIPTION

The routine pvm_trecv blocks the process until a message with label msgtag has arrived from tid. pvm_trecv then places the message in a new active receive buffer, also clearing the current receive buffer. If no matching message arrives within the specified waiting time, pvm_trecv returns without a message.

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

In C, the tmout fields tv_sec and tv_usec specify how long pvm_trecv will wait without returning a matching message. In Fortran, two separate parameters, sec and usec are passed. With both set to zero, pvm_trecv behaves the same as pvm_nrecv, which is to probe for messages and return immediately even if none are matched. In C, passing a null pointer in tmout makes pvm_trecv act like pvm_recv, that is, it will wait indefinitely. In Fortran, setting sec to -1 has the same effect.

The PVM model guarantees the following about message order. If task 1 sends message A to task 2, then task 1 sends message B to task 2, message A will arrive at task 2 before message B. Moreover, if both messages arrive before task 2 does a receive, then a wildcard receive will always return message A.

If pvm_trecv is successful, bufid will be the new active receive buffer identifier. If no message is received, pvm_trecv returns 0. If some error occurs then bufid will be < 0.

Once pvm_trecv returns, the data in the message can be unpacked into the user's memory using the unpack routines.

EXAMPLES

C:
	struct timeval tmout;
	tid = pvm_parent();
	msgtag = 4 ;
	tmout.tv_sec = 60;
	tmout.tv_usec = 0;
	if ((bufid = pvm_trecv( tid, msgtag, &tmout )) > 0) {
		pvm_upkint( tid_array, 10, 1 );
		pvm_upkint( problem_size, 1, 1 );
		pvm_upkfloat( input_array, 100, 1 );
	}

Fortran:
	CALL PVMFTRECV( -1, 4, 60, 0, BUFID )
	IF (BUFID .EQ. 0) GO TO 666
	CALL PVMFUNPACK( INTEGER4, TIDS, 25, 1, INFO )
	CALL PVMFUNPACK( REAL8, MATRIX, 100, 100, INFO )
666	CONTINUE

ERRORS

These error conditions can be returned by pvm_trecv

PvmBadParam: giving an invalid tid value, or msgtag < -1.
PvmSysErr: pvmd not responding.