NRECV(3PVM)							  PVM Version 3.4						       NRECV(3PVM)

NAME

       pvm_nrecv - Non-blocking receive.

SYNOPSIS

       C    int bufid = pvm_nrecv( int tid, int msgtag )

       Fortran	 call pvmfnrecv( 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.

DESCRIPTION

       The  routine  pvm_nrecv	checks	to see if a message with label msgtag has arrived from tid.  and also clears the current receive buffer if
       any, If a matching message has arrived pvm_nrecv immediately places the message in a new active receive	buffer,  and  returns  the  buffer
       identifier in bufid.

       If the requested message has not arrived, then pvm_nrecv immediately 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_nrecv will accept a message from any process which has a matching msgtag.  If msgtag =  -1  and  tid  is  defined  by  the  user,  then
       pvm_nrecv  will accept any message that is sent from process tid.  If tid = -1 and msgtag = -1, then pvm_nrecv will accept any message from
       any process.

       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.

       pvm_nrecv is non-blocking in the sense that the routine always returns immediately either with the message or with the information that the
       message	has  not  arrived  at the local pvmd yet.  pvm_nrecv can be called multiple times to check if a given message has arrived yet.	In
       addition the blocking receive pvm_recv can be called for the same message if the application runs out of work it could do before  the  data
       arrives.

       If pvm_nrecv returns with the message, then the data in the message can be unpacked into the user's memory using the unpack routines.

EXAMPLES

       C:
	    tid = pvm_parent();
	    msgtag = 4 ;
	    arrived = pvm_nrecv( tid, msgtag );
	    if ( arrived > 0)
		 info = pvm_upkint( tid_array, 10, 1 );
	    else
		 /* go do other computing */

       Fortran:
	    CALL PVMFNRECV( -1, 4, ARRIVED )
	    IF ( ARRIVED .gt. 0 ) THEN
	       CALL PVMFUNPACK( INTEGER4, TIDS, 25, 1, INFO )
	       CALL PVMFUNPACK( REAL8, MATRIX, 100, 100, INFO )
	    ELSE
       *       GO DO USEFUL WORK
	    ENDIF

ERRORS

       These error conditions can be returned by pvm_nrecv.

       PvmBadParam
	      giving an invalid tid value or msgtag.

       PvmSysErr
	      pvmd not responding.

SEE ALSO

       pvm_bufinfo(3PVM), pvm_getminfo(3PVM), pvm_recv(3PVM), pvm_unpack(3PVM), pvm_send(3PVM), pvm_mcast(3PVM)

								  30 August, 1993						       NRECV(3PVM)