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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 mes-
       sage  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 fol-
       lowing 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, mes-
       sage A will arrive at task 2 before message B.  Moreover, if both  mes-
       sages 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 addi-
       tion 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 ar-
       rives.

       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_un-
       pack(3PVM), pvm_send(3PVM), pvm_mcast(3PVM)

				30 August, 1993			   NRECV(3PVM)

NAME | SYNOPSIS | PARAMETERS | DESCRIPTION | EXAMPLES | ERRORS | SEE ALSO

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