C int bufid = pvm_nrecv( int tid, int msgtag )
Fortran call pvmfnrecv( tid, msgtag, bufid )
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.
DESCRIPTIONThe 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.
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
ERRORSThese error conditions can be returned by pvm_nrecv.
- giving an invalid tid value or msgtag.
- pvmd not responding.