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NAME

pvm_recv - Receive a message.

SYNOPSIS

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

Fortran    call pvmfrecv( 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 returns the value of the new active receive buffer identifier. Values less than zero indicate an error.

DISCUSSION

The routine pvm_recv blocks the process until a message with label msgtag has arrived from tid. pvm_recv then places the message in a new active receive buffer, which also clears the current receive buffer.

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_recv will accept a message from any process which has a matching msgtag. If msgtag = -1 and tid is defined by the user, then pvm_recv will accept any message that is sent from process tid. If tid = -1 and msgtag = -1, then pvm_recv 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.

If pvm_recv is successful, bufid will be the value of the new active receive buffer identifier. If some error occurs then bufid will be < 0.

pvm_recv is blocking which means the routine waits until a message matching the user specified tid and msgtag values arrives at the local pvmd. If the message has already arrived then pvm_recv returns immediately with the message.

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

EXAMPLES

C:
   tid = pvm_parent();
   msgtag = 4 ;
   bufid = pvm_recv( tid, msgtag );
   info = pvm_upkint( tid_array, 10, 1 );
   info = pvm_upkint( problem_size, 1, 1 );
   info = pvm_upkfloat( input_array, 100, 1 );

Fortran:
   CALL PVMFRECV( -1, 4, BUFID )
   CALL PVMFUNPACK( INTEGER4, TIDS, 25, 1, INFO )
   CALL PVMFUNPACK( REAL8, MATRIX, 100, 100, INFO )

ERRORS

These error conditions can be returned by pvm_recv

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

SEE ALSO

pvm_nrecv(3PVM), pvm_unpack(3PVM), pvm_probe(3PVM), pvm_send(3PVM), pvm_mcast(3PVM)

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