RECV (3)
Receive a message.
SYNOPSIS
B
C int bufid = pvm_recv( int tid, int msgtag )
Fortran call pvmfrecv( tid, msgtag, bufid )
PARAMETERS
Integer task identifier of sending process supplied by the user.
Integer message tag supplied by the user.
msgtag should be >= 0.
Integer returns the value of the new active receive buffer identifier.
Values less than zero indicate an error.
DESCRIPTION
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
giving an invalid tid value, or msgtag < -1.
SEE ALSO
pvm_bufinfo(3PVM) pvm_getminfo(3PVM) pvm_nrecv(3PVM) pvm_unpack(3PVM) pvm_probe(3PVM) pvm_send(3PVM) pvm_mcast(3PVM)
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