TRECV(3PVM) PVM Version 3.4 TRECV(3PVM)NAME
pvm_trecv - Receive with timeout.
SYNOPSIS
C #include <sys/time.h>
int bufid = pvm_trecv( int tid, int msgtag, struct timeval *tmout )
Fortran call pvmftrecv( tid, msgtag, sec, usec, bufid )
PARAMETERS
tid Integer to match task identifier of sending process.
msgtag Integer to match message tag; should be >= 0.
tmout (or sec and usec) Time to wait before returning without a mes‐
sage.
bufid Integer returns the value of the new active receive buffer
identifier. Values less than zero indicate an error.
DESCRIPTION
The routine pvm_trecv blocks the process until a message with label
msgtag has arrived from tid. pvm_trecv then places the message in a
new active receive buffer, also clearing the current receive buffer.
If no matching message arrives within the specified waiting time,
pvm_trecv returns without a message.
A -1 in msgtag or tid matches anything. This allows the user the fol‐
lowing options. If tid = -1 then pvm_trecv will accept a message from
any process which has a matching msgtag. If msgtag = -1 then pvm_trecv
will accept any message that is sent from process tid. If tid and msg‐
tag are both -1, then pvm_trecv will accept any message from any
process.
In C, the tmout fields tv_sec and tv_usec specify how long pvm_trecv
will wait without returning a matching message. In Fortran, two sepa‐
rate parameters, sec and usec are passed. With both set to zero,
pvm_trecv behaves the same as pvm_nrecv, which is to probe for messages
and return immediately even if none are matched. In C, passing a null
pointer in tmout makes pvm_trecv act like pvm_recv, that is, it will
wait indefinitely. In Fortran, setting sec to -1 has the same effect.
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.
If pvm_trecv is successful, bufid will be the new active receive buffer
identifier. If no message is received, pvm_trecv returns 0. If some
error occurs then bufid will be < 0.
Once pvm_trecv returns, the data in the message can be unpacked into
the user's memory using the unpack routines.
EXAMPLES
C:
struct timeval tmout;
tid = pvm_parent();
msgtag = 4 ;
tmout.tv_sec = 60;
tmout.tv_usec = 0;
if ((bufid = pvm_trecv( tid, msgtag, &tmout )) > 0) {
pvm_upkint( tid_array, 10, 1 );
pvm_upkint( problem_size, 1, 1 );
pvm_upkfloat( input_array, 100, 1 );
}
Fortran:
CALL PVMFTRECV( -1, 4, 60, 0, BUFID )
IF (BUFID .EQ. 0) GO TO 666
CALL PVMFUNPACK( INTEGER4, TIDS, 25, 1, INFO )
CALL PVMFUNPACK( REAL8, MATRIX, 100, 100, INFO )
666 CONTINUE
ERRORS
These error conditions can be returned by pvm_trecv
PvmBadParam
giving an invalid tid value, or msgtag < -1.
PvmSysErr
pvmd not responding.
SEE ALSOpvm_bufinfo(3PVM), pvm_getminfo(3PVM), pvm_nrecv(3PVM), pvm_recv(3PVM),
pvm_unpack(3PVM), pvm_probe(3PVM), pvm_send(3PVM), pvm_mcast(3PVM)
8 February, 1994 TRECV(3PVM)
