TRECV (3)
Receive with timeout.
SYNOPSIS
B
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
Integer to match task identifier of sending process.
Integer to match message tag;
should be >= 0.
(or sec and usec)
Time to wait before returning without a message.
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 following 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 msgtag 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 separate 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,
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_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
giving an invalid tid value, or msgtag < -1.
SEE ALSO
pvm_bufinfo(3PVM) pvm_getminfo(3PVM) pvm_nrecv(3PVM) pvm_recv(3PVM) pvm_unpack(3PVM) pvm_probe(3PVM) pvm_send(3PVM) pvm_mcast(3PVM)
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