NAME

pvm_trecv − Receive with timeout. 
 

SYNOPSIS

C#include <sys/time.h>
int bufid = pvm_trecv( int tid, int msgtag, struct timeval ∗tmout )
 Fortrancall pvmftrecv( tid, msgtag, sec, usec, bufid )

PARAMETERS

tidInteger to match task identifier of sending process. 

msgtagInteger to match message tag; should be >= 0. 

tmout(or sec and usec) Time to wait before returning without a message. 

bufidInteger 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 )
666CONTINUE

ERRORS

These error conditions can be returned by pvm_trecv

PvmBadParam
giving an invalid tid value, or msgtag < -1.

PvmSysErr
pvmd not responding.

SEE ALSO

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

  —  8 February, 1994