SYNOPSIS

C int (*old)() = pvm_recvf( int (*new)( int bufid, int tid, int tag ))
Fortran NOT AVAILABLE

DESCRIPTION

The routine pvm_recvf defines the comparison function to be used by the pvm_recv, pvm_nrecv, and pvm_probe functions. It is available as a means to customize PVM message passing. pvm_recvf sets a user supplied comparison function to evaluate messages for receiving.

recvf returns the old value of the matching function, or 0 if the old function was the default matcher

pvm_recvf is intended for sophisticated C programmers who understand the function of such routines (like signal) and who require a receive routine that can match on more complex message contexts than the default provides.

MATCHING FUNCTION

The default comparison function evaluates the source and message tag associated with all incoming messages.

PARAMETERS

tid

Integer task identifier of sending process supplied by the user.

tag

Integer message tag supplied by the user.

bufid

Integer message buffer identifier.

The matching function should return:

     Value     Action taken
     < 0       Return immediately with this error code.
       0       Do not pick this message.
       1       Pick this message and do not scan the rest.
     > 1       Pick this highest ranked message after
               scanning them all.

EXAMPLES

Implementing message probe with recvf, using our matching function to return information in a global variable.

#include <pvm3.h>
static int foundit = 0;
static int
foo_match(mid, tid, tag)
     int mid;
     int tid;
     int tag;
{
     int t, c;
     struct pvmminfo header;
     pvm_getminfo(mid, &header);
     if ((tid == -1 || tid == header.src) && (tag == -1 || tag == header.tag))
          foundit = 1;
     return 0;
}
int
probe(src, tag)
{
     int (*omatch)();
     int cc;
     omatch = pvm_recvf(foo_match);
     foundit = 0;
     if ((cc = pvm_nrecv(src, tag)) < 0)
          return cc;
     pvm_recvf(omatch);
     return foundit;
}