bionic (3) pvm_mcast.3PVM.gz

NAME

       pvm_mcast - Multicasts the data in the active message buffer to a set of tasks.

SYNOPSIS

       C    int info = pvm_mcast( int *tids, int ntask, int msgtag )

       Fortran   call pvmfmcast( ntask, tids, msgtag, info )

PARAMETERS

       ntask   Integer specifying the number of tasks to be sent to.

       tids    Integer array of length ntask containing the task IDs of the tasks to be sent to.

       msgtag  Integer  message  tag supplied by the user.  msgtag should be >= 0.  It allows the user's program
               to distinguish between different kinds of messages .

       info    Integer status code returned by the routine.  Values less than zero indicate an error.

DESCRIPTION

       The routine pvm_mcast multicasts a message stored in the active send buffer to ntask tasks  specified  in
       the  tids array.  The message is not sent to the caller even if listed in the array of tids.  The content
       of the message can be distinguished by msgtag.  If pvm_mcast is successful, info will be 0. If some error
       occurs then info will be < 0.

       The  receiving  processes  can  call either pvm_recv or pvm_nrecv to receive their copy of the multicast.
       pvm_mcast is asynchronous and based on a minimum spanning tree algorithm between the pvmds.   Computation
       on the sending processor resumes as soon as the message is safely on its way to the receiving processors.
       This is in contrast to synchronous communication, during which computation on the sending processor halts
       until the matching receive is executed by the receiving processor.

       pvm_mcast  first  determines  which  other pvmds contain the specified tasks.  Then passes the message to
       these pvmds which in turn distribute the message to their local tasks without further network traffic.

       Multicasting is not supported by most multiprocessor vendors.  Typically their native calls only  support
       broadcasting to {\m all the user's processes on a multiprocessor. Because of this omission, pvm_mcast may
       not be an efficient  communication  method  on  some  multiprocessors  except  in  the  special  case  of
       broadcasting to all PVM processes.

EXAMPLES

       C:
            info = pvm_initsend( PvmDataRaw );
            info = pvm_pkint( array, 10, 1 );
            msgtag = 5 ;
            info = pvm_mcast( tids, ntask, msgtag );

       Fortran:
            CALL PVMFINITSEND(PVMDEFAULT)
            CALL PVMFPACK( REAL4, DATA, 100, 1, INFO )
            CALL PVMFMCAST( NPROC, TIDS, 5, INFO )

ERRORS

       These error conditions can be returned by pvm_mcast

       PvmBadParam
              giving a msgtag < 0.

       PvmSysErr
              pvmd not responding.

       PvmNoBuf
              no send buffer.

SEE ALSO

       pvm_psend(3PVM), pvm_recv(3PVM), pvm_send(3PVM)

                                                 30 August, 1993                                     MCAST(3PVM)