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

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