MCAST(3PVM) PVM Version 3.4 MCAST(3PVM)NAMEpvm_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 differ‐
ent 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 success‐
ful, 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. Computa‐
tion on the sending processor resumes as soon as the message is safely
on its way to the receiving processors. This is in contrast to syn‐
chronous communication, during which computation on the sending proces‐
sor halts until the matching receive is executed by the receiving pro‐
cessor.
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. Typi‐
cally 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 multi‐
processors except in the special case of broadcasting to all PVM pro‐
cesses.
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 ALSOpvm_psend(3PVM), pvm_recv(3PVM), pvm_send(3PVM)
30 August, 1993 MCAST(3PVM)
