pvmfsiblings(3pvm) [debian man page]

SIBLINGS(3PVM)							  PVM Version 3.4						    SIBLINGS(3PVM)

NAME

       pvm_siblings -  return the number and associated task ids of processes that were started together in a single spawn call.

SYNOPSIS

       C    int ntids = pvm_siblings( int **tids )

       Fortran	 call pvmfsiblings( ntids, index, sibling )

PARAMETERS

       ntids   Returns the number of tids that were spawned together. Value less than 0 indicates an error.

       tids    Pointer to the array of tids that contains the siblings. Indexed from 0 to (ntids - 1)

       index   Integer	index  of tid to be returned in sibling. If index is set to -1, then sibling is unchanged. Otherwise, must be in the range
	       [0, ntids - 1]

       sibling When index is in the range [0, ntids -1], this contains the tid of the desired index.

DESCRIPTION

       The routine pvm_siblings returns the number of tasks and a list of task ids of processes that were spawned together in a single spawn call.
       The  spawning  task  multicasts	the  list  of successful to the spawned tasks so that each task has an identical copy of the sibling list.
       pvm_siblings uses local storage to keep the list of tids and does not update this list when sibling tasks exit the  virtual  machine.   The
       FORTRAN	version  allows calling programs read a particular index in the internal sibling array.  If pvm_siblings is successful, ntids will
       be  > 0. If some error occurs then ntids will be < 0.

       pvm_siblings is designed to simplify the logic in static spmd-style programs. By giving tasks an identical list of tids and its size,  pro-
       grams  may  self  size and treat the sibling as static map between instances and tasks. The internal list is not updated when sibling tasks
       exit the virtual machine and should be treated as a snapshot of the parallel program when it was first started.

       If a task was started by pvm_spawn, then pvm_siblings will return ntids = 1 and

       ntids = 1 and tids will contain a single entry identical to the task id returned by pvm_mytid()

EXAMPLES

       C:
	    int *tids;
	    ntids = pvm_siblings(&tids);

       Fortran:
	    INTEGER TIDS(0:MAXNPROC)
	    CALL PVMFSIBLINGS(NTIDS, -1, IDUM)
	    DO I = 0, NTIDS-1
	       CALL PVMFSIBLINGS(NTIDS, I, TIDS(I))

ERRORS

       pvm_siblings can return the following error codes

       PvmNoTask
	      No task at that index, or index is invalid.

SEE ALSO

       pvm_spawn(3PVM), pvm_mytid(3PVM), pvm_parent(3PVM)

								   26 June, 1997						    SIBLINGS(3PVM)

MCAST(3PVM)							  PVM Version 3.4						       MCAST(3PVM)

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 suc-
       cessful, 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)