NOTIFY(3PVM)

NAME
pvm_notify - Request notification of PVM event such as host failure.

SYNOPSIS
C	int info = pvm_notify( int what, int msgtag, int cnt, int *tids )
Fortran	call pvmfnotify( what, msgtag, cnt, tids, info )

PARAMETERS

what
    Type of event to trigger the notification. Presently one of:
    	Value	Meaning
    	PvmTaskExit	Task exits or is killed
    	PvmHostDelete	Host is deleted or crashes
    	PvmHostAdd	New host is added

msgtag
    Message tag to be used in notification.

cnt For PvmTaskExit and PvmHostDelete, specifies the length of the tids array. For PvmHostAdd, specifies the number of times to notify.

tids
    For PvmTaskExit and PvmHostDelete, an array of length cnt of task or pvmd TIDs to be notified about. The array is not used with the PvmHostAdd option.

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

DESCRIPTION
The routine pvm_notify requests PVM to notify the caller on detecting certain events. One or more notify messages (see below) are sent by PVM back to the calling task. The messages have tag msgtag supplied to notify. The notification messages have the following format:

PvmTaskExit
    One notify message for each TID requested. The message body contains a single TID of exited task.

PvmHostDelete
    One notify message for each TID requested. The message body contains a single pvmd-TID of exited pvmd.

PvmHostAdd
    cnt notify messages are sent, one each time the local pvmd's host table is updated. The message body contains an integer length followed by a list of pvmd-TIDs of new pvmds. The counter of PvmHostAdd messages yet to be sent is replaced by successive calls to pvm_notify. Specifying a cnt of -1 turns on PvmHostAdd messages until a future notify; a count of zero disables them.

TIDs in the notify messages are packed as integers.

The calling task is responsible for receiving messages with the specified tag and taking appropriate action.

Future versions of PVM may expand the list of available notification events.

EXAMPLES
C:
	info = pvm_notify( PvmTaskExit, 9999, ntask, tids );

Fortran:
	CALL PVMFNOTIFY( PVMHOSTDELETE, 1111, NUMHOSTS, DTIDS, INFO )

To "cancel" a notify request in PVM, the pvm_notify routine can be re-invoked with an additional PvmNotifyCancel flag in the what argument. The remaining arguments to this cancelling invocation must match the original invocation exactly, aside from the additional PvmNotifyCancel which can be added(+) or OR-ed(|) to the what argument:
	pvm_notify( PvmTaskExit, 9999, ntask, tids );
	. . .
	pvm_notify( PvmTaskExit | PvmNotifyCancel, 9999, ntask, tids );
Note that when a notify is cancelled, the notify message is delivered, as if the given event (i.e. task exit, host add or delete) had occurred.

ERRORS

PvmSysErr
    pvmd not responding.

PvmBadParam
    giving an invalid argument value.

SEE ALSO
pvm_tasks(3PVM), pvm_config(3PVM)