Two phase collective

Lewins, Lloyd J (llewins@msmail4.hac.com)
24 Jan 1997 08:28:39 -0800

The current proposal for two phase collective operations specifies that both
the "start" and "end" calls are collective. Since the existing rules (MPI-1)
specify that collective operations may be synchronizing, I would assert that
the operation can be performed by calling the "blocking" varient in either the
start or the end call (with the oposite call being a NO-OP).

If this is not the desired semantics, I would propose that the start
operations are not defined as collective. The end operations remain
collective. Two additional rules are required:

1) Start calls are local, their completion does not depend on the action of
any other process.

2) "End" calls match the preceding "start" call for the same collective
operation. When an "end" call is made, exactly one unmatched "start" call for
the same operation must preceed it.

Lloyd Lewins
Hughes Aircraft Co.,
llewins@msmail4.hac.com