I think one main goal of 1-sided is to allow extremly fast
point-to-point data exchange without blocking the application
by collective synchronization or barriers.
Barriers are easy to program but efficient only in well balanced
applications. In the big area of FE applications,
MPI_PUT and MPI_CONSUME_COUNTER can be more efficient.
And I want to remember, that describing WINDOW_IN and WINDOW_OUT
with the model of a public and a private copy is only a
trick to educate the user in a easy manner, it is not the
way MPI_PUT and MPI_GET should be implemented.
(The only known case, were efficiency is wished but not guaranted
is the case of 32 bit writes over HIPPI -- here the window must be
locked, but only for these writes, not for 64 bit writes)
Therefore I think the current modell is better than the
"proposal to change the direction of 1-sided comm".
Rolf Rabenseifner (Computer Center )
Rechenzentrum Universitaet Stuttgart (University of Stuttgart)
Allmandring 30 Phone: ++49 711 6855530
D-70550 Stuttgart 80 FAX: ++49 711 6787626