On Fri, 31 Jan 1997, Rolf Rabenseifner wrote:
> Date: Fri, 31 Jan 1997 16:27:43 +0100 (MEZ)
> From: Rolf Rabenseifner <Rabenseifner@RUS.Uni-Stuttgart.DE>
> To: mpi-external@mcs.anl.gov
> Cc: Thomas Boenisch <Thomas.Boenisch@RUS.Uni-Stuttgart.DE>
> Subject: two-face collective scenario
>
> An application scenario from real programmers life -- a background
> information for the two-faced collective proposal.
>
> Forwarded message:
> > From: Thomas Boenisch <Thomas.Boenisch@rus.uni-stuttgart.de>
> >
> > Hallo Rolf,
> >
> > I need a incomplite reduce and allreduce to hide communication time
> > and to avoid synchronisation in my application:
> >
> > One Iteration (programmed with your proposed two-faced...):
> >
> > call MPI_REDUCE_START(teilresl2, resl2, 1, REALx, MPI_SUM, 0,
> > . MPI_COMM_WORLD, info)
> > call MPI_ALLREDUCE_START(teilresl1, resl1, 1, REALx, MPI_SUM,
> > . mpi_comm_world_a, info)
> > call MPI_ALLREDUCE_START(teilresl0, resl0, 1, REALx, MPI_MAX,
> > . mpi_comm_world_b, info)
> >
> > c...solv the equationsystem
> > call parallelsolver( rm000, rmf00, rmb00, rm0f0, rm0b0, rm00f,
> > . rm00b, dq, rhs, nsubit, nhofhausit )
> >
> > c...computation of the CFL-Number with resl1
> > call MPI_ALLREDUCE_END(mpi_comm_world_a, resl1)
> > ...
> >
> > c...output of all residuals
> > call MPI_REDUCE_END(MPI_COMM_WORLD, resl2)
> > call MPI_ALLREDUCE_END(mpi_comm_world_b, resl0)
> > ...
> >
> > Ciao
> > Thomas
>
> This means that parts of the program (here the parallelsolver)
> can be overlayed with the effort for three reduce operations.
>
> Rolf
>
>
> Rolf Rabenseifner (Computer Center )
> Rechenzentrum Universitaet Stuttgart (University of Stuttgart)
> Allmandring 30 Phone: ++49 711 6855530
> D-70550 Stuttgart 80 FAX: ++49 711 6787626
> Germany rabenseifner@rus.uni-stuttgart.de
>
Anthony Skjellum, PhD, Associate Professor of Computer Science;
Mississippi State University, Department of Computer Science & NSF ERC
Butler, Rm 300, PO Box 9637, Corner of Perry&Barr, Mississippi State,MS 39762
(601)325-8435 FAX: (601)325-8997; http://www.erc.msstate.edu/~tony;
"Persistence is fertile." ; e-mail: tony@cs.msstate.edu; Try MPI!