On Wed, 2 May 2018 08:39:30 -0400
Charles Antonelli <c...@umich.edu> wrote:
> This seems to be crying out for MPI_Reduce.
No, the described reduction cannot be implemented with MPI_Reduce (note
the need for partial sums along the axis).
> Also in the previous solution given, I think you should do the
> MPI_Sends first. Doing the MPI_Receives first forces serialization.
It needs that. The first thing that happens is that the first rank
skips the recv and sends its SCAL to the 2nd process that just posted
recv.
Each process needs to complete the recv to know what to send (unless
you split it out into many more sends which is possible).
What's the best solution depends on if this part is performance
critical and how large K is.
/Peter K
> Regards,
> Charles
...
> > Something like (simplified psuedo code):
> >
> > if (not_first_along_K)
> > MPI_RECV(SCAL_tmp, previous)
> > SCAL += SCAL_tmp
> >
> > if (not_last_along_K)
> > MPI_SEND(SCAL, next)
> >
> > /Peter K
> > _______________________________________________
> > users mailing list
> > users@lists.open-mpi.org
> > https://lists.open-mpi.org/mailman/listinfo/users
> >
--
Sent from my Android device with K-9 Mail. Please excuse my brevity.
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