[petsc-dev] MPIX_Iallreduce()

[Jed Brown]

On Sun, Mar 18, 2012 at 11:24, Matthew Knepley <knepley at gmail.com> wrote:

> This sounds fine to me. I think the acid test is to rewrite Bill's new CG
> in it.
>

Someone at ICERM knew the reference for that, right?


>
> I do not understand this. What call creates the PetscSplitReduction struct?


PetscSplitReductionGet(MPI_Comm) gets it out of the attribute cache on the
comm, creating it if it doesn't exist yet.


> Is it the Begins? So after Begin, it is present in
> the Vec and the Comm.
>

Currently only in the Comm, and it's always accessed the same way.


> Then when you call PetscCommSplitReductionBegin, it leaves the comm, and
> resides only in the
> Vec along with a Request. Then the End destroys it? So it lives in the
> Comm for aggregation purposes? That sounds fine to
> me.
>

Right, I want it to still live in the comm for aggregation purposes, but
have a reference count and have the link from the comm dropped when the
reduction starts.
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