[petsc-dev] Implementing longer pipelines with VecDotBegin and VecDotEnd

[Jed Brown]

Barry Smith <bsmith at mcs.anl.gov> writes:

>    Jed,
>
>       Ok I buy what you are saying as a possible solution but now I am
>       wondering why you need the request argument. Instead, as soon as
>       you hit the first End or PetscCommSplitReductionBegin why don't
>       you start a new batch (internally) that all new Begin() calls
>       feed into? Then each End call just checks through the previous
>       (still incompleted) batches to find its begin partner

How is the "begin partner" identified?

>       (or we can require always first in, first out). Thus your first
>       VecNormEnd(Y, would match the first begin with Y posted and your
>       second would match the second.

VecNormBegin(X,&norm);
function(X);
VecNormEnd(X,&norm);

would be broken if function() uses split reductions.
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