[petsc-dev] IMP prototype

Jed Brown jedbrown at mcs.anl.gov
Thu Jan 2 10:03:20 CST 2014

Victor Eijkhout <eijkhout at tacc.utexas.edu> writes:

> On Dec 31, 2013, at 3:10 PM, Jed Brown <jedbrown at mcs.anl.gov> wrote:
>> Hmm, I don't really see the API for specifying the distributions.
>> rightshift->operate(">>1") is a pretty special-purpose interface.
>> Presumably this part is non-collective,
> No, it's collective. As I argue in section 1.1, I want sequential
> semantics.

Okay, but surely a more general interface for describing the
distribution must involve setting non-collectively (at least the data is
not collective, so you'll have to build the two-sided representation).

> It's actually not all that special purpose. The shift notation is
> enough if you have stencils with offsets that are constant during
> program execution.

Uh, only for structured grids, and for multiple dimensions, you either
need this communication abstraction to know about multi-dimensional
layout (essentially putting DMDA inside VecScatter) or you can't use the
shift notation.

> And you did read section 2.3, right?

Yeah, it's cute but limited and IMO, not very useful in practice.
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