[MITgcm-support] Single reduction CG solver for pressure

Chris Hill cnh at mit.edu
Wed Jun 17 08:56:09 EDT 2009


 We did a version with two sums. I think it is ifdef'd in code. I
guess I had not realized you could get away with one some, although it
makes some sense since you only need one conjugate direction to
descend. I am doing some cg2d stuff this afternoon, so I'll take a
look at the D'Azevedo formulation.

On Tue, Jun 16, 2009 at 6:26 PM, Christopher L. Wolfe<clwolfe at ucsd.edu> wrote:
> Hi modelers,
> I was just wondering if anyone has tried to implement D'Azevedo et al.'s
> single reduction re-arrangement of the CG solver in cg2d. The GC solver
> currently does three reductions per step---one of which just checks the
> residual---and I find the model spends a lot of time waiting for the
> reductions to complete (especially on the Cray XTs). I think I may benefit
> from a rearrangement of the CG solver to reduce the number of global
> reductions, but I don't want to reinvent the wheel if someone else has
> already done it.
> Cheers,
> Christopher
> -----------------------------------------------------------
> Dr. Christopher L. Wolfe                   858-534-4560
> Physical Oceanography Research Division    OAR 357
> Scripps Institution of Oceanography, UCSD  clwolfe at ucsd.edu
> -----------------------------------------------------------
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