[petsc-users] default orthogonalization in gmres

Jed Brown jedbrown at mcs.anl.gov
Mon Jul 15 18:05:17 CDT 2013

Karl Rupp <rupp at mcs.anl.gov> writes:

> well, you see the factor of k only if the communication for the 
> reduction is the bottleneck. The factor of almost 2 is what you get if 
> memory bandwidth is the bottleneck.

Sure, but reductions are the bottleneck if you try to strong scale,
especially if you don't have a Blue Gene.
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