Parallelization of KSPSolve() in multidimensions
Rolf Kuiper
kuiper at mpia-hd.mpg.de
Wed May 20 10:28:27 CDT 2009
Hi PETSc-Users,
when solving an implicit equation with KSPSolve() in 3D (communication
with 7-point-stencil) I experienced the following:
Parallelization of the e.g. 64 x 64 x 64 domain on n cpus in the last
direction (every cpu has a 64 x 64 x 64/n subdomain) leads to a
parallel efficiency of approximately 90%, which is fine for us.
Parallelization of the e.g. 64 x 64 x 64 domain on n cpus in more than
one direction (every cpu has e.g. a 64 x 64/sqrt(n) x 64/sqrt(n)
subdomain) leads to a parallel efficiency of approximately 10%, which
is absolutely unusable.
Is this behavior generally true for this kind of solver? If so, why?
If not: What did I do wrong most presumably?
Has anybody made the same experience and/or could help me?
Thanks in advance,
Rolf
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