On 04/04/2018 08:38 AM, Feimi Yu wrote:
I wish I can only deal with small problem, but that is only a test
problem and
I guess we need to use this code to compute much larger 3-D cases. Now it
is too slow so I cannot test any larger cases than 400k dofs. I tried
400k dofs,
still, 2 cores are slower than 1 core.
The weirdest thing is the iterations does not change much, when using block
jacobi this would change, but not significantly. Sometimes with Pilut
the number
of iterations even decreased, but with more time.
It's hard to tell what exactly is the problem without seeing the code
and/or more details. How many outer iterations do you need? How many
iterations do you need to solve for the Schur complement?
I would say that a good preconditioner for a problem with constant
coefficient should generally not require more than, say, 50-100 outer
iterations, and at most a similar number of inner iterations.
Maybe explain how your matrix block structure looks like, and how your
block solver/block preconditioner looks like?
Best
W.
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Wolfgang Bangerth email: [email protected]
www: http://www.math.colostate.edu/~bangerth/
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