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Message #09855
Re: [DOLFIN-DEV] Some Iterative Linear Solver Doubts.
On Thursday 25 September 2008, kent-and@xxxxxxxxx wrote:
> > On Thursday 25 September 2008, Matthew Knepley wrote:
> >> This is definitely wrong. Dave and I have been doing this all week here
> >> and those times are way way off.
> >
> > Sorry the time i show is the total time from the beggining of the
> > process. I get the following times:
> >
> > ----------------------------------------------------------------------
> > Solving linear system of size 566769 x 566769 (Krylov solver).
> > PETSc Krylov solver (gmres, sor) converged in 35 iterations.
> > Summary of timings | Average time Total time Reps
> > -----------------------------------------------------
> > ASSEMB_BC | 24.42 24.42 1
> > Assemble cells | 5.33 10.66 2
> > Build sparsity | 6.305 12.61 2
> > Delete sparsity | 0.125 0.25 2
> > GMRES_SOR | 35.86 35.86 1
> > Init dof map | 0.66 2.64 4
> > Init tensor | 0.16 0.32 2
> > End Process after 69.400000 seconds.
> > --------------------------------------------------------------------
>
> It seems a bit strange that only 35 iterations are required for such a
> fine mesh.
I'm testing with a large relative error 10^-5.
> Do you have a really good start vector?
That was my first doubt,
but for this simple case zero should be a good start vector, Ax=f
where f is nonzero only on the inflow boundary
> Or does the initial error only
> contain
> high frequency errors?
> Kent
>
--
Nuno David Lopes
e-mail:ndl@xxxxxxxxxxxxxx (FCUL/CMAF)
nlopes@xxxxxxxxxxxxxxx (ISEL)
http://ptmat.ptmat.fc.ul.pt/%7Endl/
Thu Sep 25 18:26:06 WEST 2008
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