KSP/PC choice
Tim Kröger
tim at cevis.uni-bremen.de
Fri Jul 27 02:21:48 CDT 2007
Dear Matt
On Wed, 25 Jul 2007, Matthew Knepley wrote:
>> -ksp_type preonly
>> -pc_type lu
>> -mat_type aijmumps
>> -ksp_monitor
>>
> It appears that you never call MatSetFromOptions() on the matrix you
> create, which would prevent the option from changing the type.
Thank you very much for your help. Now, the MUMPS solver is working
for me, and it really seems to solve the problem that I was working on
for nearly a year now!
However, I have one more question: I usually call
KSPGetIterationNumber() after the solve, and if it tells me that 0 KSP
iterations have been used, I assume that the initial guess was already
accurate enough. In this case, I don't have to solve the system in
the next time steps anymore until some change of the setting takes
place (which happens from time to time in my application). This saves
a lot of computational time. However, with the MUMPS solver,
KSPGetIterationNumber() never supplies 0. Is there any possibility to
find out whether the initial guess was accurate enough?
(It might be noteworthy that I use "-ksptype richardson" instead of
"-ksptype preonly" since in the latter case I get an error message due
to my non-zero initial guess.)
Also, I would like to know whether there is any possibility to monitor
the convergence of the MUMPS solver (analogously to -kspmonitor).
Best Regards,
Tim
--
Dr. Tim Kroeger Phone +49-421-218-7710
tim at mevis.de, tim at cevis.uni-bremen.de Fax +49-421-218-4236
MeVis Research GmbH, Universitaetsallee 29, D-28359 Bremen, Germany
Amtsgericht Bremen HRB 16222
Geschaeftsfuehrer: Prof. Dr. H.-O. Peitgen
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