KSP/PC choice

[Tim Kröger]

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

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