changing default values in options database

Boyce Griffith griffith at
Fri Nov 7 12:06:21 CST 2008

Hi, Folks --

I'm using some KSP solvers in a preconditioner (using FGMRES as the 
"outer" Krylov solver).  For these preconditioner KSPs, I generally want 
to use relatively loose relative convergence tolerances.

Presently, I check to see if, e.g., -solver1_ksp_rtol, 
-solver2_ksp_atol, -solver3_max_it, etc., are set in the options 
database.  If a particular value is not set in the options database, I 
manually set that value to some value which is different from the 
default PETSc value.  Of course, when I use the `-help' flag, the help 
for each of the solvers indicates the default values for rtol, atol, 
max_it, etc. are the standard PETSc defaults.

Is there a simple way to change these default values for individual 
solvers?  In particular, I would like to be able to ensure that the 
default values listed by `-help' correspond to the values that I'm 
specifying in the code.


-- Boyce

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