SNESSetUp() and matrix-free options

Barry Smith bsmith at
Thu May 7 15:53:36 CDT 2009

   I don't have a problem with (somehow) merging the two options, but  
I don't see it
as a big improvement.

    -snes_mf -snes_mf_type both or operator

instead of -snes_mf or -snes_mf_operator

I don't see this as a big improvement.


On May 7, 2009, at 3:47 PM, Jed Brown wrote:

> Barry Smith wrote:
>> It is always possible someone has two options that conflict with each
>> other in the options database. This is suppose to generate an
>> error. and the only solution is for user to change one of them.
> My point is that -snes_mf and -snes_mf_operator are not really that
> different.  If there is only one option, then the options database  
> will
> only know about the last one and there is no conflict.  For example, I
> could put -pc_type lu in .petscrc, and then put -pc_type asm on the
> command line without conflicts.  I am suggesting making sure that  
> there
> is only one way to select the snes_mf variant on the command line in
> order to eliminate unnecessary possible conflicts.
> Jed

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