[petsc-users] Set the options NOT from argc and argv

[Matthew Knepley]

On Mon, May 20, 2013 at 11:01 PM, Longxiang Chen <suifengls at gmail.com>wrote:

> The fortran program is too long (several files with more than 10,000
> lines).
> And I just want to insert the P_solve inside one of the subroutine to
> solve Ax=b.
> Or it can only use argc and argv?
>

Barry is correct that you can use PetscOptionsSetValue(), however I think
you are
still missing the point.

Command line options are processed in PetscInitialize(). You do not have to
do anything
else. You do not have to change your huge Fortran code. You just use the
command line.
It is much better than hard coding a solver type since you can use ALL
solver types. There
is no reason not to use it.

  Thanks,

     Matt


> Thanks.
> Longxiang
>
> Best regards,
> Longxiang Chen
>
> Do something every day that gets you closer to being done.
> --------------------------------------------------------------
> 465 Winston Chung Hall
> Computer Science Engineering
> University of California, Riverside
>
>
>
> On Mon, May 20, 2013 at 8:52 PM, Barry Smith <bsmith at mcs.anl.gov> wrote:
>
>>
>> On May 20, 2013, at 10:38 PM, Longxiang Chen <suifengls at gmail.com> wrote:
>>
>> > To whom it may concern,
>> >
>> > I am using KSP to solve Ax=b.
>> > The main() is in Fortran, and it calls a function I write in C.The
>> parameter is array A, x, b.
>> >
>> > void P_solve(double x[ ], double b[ ], double A[ ], int size);
>> >
>> > In the function, I should call PetscInitialize() before I create the
>> matrix and vectors for A, x, b, and also call MatSetFromOptions() and
>> VecSetFromOptions().
>> >
>> > But I don't have the argc and argv from main function.
>>
>>     If Fortran is the main program the options database still has access
>> to the command line arguments. You should still be able to use command line
>> arguments and not need to set them in the program.
>>
>>      Does this not work? Can you send a sample program where it does not
>> work?
>>
>>    Barry
>>
>> >
>> > I just want to fix the KSP type to bcgs and the PC type.
>> > Is there another way that I can set the options not through argc and
>> argv, just set them in the program.
>> >
>> > e.g. options[] = {"-ksp_type", "bcgs"}.
>> >
>> > Thanks,
>> > Longxiang
>>
>>
>


-- 
What most experimenters take for granted before they begin their
experiments is infinitely more interesting than any results to which their
experiments lead.
-- Norbert Wiener
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