[petsc-users] why a certain option cannot be used

[Matthew Knepley]

On Wed, Jul 16, 2014 at 4:25 PM, Matthew Knepley <knepley at gmail.com> wrote:

> On Wed, Jul 16, 2014 at 4:22 PM, Sun, Hui <hus003 at ucsd.edu> wrote:
>
>>  Thank you Matt for answering, however even with that I don't think it
>> works. For example, the command
>>
>>   ./ex70 -nx 32 -ny 48 -fieldsplit_1_type jacobi
>>
>
> You have mistyped. Look carefully at my last message:
>
>   -fieldsplit_1_pc_type jacobi
>

I also want to note that you can see all the available options with -help.
It does produce
a lot of output, but you can segregate it by prefix ("fieldsplit_1_"). You
can also see the
prefix of each solver component using -ksp_view.

  Matt


>      Matt
>
>
>>  gives me the following output
>>
>>
>>  residual u = 2.6315e-05
>>
>>  residual p = 0.000229872
>>
>>  residual [u,p] = 0.000231373
>>
>>  discretization error u = 0.00633503
>>
>>  discretization error p = 0.121534
>>
>>  discretization error [u,p] = 0.121699
>>
>> WARNING! There are options you set that were not used!
>>
>> WARNING! could be spelling mistake, etc!
>>
>>  Option left: name:-fieldsplit_1_type value: jacobi
>>
>>
>>  Furthermore, if I look into the possible options with keyword
>> fieldsplit involved by the command:
>>
>>
>>  ./ex70 -help | grep -A5 fieldsplit
>>
>>
>>  I get this output:
>>
>>
>>  eisenstat ilu icc cholesky asm gasm ksp composite redundant nn mat
>> fieldsplit galerkin exotic hmpi asa cp lsc redistribute svd gamg tfs
>> (PCSetType)
>>
>>   -pc_use_amat: <FALSE> use Amat (instead of Pmat) to define
>> preconditioner in nested inner solves (PCSetUseAmat)
>>
>> Krylov Method (KSP) options
>> -------------------------------------------------
>>
>>   -ksp_type <gmres>: Krylov method (one of) cg groppcg pipecg cgne nash
>> stcg gltr richardson
>>
>>       chebyshev gmres tcqmr bcgs ibcgs fbcgs fbcgsr bcgsl cgs tfqmr cr
>> pipecr lsqr preonly qcg bicg fgmres minres symmlq lgmres lcd gcr pgmres
>> specest dgmres (KSPSetType)
>>
>>    -ksp_max_it <10000>: Maximum number of iterations (KSPSetTolerances)
>>
>>
>>  So I don't see any option that's similar to -fieldsplit_1_type.
>>
>>
>>  Hui
>>
>>
>>
>>  ------------------------------
>> *From:* Matthew Knepley [knepley at gmail.com]
>> *Sent:* Wednesday, July 16, 2014 2:16 PM
>> *To:* Sun, Hui
>> *Cc:* petsc-users at mcs.anl.gov
>> *Subject:* Re: [petsc-users] why a certain option cannot be used
>>
>>    On Wed, Jul 16, 2014 at 4:09 PM, Sun, Hui <hus003 at ucsd.edu> wrote:
>>
>>>  I want to solve Stokes equation using user defined schur complement
>>> preconditioner. So I'm reading and testing snes/examples/tutorial/ex55.c,
>>> and ex70.c. In these examples, there are comments about the usage, for
>>> example:
>>>
>>>  mpiexec -n 2 ./stokes -nx 32 -ny 48 -fieldsplit_1_user_pc.
>>>
>>>  However the option -fieldsplit_1_user_pc is not recognized by the
>>> executable. The output of the above command is:
>>>
>>
>>  This ("user_pc") is just a mnemonic. What it means is that you can use
>> any PC in this slot. What he should have written is
>>
>>    -fieldsplit_1_pc_type <user pc>
>>
>>    Thanks,
>>
>>       Matt
>>
>>
>>>    residual u = 2.6315e-05
>>>
>>>  residual p = 0.000229872
>>>
>>>  residual [u,p] = 0.000231373
>>>
>>>  discretization error u = 0.00633503
>>>
>>>  discretization error p = 0.121534
>>>
>>>  discretization error [u,p] = 0.121699
>>>
>>> WARNING! There are options you set that were not used!
>>>
>>> WARNING! could be spelling mistake, etc!
>>>
>>> Option left: name:-fieldsplit_1_user_pc (no value)
>>>
>>>
>>>  I'm wondering what's going on. Is that because I need some specific
>>> options during my configuring of the package? By the way, the version of
>>> PETSc I'm using is 3.4.4.
>>>
>>>
>>>  Best,
>>>
>>> Hui
>>>
>>
>>
>>
>>  --
>> 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
>>
>
>
>
> --
> 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
>



-- 
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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