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

[Matthew Knepley]

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

     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
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