[petsc-users] How to set up -mat_mumps_icntl13 1 in the code?

[Barry Smith]

On May 16, 2012, at 5:51 AM, Giacomo Mulas wrote:

> On Tue, 15 May 2012, Barry Smith wrote:
> 
>>> So, if I understand correctly, I am supposed to call
>>> PetscOptionsInsertString() to add any options I want to have as defaults,
>>> then what is the call PetscOptionsInsert() for?
>> 
>>   It "resets" the options database with the command line options. If you
>> did not call this then the InsertString() options would not be overwritten
>> with the command line options.
> 
> Ah ok! It makes sense now that you explain. I could not quite understand
> this from the man pages :(
> 
>>  Ignore the PetscOptionsSetFromOptions() it has nothing to do with
>> anything there (it is just in that example to test it).  It does not
>> affect the options data base entries.
> 
> So I can omit that. Good. However, I suspect this is not the case for the
> similar slepc function EPSSetFromOptions(): I had to put that _after_ the
> PetscOptionsInsertString() call, or inserted options would be ignored by
> slepc. So I suppose the correct sequence should be:
> 
> PetscOptionsInsertString() # this adds my defaults
> PetscOptionsInsert()       # this has command line options replace defaults
> EPSSetFromOptions()        # this applies resulting options to my eps object
> 
> Is that right?

  Yes. Generally I would put the PetscOptionsInsertString() and PetscOptionsInsert() right at the beginning of the program after PetscInitialize() then you don't have to monkey with it later.  Meanwhile EPSSetFromOptions() comes later in the code whenever it comes.

   Barry

> 
> Thanks, bye
> Giacomo
> 
> -- 
> _________________________________________________________________
> 
> Giacomo Mulas <gmulas at oa-cagliari.inaf.it>
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