[petsc-users] SetOptionsPrefix

[Barry Smith]

On Mar 30, 2013, at 7:53 PM, Jed Brown <jedbrown at mcs.anl.gov> wrote:

> Dharmendar Reddy <dharmareddy84 at gmail.com> writes:
>> Hello,
>>         I was wondering how the <SENS,KSP,PC>SetOptionsPrefix work ?. I
>> can figure out from the code that SNES set options prefix sets the options
>> prefix to the ksp and pc objects on snes. Does it also apply the prefix to
>> the Matrix and vectors passed to snes as jacobian, function and solution?
>> or, are they considered as a independent objects ? Do i need to set options
>> prefix to matrix and vector objects pased to snesset jacobian and snesset
>> function.
> 
> They are separate objects, but a prefix is automatically added to any
> (configurable) objects created internally by the solvers, including
> nested solvers.
> 
> If you want a unique prefix for the Jacobian, the preconditioning matrix
> (Pmat), or specific vectors, you should set it.

  But note that Vecs and Mats have essentially no runtime configurability related to the solvers being used, so usually there is no reason to provide prefixes to Mats and Vecs.

   Barry