[petsc-dev] composite vs. shell

[Jed Brown]

"Smith, Barry F." <bsmith at mcs.anl.gov> writes:

>> On Nov 9, 2017, at 11:13 PM, Jed Brown <jed at jedbrown.org> wrote:
>> 
>> "Smith, Barry F." <bsmith at mcs.anl.gov> writes:
>> 
>>>  Jed,
>>> 
>>>    Please articulate in a bit more detail. From what I can interpolate you are saying 
>>> 
>>> 1) that if we only propagate the outer matrices to inner matrices that the user has not set we will get a better more intuitive interface for users
>>> 
>>> but 
>>> 
>>> 2) the whole idea of propagating in is probably flawed.
>> 
>> The idea of having only two matrices, Amat and Pmat, is flawed.
>
>   Yes
>
>>  A
>> composite preconditioner, for example, may need more.  Having users
>> unwrap solvers to manually set matrices is ugly, but in lieu of a better
>> way (like named auxiliary matrices that can be requested by nested
>> preconditioners), we should honor the user's manual choices.
>
>    Yes. 
>
>     But you are not directly answering my question. Should we change
>     the code to not propagate if already set?

Yes, I think so.  That is what I meant by "we should honor the user's
manual choices" above.