[petsc-users] two-level Schwarz: PCMG or PCComposite

[Barry Smith]

   Yes,  src/ksp/pc/impls/composite/composite.c

On May 11, 2012, at 8:21 AM, Hui Zhang wrote:

> 
> On May 11, 2012, at 2:55 PM, Barry Smith wrote:
> 
>> 
>> If this is what you want to do then just use the PCCOMPOSITE. Use PC_COMPOSITE_SYMMETRIC_MULTIPLICATIVE
>> 
>>  Barry
> 
> Aha, I see.  Thank you, Barry!  
> Just one more question on PCCompositeAddPC:  is firstly added PC also firstly applied,
> i.e. the order of applying PC's is the same as the order of PCCompositeAddPC ?
> 
>> 
>> On May 11, 2012, at 6:26 AM, Hui Zhang wrote:
>> 
>>> I want to implement the two-level Schwarz method.  Let us denote P as the one-level
>>> Schwarz projection and P_0 as the coarse projection.  If I want the hybrid form of 
>>> preconditioned system as follows:
>>> 
>>>   (I-P_0) P (I-P_0) 
>>> 
>>> which is suitable:  PCMG or PCComposite?  It seems to me that PCComposite is good.
>>> But PCMG is not suitable because it can only implement the following form:
>>> 
>>>   (I-P) P_0 (I-P)
>>> 
>>> Any opinions?  Thanks!
>>> 
>>> 
>> 
>> 
>