[petsc-users] Implementation of Multilevel preconditioner

[Abdul Hanan Sheikh]

Hi users and developers, 
Summer greetings from Delft. 


For the system Au = f, I want to apply a multilevel preconditioner with a KSP (say FGMRES) . The preconditioner
reads as

Prec = C +  M^-1 (I - A*C) , where


	*  C reads coarse grid correction operator i.e. C =  P*A_2h\R  [ R  restriction, A_2h coarse operator, P interpolation] 
	* M is say some sparse matrix (resembling to A) 

What makes it multilevel is I have to approximate coarse operator "A_2h" with few KSP iterations preconditioned by the above defined
preconditioner "Prec" , but off course at the level 2h and hence at every coarse level until coarsest. 


I only know, it can be implemented with PCMG. I am little afraid of DMMG. 

Explanatory suggestions to customize PCMG for what is required are very appreciated. 


Thanks in advance. 


regards, Abdul 
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