[petsc-users] Solving block systems with some null diagonal blocks

[Manuel Colera Rico]

Hello,

I would like to solve a N*N block system (with N>2) in which some of the 
diagonal blocks are null. My system matrix is defined as a MatNest. As 
N>2, I can't use "pc_fieldsplit_type schur" nor 
"pc_fieldsplit_detect_saddle_point". The other algorithms ("additive", 
"multiplicative" and "symmetric_multiplicative") don't work either as 
they need each A_ii to be non-zero.

Is there any built-in function in PETSc for this? If not, could you 
please suggest a workaround?

Thanks and kind regards,

Manuel

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