[petsc-users] ASM vs GASM

[Griffith, Boyce Eugene via petsc-users]

I am trying to setup a GASM preconditioner and am running into some difficulty 
getting convergence even with exact subdomain solvers. I am just doing things 
in serial now, and tried switching to ASM, and get convergence. I am wondering 
if I am misunderstanding the GASM interface. If inner_ises and outer_ises 
define the “inner” and “outer” subdomains for GASM, should GASM and ASM do the 
same things when configured via:

        PCGASMSetSubdomains(pc, n_subdomains, inner_ises, outer_ises);

and

        PCASMSetLocalSubdomains(pc, n_subdomains, outer_ises, inner_ises);

Thanks!

— Boyce