Gaetan Kenway <[email protected]> writes: > The untransposed system converges about 6 orders of magnitude with > GRMES(100), ASM (overlap 1) and ILU(1) with RCM reordering. The test is run > on 128 processors. There are no convergence difficulties. > > However, when I try to solve the transpose of the same system, by either > calling KSPSolveTranspose() or by assembling the transpose of the linear > system and its preconditioner and calling KSPSolve(), GMRES stagnates after > a negligible drop in the residual and no further progress is made.
Just a guess here, but the ASM default is "restricted ASM". Can you compare the nontransposed and transposed convergence with each of -pc_type <restrict,basic,interpolate> I.e., 6 runs in total; how does each converge or not?
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