> > 2) If you get "Indefinite PC" (I am guessing from using CG) it is because the > preconditioner > really is indefinite (or possible non-symmetric). We improved the > checking for this in one > of those releases. > > AMG does not guarantee an SPD preconditioner so why persist in trying to use > CG? >
AMG is positive if everything is working correctly. Are these problems only semidefinite? Singular systems can give erratic behavior.
