Dear All, I hope you're having a nice day. Compared the user manual of PETSc 3.1 and 3.4, I found that there are several 'new' KSP types are added. Then, I have some confusions on which KSP solver I need to pick. To my knowledge, if the matrix is symmetric, positive definite, the CG can be used. Otherwise, I have to use GMRES. My questions are: 1, What is the major difference among 'Conjugate Gradient', 'BiConjugate Gradient' and 'Conjugate Gradient Squared'? As I tested, the CGS is slightly (5%) faster than CG on solving a Poisson equation with uniform Cartesian grid with PC = GAMG. The BiCG is not tested because it seems not be compatible with PC = GAMG. 2, What is the major difference among GMRES, fGMRES and dGMRES. Specially, I want to solve a Poisson equation with non-uniform Cartesian grid. Theoretically, which 'GMRES' method would be the best for my case?
thanks, Alan
