Dear all, I am trying get myself more acquainted with PETSc.
I am trying to solve a linear equation system which is conditioned badly. If I use the approach as given in ex1.c of the KSP section(by default, I read from the manual that it uses restarted GMRES , preconditioned with JACOBI in ex1.c which I am not very aware of these numerical procedures that in deep). I get some wrong results for the solution. I checked my results with Matlab, If I use the command line options as suggested on page 68 of the manual, to solve it directly, -ksp_type preonly -pc_type lu, I can both get the right solution and it is faster than the iterative solution which is used by default. So as far as I can follow from the mailing list, iterative methods and preconditioners are problem dependent, so my question would be, should I find the right approach/solver combination by some trial and error by using different combinations that are outlined in the manual?(This can also be dependent on the problem types that I would like to solve as well I suppose, for the moment, quite badly conditioned.) Any pointers are appreciated. Best regards, Umut
