Note, as Barry said, GAMG works with native complex numbers. You can start with your original complex build and use '-pc_type gamg'. Mark
On Mon, Jul 23, 2018 at 6:52 AM Pierpaolo Minelli <pierpaolo.mine...@cnr.it> wrote: > > > > Il giorno 20 lug 2018, alle ore 19:58, Smith, Barry F. < > bsm...@mcs.anl.gov> ha scritto: > > > > > > > >> On Jul 20, 2018, at 7:01 AM, Pierpaolo Minelli < > pierpaolo.mine...@cnr.it> wrote: > >> > >> Hi, > >> > >> in my code I have to solve both a system in the field of real numbers > and in the field of complex numbers. > >> My approach has been as follows. > >> First I configured PETSc with the --with-scalar-type=complex option. > >> Using this option I have unfortunately lost the possibility to use the > two preconditioners ML and Hypre. > > > > You should still be able to use the PETSc PCGAMG algebraic multigrid > solver. Have you tried that? If there are issues let us know because we > would like to continue to improve the performance of PCGAMG to get it to be > closer to as good as ML and hypre. > > > > Barry > > > > I will try to convert, as suggested by Matthew, my complex system in a > system twice as large in real numbers. When i finish, i will try to use ML, > Hypre and GAMG and i let you know if there are any performance differences. > > Thanks > > Pierpaolo > > > >> I later created two subspaces of Krylov and tried to solve the two > systems as I used to when solving the only equation in the real numbers > field. > >> In order to correctly solve the system in the field of real numbers I > had to transform the coefficients from real to complex with an imaginary > part equal to zero. > >> > >> Is there a possibility to use a different and better approach to solve > my problem? > >> > >> Perhaps an approach where you can continue to use ML and Hypre for > system solving in the real numbers field or where you don't need to use > complex numbers when real numbers would actually suffice? > >> > >> Thanks in advance > >> > >> Pierpaolo > >> > > > >