I have a resistive mhd code that I have recently interfaced to petsc which has 7 linear solves that are all symmetric. I recently tried using -pc_type cholesky -ksp_type preonly for a run and found that it was taking about 6 times as long per linear solve as when I was using -pc_type lu -ksp_type preonly. I was wondering if that was reasonable behavior. I would not have thought that using a cholesky direct solve would take longer than an LU direct solve in petsc for the serial case and was hoping it would be faster. Does this behavior seem reasonable? Thanks, Dave -- Dave Nystrom phone: 505-661-9943 (home office) 505-662-6893 (home) skype: dave.nystrom76 email: [email protected] smail: 219 Loma del Escolar Los Alamos, NM 87544