I think I don't understand the meaning of -pc_type mpi -mpi_pc_type lu What's the exact meaning of -pc_type mpi and -mpi_pc_type lu?? Is this difference coming from 'mpi_linear_solver_server' option??
Thanks, Hyung Kim 2022년 12월 7일 (수) 오후 8:05, Matthew Knepley <[email protected]>님이 작성: > On Wed, Dec 7, 2022 at 5:13 AM 김성익 <[email protected]> wrote: > >> I want to use METIS for ordering. >> I heard the MUMPS has good performance with METIS ordering. >> >> However there are some wonder things. >> 1. With option "-mpi_linear_solver_server -ksp_type preonly -pc_type >> mpi -mpi_pc_type lu " the MUMPS solving is slower than with option >> "-mpi_linear_solver_server -pc_type mpi -ksp_type preonly". >> Why does this result happen? >> > > You are probably not using MUMPS. Always always always use -ksp_view to > see exactly what solver you are using. > > >> 2. (MPIRUN case (actually, mpi_linear_solver_server case))) In my code, >> there is already has "PetscCall(PCSetType(pc,PCLU))" . However, to use >> METIS by using "-mpi_mat_mumps_icntl_7 5" I must append this option >> "-mpi_pc_type pu". >> If I don't apply "-mpi_pc_type lu", the metis option >> ("-mpi_mat_mumps_icntl_7 5"). Can I get some information about this? >> > > Again, it seems like the solver configuration is not what you think it is. > > Thanks, > > Matt > > >> Thanks, >> Hyung Kim >> >> 2022년 12월 7일 (수) 오전 12:24, Barry Smith <[email protected]>님이 작성: >> >>> >>> >>> On Dec 6, 2022, at 5:15 AM, 김성익 <[email protected]> wrote: >>> >>> Hello, >>> >>> >>> I have some questions about pc and mumps_icntl. >>> >>> 1. What’s the difference between adopt preconditioner by code (for >>> example, PetscCall(PCSetType(pc,PCLU)) and option -pc_type lu?? >>> And also, What’s the priority between code pcsettype and option -pc_type >>> ?? >>> >>> 2. When I tried to use METIS in MUMPS, I adopted metis by option >>> (for example, -mat_mumps_icntl_7 5). In this situation, it is impossible to >>> use metis without pc_type lu. However, in my case pc type lu makes the >>> performance poor. So I don’t want to use lu preconditioner. How can I do >>> this? >>> >>> The package MUMPS has an option to use metis in its ordering process >>> which can be turned on as indicated while using MUMPS. Most >>> preconditioners that PETSc can use do not use metis for any purpose hence >>> there is no option to turn on its use. For what purpose do you wish to use >>> metis? Partitioning, ordering, ? >>> >>> >>> >>> >>> >>> >>> Thanks, >>> >>> Hyung Kim >>> >>> >>> > > -- > What most experimenters take for granted before they begin their > experiments is infinitely more interesting than any results to which their > experiments lead. > -- Norbert Wiener > > https://www.cse.buffalo.edu/~knepley/ > <http://www.cse.buffalo.edu/~knepley/> >
