Thanks for the notes. El mar, 4 mar 2025 a la(s) 2:22 p.m., Barry Smith (bsm...@petsc.dev) escribió:
> > > > On Mar 4, 2025, at 2:02 PM, Emmanuel Ayala <juan...@gmail.com> wrote: > > > > Hello everyone. > > > > I'm trying to solve a linear system (which comes from 3D FEM with > structured DM mesh) with a direct solver. I configured petsc installation > with mumps (–download-mumps –download-scalapack –download-parmetis > –download-metis, --download-hwloc, without ptscotch) and I have the > following functions: > > > > // K is the stiffness matrix, assembly correctly > > // U is the solution vector > > // RHS is the right hand side of the linear equation > > > > Mat Kfactor; > > > > ierr = MatGetFactor(K,MATSOLVERMUMPS, MAT_FACTOR_CHOLESKY, > &Kfactor); CHKERRQ(ierr); > > ierr = MatCholeskyFactorSymbolic(Kfactor,K,0,0); CHKERRQ(ierr); > > ierr = MatCholeskyFactorNumeric(Kfactor,K,0); CHKERRQ(ierr); > > ierr = MatSolve(Kfactor,RHS,U); > > > Note 1) these four lines of code above are not needed if you use are > using KSPSolve to solve the system. The options below will trigger this. > > > > and run with options: > > -pc_type cholesky -pc_factor_mat_solver_type mumps > -mat_mumps_icntl_1 1 -mat_mumps_icntl_13 0 -mat_mumps_icntl_28 2 > -mat_mumps_icntl_29 2 > OK. I'm solving sepparetelly the direct solver and the iterative one. > > Note 2) it is imperative you use a good BLAS library and optimization when > using mumps. Do not use --download-blaslapack (or friends) and use > --with-debugging=0 in the configure option). > Right. I configured it with --with-debugging=0 and --download-fblaslapack. *So, which is a good BLAS library?* from petsc: ...One can use --download-f2cblaslapack --download-blis... > > Note 3) If you are running sequentially (no MPI) then also ensure you have > --with-openmp in your configure options and set an appropriate value for > the number of OpenMP threads when you run your program. > I'm running with MPI . Regards. > > > > > > PROBLEM: > > I got the correct solution, but the function MatCholeskyFactorNumeric( ) > takes too much time to be completed. MatCholeskyFactorSymbolic() and > MatSolve() are very fast. The test uses a square K matrix of 700k dofs, and > the MatCholeskyFactorNumeric() takes around 14 minutes, while an iterative > solver (KSPCG/PCJACOBI) takes 5 seconds to get the solution. Any > suggestions? > > > > Thanks in advance. > >
