> Subject: Re: [petsc-users] questions about KSP with-pc_type hypre > From: [email protected] > Date: Mon, 7 Oct 2013 16:10:10 -0500 > CC: [email protected]; [email protected] > To: [email protected] > > > On Oct 7, 2013, at 3:28 PM, Roc Wang <[email protected]> wrote: > > > Sorry for the mis-info. > > > > Yes, I have Dirichlet BCs. The smaller round plate on the left side and the > > rectangular plane on the right size are the Dirichlet BCs. And the inside > > the hole of the rectangular plane is Neumann BCs. I am just wondering the > > Neumann BCs of the hole have some effect which lead to divergence. > > "Some" Neumann boundary conditions shouldn't have much effect. Are you > sure the Neumann BCs are applied correctly and that Neumann BCs are not being > applied everywhere? If Neumann BCs are applied almost everywhere on the > boundary that can affect convergence.
Yes, the Neumann BCs are applied correctly, since the solution is correct if the KSP solver runs without -pc_type hypre option. On the right side of the domain, the Neumann BCs are only within a hole in the center of the plane. > > What happens with -pc_type lu? Does it solve the linear system and give > back answers you expect? No, it doesn't work if I use -pc_type lu. The error information shows: [0]PETSC ERROR: --------------------- Error Message ------------------------------------ [0]PETSC ERROR: No support for this operation for this object type! [0]PETSC ERROR: Matrix format mpiaij does not have a built-in PETSc LU! [0]PETSC ERROR: ------------------------------------------------------------------------ [0]PETSC ERROR: Petsc Release Version 3.3.0, Patch 6, Mon Feb 11 12:26:34 CST 2013 [0]PETSC ERROR: See docs/changes/index.html for recent updates. [0]PETSC ERROR: See docs/faq.html for hints about trouble shooting. [0]PETSC ERROR: See docs/index.html for manual pages. [0]PETSC ERROR: ------------------------------------------------------------------------ [0]PETSC ERROR: ./x.r on a arch-linu named athena.coeaccess.psu.edu by pwang Tue Oct 8 10:23:50 2013 [0]PETSC ERROR: Libraries linked from /home/pwang/soft/petsc-3.3-p6/arch-linux2-c-debug/lib [0]PETSC ERROR: Configure run at Fri Oct 4 15:18:39 2013 [0]PETSC ERROR: Configure options --with-cc=gcc --with-fc=gfortran --download-f-blas-lapack --dtime elap.:0 0.0000 1000000 ownload-mpich --with-cxx=g++ --download-hypre=1 --download-ml=1 --download-hdf5=1 [0]PETSC ERROR: ------------------------------------------------------------------------ [0]PETSC ERROR: MatGetFactor() line 3876 in src/mat/interface/matrix.c [0]PETSC ERROR: PCSetUp_LU() line 133 in src/ksp/pc/impls/factor/lu/lu.c [0]PETSC ERROR: PCSetUp() line 832 in src/ksp/pc/interface/precon.c [0]PETSC ERROR: KSPSetUp() line 278 in src/ksp/ksp/interface/itfunc.c [0]PETSC ERROR: KSPSolve() line 402 in src/ksp/ksp/interface/itfunc.c [0]PETSC ERROR: LinearSolver() line 264 in "unknowndirectory/"src/solver.cpp rank 2 in job 959 athena.coeaccess.psu.edu_42121 caused collective abort of all ranks exit status of rank 2: killed by signal 6 rank 1 in job 959 athena.coeaccess.psu.edu_42121 caused collective abort of all ranks exit status of rank 1: killed by signal 6 How can I make -pc_type lu work? Thanks a lot > > > Barry > > > > > I will try gamg as your suggestion. Thanks. > > > > > > Subject: Re: [petsc-users] questions about KSP with-pc_type hypre > > From: [email protected] > > Date: Mon, 7 Oct 2013 16:16:30 -0400 > > CC: [email protected] > > To: [email protected] > > > > I assume this is a Lapacian and its not a pure Neumann problem. I did not > > quite follow you description. Do you have some Dirichlet BCs? > > > > Hypre is a very robust solver, for a scalable solver. ILU, the default PC, > > is very robust but slow (that's why its the default). You could try gamg, > > another AMG solver to get another data point. > > > > On Oct 7, 2013, at 3:08 PM, Roc Wang <[email protected]> wrote: > > > > Hello, > > > > I am trying to solve a linear system with KSP for a 3-D domain. The > > computational domain is a cubic space with Neumann condition on the lateral > > sides( y, and z directions). A smaller round plate is on the left side in > > x direction. The right side is a rectangular plane either with or without > > a hole. In testing studies, the KSP solver works fine both with and > > without -pc_type hypre runtime option for the domain with a whole > > plane(without a hole) on the right, but diverges for the case of a plane > > with a hole with -ps_type hypre option. > > > > My question is whether the hypre pre-conditioner is sensitive to the > > geometry boundary? If the answer is yes, is there any other > > pre-conditioner available for my particular case(the domain with a plane > > which with a hole on the right side) to reduce the number of iterations? > > Thanks in advance. > > > > >
