Hi Matt, I am using PETSc-dev because only this version supports MatSetValuesBlockedStencil in Fortran. I tried many combinations of KSP and PC. None of them worked in my case. The same thing happened to PETSc-3.4.
Then I changed back to 3.3-P7 and 3.2-P7 without using MatSetValuesBlockedStencil. I tried KSPCR+PCBJACOBI and many others, they worked fine. I read the changes of each version, and still could not find the reason. Did I miss something? Thank you. ________________________________________ From: Matthew Knepley [[email protected]] Sent: Wednesday, December 04, 2013 4:19 PM To: Xiao, Jianjun (IKET) Cc: [email protected] Subject: Re: [petsc-users] Convergence problem in solving a symmetric positive definite matrix in a CFD code On Wed, Dec 4, 2013 at 8:59 AM, Xiao, Jianjun (IKET) <[email protected]<mailto:[email protected]>> wrote: Hello, I am using Petsc to solve the linear equation in a CFD code. The matrix is symmetric positive definite. Please find my input and output below. 1. When I used KSPCR solver, ||r(i)||/||b|| is inf. What is the reason? Does it mean ||b|| is zero? When I used the KSPLGMRES solver, it seems ||r(i)||/||b|| is OK. However, it seems the calculated results are not right. It looks that way. You can check it with VecNorm() before calling KSPSolve(). Matt 2. I am not sure if I set the solver and matrix properly. Did I miss something? Thank you. **************************************** INPUT: CALL KSPCreate(PETSC_COMM_WORLD,solver,ierr) CALL DMSetMatType(da_ksp,MATMPISBAIJ,ierr) CALL DMCreateMatrix(da_ksp,mat,ierr) CALL MatMPISBAIJSetPreallocation(mat,1,4,PETSC_NULL_INTEGER,1,PETSC_NULL_INTEGER,ierr) CALL MatZeroEntries(mat,ierr) CALL MatAssemblyBegin(mat,MAT_FINAL_ASSEMBLY,ierr) CALL MatAssemblyEnd(mat,MAT_FINAL_ASSEMBLY,ierr) CALL KSPSetOperators(solver,mat,mat,SAME_NONZERO_PATTERN,ierr) ! CALL KSPSetType(solver,KSPCR,ierr) CALL KSPSetType(solver,KSPLGMRES,ierr) epsi = 1.0-e5 CALL KSPSetTolerances(solver,epsi,PETSC_DEFAULT_DOUBLE_PRECISION,& & PETSC_DEFAULT_DOUBLE_PRECISION,itmax,ierr) CALL KSPGetPC(solver,gfprec,ierr) CALL PCSetType(prec,PCBJACOBI,ierr) CALL KSPMonitorSet(solver,KSPMonitorTrueResidualNorm,& PETSC_NULL_OBJECT,PETSC_NULL_FUNCTION,ierr ) CALL KSPSetInitialGuessNonzero(solver,PETSC_TRUE,ierr) CALL KSPSolve(solver,bvec,xsol,ierr) CALL KSPGetIterationNumber(solver,iter,ierr) CALL KSPGetResidualNorm(solver,dmax,ierr) CALL KSPView(solver,PETSC_VIEWER_STDOUT_WORLD,ierr) ************************************** OUTPUT CALL KSPSetType(solver,KSPCR,ierr): 0 KSP preconditioned resid norm 2.226482634319e+05 true resid norm 1.204978940624e+07 ||r(i)||/||b|| inf 1 KSP preconditioned resid norm 1.684243557244e+05 true resid norm 6.742321430949e+06 ||r(i)||/||b|| inf 2 KSP preconditioned resid norm 1.039386033131e+05 true resid norm 5.094347016880e+06 ||r(i)||/||b|| inf 3 KSP preconditioned resid norm 3.767761162917e+04 true resid norm 2.085014289432e+06 ||r(i)||/||b|| inf 4 KSP preconditioned resid norm 2.220316358489e+04 true resid norm 1.039841616110e+06 ||r(i)||/||b|| inf 5 KSP preconditioned resid norm 1.009108756815e+04 true resid norm 6.764592620620e+05 ||r(i)||/||b|| inf 6 KSP preconditioned resid norm 7.266143334386e+03 true resid norm 4.713756053613e+05 ||r(i)||/||b|| inf 7 KSP preconditioned resid norm 4.925270026573e+03 true resid norm 3.276759177651e+05 ||r(i)||/||b|| inf 8 KSP preconditioned resid norm 2.595039666791e+03 true resid norm 1.774916597474e+05 ||r(i)||/||b|| inf 9 KSP preconditioned resid norm 1.970388137453e+03 true resid norm 1.449811653036e+05 ||r(i)||/||b|| inf 10 KSP preconditioned resid norm 1.455914234388e+03 true resid norm 7.916294162841e+04 ||r(i)||/||b|| inf 11 KSP preconditioned resid norm 8.335194818556e+02 true resid norm 4.530953608250e+04 ||r(i)||/||b|| inf 12 KSP preconditioned resid norm 3.022320555777e+02 true resid norm 1.728551635678e+04 ||r(i)||/||b|| inf 13 KSP preconditioned resid norm 7.190336024797e+01 true resid norm 4.186842086105e+03 ||r(i)||/||b|| inf 14 KSP preconditioned resid norm 1.718291655675e+01 true resid norm 1.089751055004e+03 ||r(i)||/||b|| inf 15 KSP preconditioned resid norm 1.150683059424e+01 true resid norm 8.672405273471e+02 ||r(i)||/||b|| inf 16 KSP preconditioned resid norm 8.663479440949e+00 true resid norm 5.776737380768e+02 ||r(i)||/||b|| inf 17 KSP preconditioned resid norm 5.282161990683e+00 true resid norm 2.977735906695e+02 ||r(i)||/||b|| inf 18 KSP preconditioned resid norm 3.802629315725e+00 true resid norm 2.789114564993e+02 ||r(i)||/||b|| inf 19 KSP preconditioned resid norm 1.722575171383e+00 true resid norm 1.051323829526e+02 ||r(i)||/||b|| inf KSP Object: 1 MPI processes type: cr maximum iterations=1000 tolerances: relative=1e-05, absolute=1e-50, divergence=10000 left preconditioning using nonzero initial guess using PRECONDITIONED norm type for convergence test PC Object: 1 MPI processes type: bjacobi block Jacobi: number of blocks = 1 Local solve is same for all blocks, in the following KSP and PC objects: KSP Object: (sub_) 1 MPI processes type: preonly maximum iterations=10000, initial guess is zero tolerances: relative=1e-05, absolute=1e-50, divergence=10000 left preconditioning using NONE norm type for convergence test PC Object: (sub_) 1 MPI processes type: icc 0 levels of fill tolerance for zero pivot 2.22045e-14 using Manteuffel shift [POSITIVE_DEFINITE] matrix ordering: natural factor fill ratio given 1, needed 1 Factored matrix follows: Mat Object: 1 MPI processes type: seqsbaij rows=27, cols=27 package used to perform factorization: petsc total: nonzeros=81, allocated nonzeros=81 total number of mallocs used during MatSetValues calls =0 block size is 1 linear system matrix = precond matrix: Mat Object: 1 MPI processes type: seqsbaij rows=27, cols=27 total: nonzeros=81, allocated nonzeros=108 total number of mallocs used during MatSetValues calls =0 block size is 1 linear system matrix = precond matrix: Mat Object: 1 MPI processes type: mpisbaij rows=27, cols=27 total: nonzeros=81, allocated nonzeros=135 total number of mallocs used during MatSetValues calls =0 block size is 1 OUTPUT: CALL KSPSetType(solver,KSPLGMRES,ierr) 0 KSP preconditioned resid norm 2.362537325084e+04 true resid norm 1.138584383312e+06 ||r(i)||/||b|| 1.000000000000e+00 1 KSP preconditioned resid norm 8.501213683423e+03 true resid norm 3.655528853686e+05 ||r(i)||/||b|| 3.210591070162e-01 2 KSP preconditioned resid norm 5.487567253725e+03 true resid norm 3.005741194777e+05 ||r(i)||/||b|| 2.639893220769e-01 3 KSP preconditioned resid norm 2.470452880657e+03 true resid norm 1.545469272201e+05 ||r(i)||/||b|| 1.357360328187e-01 4 KSP preconditioned resid norm 1.750803325456e+03 true resid norm 1.182312309352e+05 ||r(i)||/||b|| 1.038405520646e-01 5 KSP preconditioned resid norm 1.123492053552e+03 true resid norm 6.754319630701e+04 ||r(i)||/||b|| 5.932208213726e-02 6 KSP preconditioned resid norm 5.150241959277e+02 true resid norm 3.689413898730e+04 ||r(i)||/||b|| 3.240351749775e-02 7 KSP preconditioned resid norm 4.182894544871e+02 true resid norm 3.052196222024e+04 ||r(i)||/||b|| 2.680693909701e-02 8 KSP preconditioned resid norm 2.520093155629e+02 true resid norm 1.880976788356e+04 ||r(i)||/||b|| 1.652031079932e-02 9 KSP preconditioned resid norm 1.186491314806e+02 true resid norm 6.797080217853e+03 ||r(i)||/||b|| 5.969764136483e-03 10 KSP preconditioned resid norm 5.851092821372e+01 true resid norm 2.973659280245e+03 ||r(i)||/||b|| 2.611716201127e-03 11 KSP preconditioned resid norm 1.669909189055e+01 true resid norm 5.658829814125e+02 ||r(i)||/||b|| 4.970057465277e-04 12 KSP preconditioned resid norm 3.090594692756e+00 true resid norm 2.161527454147e+02 ||r(i)||/||b|| 1.898434130864e-04 13 KSP preconditioned resid norm 2.164618839184e+00 true resid norm 1.620745991834e+02 ||r(i)||/||b|| 1.423474637093e-04 14 KSP preconditioned resid norm 1.291593952428e+00 true resid norm 9.095542547366e+01 ||r(i)||/||b|| 7.988465923722e-05 15 KSP preconditioned resid norm 6.100583411632e-01 true resid norm 4.021646656091e+01 ||r(i)||/||b|| 3.532146334551e-05 16 KSP preconditioned resid norm 2.723496807925e-01 true resid norm 1.676660466866e+01 ||r(i)||/||b|| 1.472583403954e-05 17 KSP preconditioned resid norm 1.377718471538e-01 true resid norm 8.551854245272e+00 ||r(i)||/||b|| 7.510953400221e-06 KSP Object: 1 MPI processes type: lgmres GMRES: restart=30, using Classical (unmodified) Gram-Schmidt Orthogonalization with no iterative refinement GMRES: happy breakdown tolerance 1e-30 LGMRES: aug. dimension=2 LGMRES: number of matvecs=170 maximum iterations=1000 tolerances: relative=1e-05, absolute=1e-50, divergence=10000 left preconditioning using nonzero initial guess using PRECONDITIONED norm type for convergence test PC Object: 1 MPI processes type: bjacobi block Jacobi: number of blocks = 1 Local solve is same for all blocks, in the following KSP and PC objects: KSP Object: (sub_) 1 MPI processes type: preonly maximum iterations=10000, initial guess is zero tolerances: relative=1e-05, absolute=1e-50, divergence=10000 left preconditioning using NONE norm type for convergence test PC Object: (sub_) 1 MPI processes type: icc 0 levels of fill tolerance for zero pivot 2.22045e-14 using Manteuffel shift [POSITIVE_DEFINITE] matrix ordering: natural factor fill ratio given 1, needed 1 Factored matrix follows: Mat Object: 1 MPI processes type: seqsbaij rows=27, cols=27 package used to perform factorization: petsc total: nonzeros=81, allocated nonzeros=81 total number of mallocs used during MatSetValues calls =0 block size is 1 linear system matrix = precond matrix: Mat Object: 1 MPI processes type: seqsbaij rows=27, cols=27 total: nonzeros=81, allocated nonzeros=108 total number of mallocs used during MatSetValues calls =0 block size is 1 linear system matrix = precond matrix: Mat Object: 1 MPI processes type: mpisbaij rows=27, cols=27 total: nonzeros=81, allocated nonzeros=135 total number of mallocs used during MatSetValues calls =0 -- 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
