PETSc is slowing down in C++? continued

[xiaoyin ji]

Hi,

Here are the print outs

for the very beginning, average time is about 0.8sec for the ksp solver
KSP Object:
  type: bicg
  maximum iterations=10000, initial guess is zero
  tolerances:  relative=1e-07, absolute=1e-50, divergence=10000
  left preconditioning
PC Object:
  type: bjacobi
    block Jacobi: number of blocks = 16
    Local solve is same for all blocks, in the following KSP and PC objects:
  KSP Object:(sub_)
    type: preonly
    maximum iterations=10000, initial guess is zero
    tolerances:  relative=1e-05, absolute=1e-50, divergence=10000
    left preconditioning
  PC Object:(sub_)
    type: ilu
      ILU: 0 levels of fill
      ILU: factor fill ratio allocated 1
      ILU: tolerance for zero pivot 1e-12
      ILU: using diagonal shift to prevent zero pivot
      ILU: using diagonal shift on blocks to prevent zero pivot
           out-of-place factorization
           matrix ordering: natural
      ILU: factor fill ratio needed 1
           Factored matrix follows
          Matrix Object:
            type=seqaij, rows=5672, cols=5672
            package used to perform factorization: petsc
            total: nonzeros=39090, allocated nonzeros=39704
              not using I-node routines
    linear system matrix = precond matrix:
    Matrix Object:
      type=seqaij, rows=5672, cols=5672
      total: nonzeros=39090, allocated nonzeros=39704
        not using I-node routines
  linear system matrix = precond matrix:
  Matrix Object:
    type=mpiaij, rows=90746, cols=90746
    total: nonzeros=636378, allocated nonzeros=1279114
      not using I-node (on process 0) routines
Norm of error 48.144, Iterations 137

After 4000 steps, solver takes 7.5sec

KSP Object:
  type: bicg
  maximum iterations=10000, initial guess is zero
  tolerances:  relative=1e-07, absolute=1e-50, divergence=10000
  left preconditioning
PC Object:
  type: bjacobi
    block Jacobi: number of blocks = 16
    Local solve is same for all blocks, in the following KSP and PC objects:
  KSP Object:(sub_)
    type: preonly
    maximum iterations=10000, initial guess is zero
    tolerances:  relative=1e-05, absolute=1e-50, divergence=10000
    left preconditioning
  PC Object:(sub_)
    type: ilu
      ILU: 0 levels of fill
      ILU: factor fill ratio allocated 1
      ILU: tolerance for zero pivot 1e-12
      ILU: using diagonal shift to prevent zero pivot
      ILU: using diagonal shift on blocks to prevent zero pivot
           out-of-place factorization
           matrix ordering: natural
      ILU: factor fill ratio needed 1
           Factored matrix follows
          Matrix Object:
            type=seqaij, rows=5672, cols=5672
            package used to perform factorization: petsc
            total: nonzeros=39090, allocated nonzeros=39704
              not using I-node routines
    linear system matrix = precond matrix:
    Matrix Object:
      type=seqaij, rows=5672, cols=5672
      total: nonzeros=39090, allocated nonzeros=39704
        not using I-node routines
  linear system matrix = precond matrix:
  Matrix Object:
    type=mpiaij, rows=90746, cols=90746
    total: nonzeros=636378, allocated nonzeros=1279114
      not using I-node (on process 0) routines
Norm of error 48.7467, Iterations 132


The iterations are similar, solving time is actually increasing
exponentially, and the matrix should not be too complicated here as
the PETSc in Fortran solved this in 1sec.

By the way, will there be a way to set a PETSc vector directly into a
preconditioner for the ksp solver?

Thanks!

Best,
Xiaoyin Ji

Department of Materials Science and Engineering
North Carolina State University