[petsc-users] mat_view_info and the number of matrix objects

[Xiangdong Liang]

Hello everyone,

I am using mat_view_info to see the matrix information in ksp/ksp/ex2.c:
http://www.mcs.anl.gov/petsc/petsc-current/src/ksp/ksp/examples/tutorials/ex2.c.html

When I use single processor, I see two matrix-objects. One is the
operator A, but what's the other one? It seems that the other one
(always in seqaij or seqsbaij format) is from KSPSolve. What's the
purpose of that matrix object?

If I try two processors, I see five matrix-objects (more confused).
Can you help me understand where these "five" matrices come from?
Thanks.

Best,
Xiangdong




Here is the script:

-----------------------
 ./ex2 -mat_view_info

Matrix Object: 1 MPI processes
  type: seqaij
  rows=56, cols=56
  total: nonzeros=250, allocated nonzeros=280
  total number of mallocs used during MatSetValues calls =0
    not using I-node routines
Matrix Object: 1 MPI processes
  type: seqsbaij
  rows=56, cols=56
  package used to perform factorization: petsc
  total: nonzeros=153, allocated nonzeros=153
  total number of mallocs used during MatSetValues calls =0
      block size is 1
Norm of error 0.000156044 iterations 6

--------------------------------

mpirun -np 2 ./ex2 -mat_view_info

Matrix Object: 2 MPI processes
  type: mpiaij
  rows=56, cols=56
  total: nonzeros=250, allocated nonzeros=560
  total number of mallocs used during MatSetValues calls =0
    not using I-node (on process 0) routines
Matrix Object: 1 MPI processes
  type: seqaij
  rows=28, cols=28
  total: nonzeros=118, allocated nonzeros=118
  total number of mallocs used during MatSetValues calls =0
    not using I-node routines
Matrix Object: 1 MPI processes
  type: seqsbaij
  rows=28, cols=28
  package used to perform factorization: petsc
  total: nonzeros=73, allocated nonzeros=73
  total number of mallocs used during MatSetValues calls =0
      block size is 1
Matrix Object: 1 MPI processes
  type: seqaij
  rows=28, cols=28
  total: nonzeros=118, allocated nonzeros=118
  total number of mallocs used during MatSetValues calls =0
    not using I-node routines
Matrix Object: 1 MPI processes
  type: seqsbaij
  rows=28, cols=28
  package used to perform factorization: petsc
  total: nonzeros=73, allocated nonzeros=73
  total number of mallocs used during MatSetValues calls =0
      block size is 1
Norm of error 0.000411674 iterations 7