[petsc-users] subprocess (block) tolerance.

[HeeHo Park]

Hi, I'm running PFLOTRAN and in PFLOTRAN, we have flow_ and flow_sub_
processes. I was wondering what the red underlined values meant (each block
tolerance?) and how to change them (would it affect convergence?). Blue
marked bold values are changed from the default values for linear solvers.

FLOW Linear Solver
                       solver: bcgs
               preconditioner: asm
                         *atol: 1.000000E-10*
*                         rtol: 1.000000E-10*
                         dtol: 1.000000E+04
            maximum iteration: 10000
KSP Object: (flow_) 8 MPI processes
  type: bcgs
  maximum iterations=10000, initial guess is zero
  tolerances: * relative=1e-10, absolute=1e-10*, divergence=10000.
  left preconditioning
  using PRECONDITIONED norm type for convergence test
PC Object: (flow_) 8 MPI processes
  type: asm
    Additive Schwarz: total subdomain blocks = 8, amount of overlap = 1
    Additive Schwarz: restriction/interpolation type - RESTRICT
    [0] number of local blocks = 1
    [1] number of local blocks = 1
    [2] number of local blocks = 1
    [3] number of local blocks = 1
    [4] number of local blocks = 1
    [5] number of local blocks = 1
    [6] number of local blocks = 1
    [7] number of local blocks = 1
    Local solve info for each block is in the following KSP and PC objects:
    - - - - - - - - - - - - - - - - - -
    [0] local block number 0, size = 1389
    KSP Object: (flow_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 DEFAULT norm type for convergence test
    PC Object: (flow_sub_) 1 MPI processes
      type: ilu
      PC has not been set up so information may be incomplete
        out-of-place factorization
        0 levels of fill
        tolerance for zero pivot 2.22045e-14
        using diagonal shift on blocks to prevent zero pivot [INBLOCKS]
        matrix ordering: natural
      linear system matrix = precond matrix:
      Mat Object: (flow_) 1 MPI processes
        type: seqbaij
        rows=1389, cols=1389, bs=3
        total: nonzeros=20025, allocated nonzeros=20025
        total number of mallocs used during MatSetValues calls =0
            block size is 3
    - - - - - - - - - - - - - - - - - -

-- 
HeeHo Daniel Park
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