[petsc-users] Is matrix analysis available in PETSc or external package?

[Danyang Su]

On 15-05-11 07:19 PM, Hong wrote:
> Danyang:
>
>
>     I recently have some time-dependent cases that have difficulty in
>     convergence. It needs a lot of linear iterations during a specific
>     time, e.g., more than 100 linear iterations for every newton
>     iteration. In PETSc parallel version, this number will be doubled
>     or even more. Our case usually needs less than 10 iterations for
>     every newton iteration. This is NOT caused by PETSc relative
>     routines as the original sequential solver (ILU) also has the same
>     problem.
>
>     The results seems reasonable, but the large number of iterations
>     leads me to suspect that something is not well implemented in a
>     particular module. This module is developed a long time ago by
>     another guy and it sounds impossible for me to check every line
>     (thousands of lines) and do theoretical analysis.Does PETSc or
>     external package provide matrix analysis to help to locate the
>     'suspected' entry?
>
> We need know what solvers being used. My guess is the default
> gmres/bjacobi/ilu(0). Please run your code with option '-ts_view' or 
> '-snes_view' to find out.
Hi Hong,

Sorry for the late reply. I guess there is nothing wrong in the solver 
or data structure, but maybe some large entries in the linear system 
that cause the problem hard to solve. I will export the matrix to check 
these values.

Thanks,

Danyang
>
> Hong
>

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