[petsc-users] Solving a linear system with symmetrical matrix

[Barry Smith]

On Mar 24, 2011, at 5:26 AM, Longmin RAN wrote:

> Hello everyone,
> 
> 
> I use superlu inside petsc to solve linear systems with symmetrical
> matrix. The solving time is at least twice longer than using superlu
> directly.

   How much of that time is in other parts of the code, not the actual superlu solver? Run the PETSc version with -log_summary; the times given in the lines
MatFactorSymbolic, MatFactorNumerical, MatSolve (or some similar names) are the amount of time in Superlu. Compare those times to the superlu standalone solution time.

    Did you ./configure PETSc with the option --with-debugging=0?

   Barry

 

> Since I'm new with Petsc, I didn't fine-tune much the petsc
> solver, as I had done when using superlu directly. For example, in
> superlu there are options like diagonal pivot
> threshold(superlu_options_t.DiagPivotThresh), symmetric mode
> (superlu_options_t.SymmetricMode), and column
> permutation(superlu_options_t.ColPerm). Could anybody inform me about
> the corresponding options in petsc? Thanks in advance.
> 
> BTW, I tried the following options:
> 	MatSetOption(A, MAT_SYMMETRIC, PETSC_TRUE);
> 	MatSetOption(A, MAT_SYMMETRY_ETERNAL, PETSC_TRUE);
> But it seems that these options weren't enough to reduce the solving
> time sufficiently.
> 
> 
> Best regards,
> 
> - Longmin Ran