>
>
> I modify the step-17 so that it uses PETScWrappers::SparseDirectMUMPS as 
> solver. However, when I active the option of set_symmetric_mode, the 
> solution has discrepancy from CG or MUMPS without the symmetry option. (The 
> solutions from CG and MUMPS without symmetry option are identical though.) 
> Any suggestion?
>

Which version of PETSc, MUMPS and deal.II do you use? What is the matrix 
size you work with? 
 

>
> And it seems to me that  PETScWrappers::SparseDirectMUMPS doesn't have the 
> functionality of reusing the factorization of system matrix for different 
> right-hand side vector. Do I miss anything?
>

Yes, it does. The first time you call solve it performs factorization, but 
the following calls will reuse it (since you don't call KSPSetOperators). 
 

>
> Thank you very much.
>
> Best,
> Shanglong
>

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