[petsc-users] Newbie question : iterative solver - algorithm and performance

[Barry Smith]

> On Feb 15, 2017, at 7:03 AM, lixin chu <lixin_chu at yahoo.com> wrote:
> 
> I think the chapter 4 of the user manual more or less answers my first question already ...
>  
> rgds
> lixin
> 
> 
> On Wednesday, 15 February 2017, 14:40, lixin chu <lixin_chu at yahoo.com> wrote:
> 
> 
> Hello,
> New to PETSc, appreciate any help - 
> 
> I have done some experiment with MUMPS (the direct solver for sparse matrix), and very interested to try out PETSc now. I have a large sparse symmetric matrix (3 millions x 3 millions, complex data type).
> 
> Some questions I have:
> - I am assuming that I should select one algorithm of "Krylov methods", which algorithm is a good option, GMRES, CG, or others ? (I am not a domain expert, but helping developing a program to test the matrix). 

   GMRES is a "safe" choice. You can try -ksp_type cg   -ksp_cg_type symmetric  (or if the matrix is hermitian; i.e. transpose A = complex conjugate of A  then type hermitian instead of symmetric).


> - do all the algorithms support distributed architecture (multiple machines, multiple cores)

    Yes

> - are there any performance test data ? (total run time for example)

   Run your code with -view_summary and it will print information at the end about where it has spent the time doing the computation. 


> 
>  
> thank you very much,
> LX
> 
>