[petsc-users] Solving Linear Systems with Scalar Real and Complex

[Matthew Knepley]

On Fri, Jul 20, 2018 at 8:01 AM Pierpaolo Minelli <pierpaolo.minelli at cnr.it>
wrote:

> Hi,
>
> in my code I have to solve both a system in the field of real numbers and
> in the field of complex numbers.
> My approach has been as follows.
> First I configured PETSc with the --with-scalar-type=complex option.
> Using this option I have unfortunately lost the possibility to use the two
> preconditioners ML and Hypre.
> I later created two subspaces of Krylov and tried to solve the two systems
> as I used to when solving the only equation in the real numbers field.
> In order to correctly solve the system in the field of real numbers I had
> to transform the coefficients from real to complex with an imaginary part
> equal to zero.
>
> Is there a possibility to use a different and better approach to solve my
> problem?
>
> Perhaps an approach where you can continue to use ML and Hypre for system
> solving in the real numbers field or where you don't need to use complex
> numbers when real numbers would actually suffice?
>

Yes, any linear system in complex numbers can be converted to a system
twice as large in real numbers. So far,
I think this is the best way to handle it, especially the elliptic ones.

  Thanks,

     Matt


> Thanks in advance
>
> Pierpaolo
>
>

-- 
What most experimenters take for granted before they begin their
experiments is infinitely more interesting than any results to which their
experiments lead.
-- Norbert Wiener

https://www.cse.buffalo.edu/~knepley/ <http://www.caam.rice.edu/~mk51/>
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