[petsc-users] Binary format in real vs. complex scalar type configurations

[Matthew Knepley]

On Tue, May 11, 2021 at 12:03 PM Pierre Jolivet <pierre at joliv.et> wrote:

> Hello Frederico,
> I’m not sure that’s possible.
> Here is what I do, it makes me sick, but mixing precisions/scalar types
> with PETSc is difficult (crossing my fingers this will be better with
> future).
> In MATLAB (after putting petsc/share/petsc/matlab in the path):
> A = PetscBinaryRead('your_binary_mat_with_re+im.dat','complex',true); %
> scalar-type=complex
> PetscBinaryWrite('re.dat',real(A)); % scalar-type=real
> PetscBinaryWrite('im.dat',imag(A)); % scalar-type=real
>

So what you want to happen is that MatLoad() looks at the datatype, sees
that it is complex and PetscScalar is real, and returns two matrices with
the real and imaginary parts?

The hard part is that the MatLoad interface returns a single matrix. I
guess we could have a flag that says what to do with complex numbers (read
real, read imaginary, read norm, etc.)
and you could read it twice. Would that work?

  Thanks,

     Matt


> Thanks,
> Pierre
>
> On 11 May 2021, at 3:30 PM, Frederico Teixeira <teixeira at zmt.swiss> wrote:
>
> Dear fellows,
>
> I hope this message finds you safe and well.
>
> I have a complex-valued matrix and its real/imaginary components in binary
> format. They were extracted from a solver that only works with
> "scalar-type=complex" configuration.
> I am getting weird results when I load them into a small test program
> that's configured with "scalar-type=real", but I believe this is expected.
> At the end of the day, I would like to have both real and imaginary
> components as real-valued matrices.
> Is it possible to do it? I want to test preconditioners that are tailored
> for this sort of problem.
>
> Regards,
>  Frederico.
>
>
>

-- 
What most experimenters take for granted before they begin their
experiments is infinitely more interesting than any results to which their
experiments lead.
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https://www.cse.buffalo.edu/~knepley/ <http://www.cse.buffalo.edu/~knepley/>
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