[petsc-users] one compilation error in PETSc-dev with enabling GPU and complex number

[Jack Poulson]

On Tue, Feb 7, 2012 at 11:29 AM, Matthew Knepley <knepley at gmail.com> wrote:

> On Tue, Feb 7, 2012 at 11:20 AM, recrusader <recrusader at gmail.com> wrote:
>
>> Whether is it possible to find an efficient mechanism to do the
>> conversion between std::complex and cusp::complex when the conversion is
>> necessary.
>>
>
> That does not matter. This is a compile error. We are not going to change
> this right now, and it seems like you are not going
> make the necessary changes, so I would say that complex numbers are not
> supported with our GPU code right now. The
> change would involve using cusp::complex for PetscScalar, and I am not
> sure how much work that would entail.
>
>    Matt
>

Matt,

You might be interested to hear that the C++03 standard states that "The
effect of instantiating the template complex for any type other than float,
double or long double is unspecified". Thus, complex quad precision with it
is probably a bad idea and, if I'm not mistaken, the standard does not
state that the class must store data in the form

double real, imag;

so this could potentially break interfaces (e.g., to BLAS or LAPACK). Maybe
it would be worthwhile to avoid usage of std::complex and simultaneously
fix the compatibility issue with cusp::complex. I recently ripped
std::complex out of Elemental for the above reasons.

Jack
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