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

[Chetan Jhurani]

I've faced similar issues with std::complex, but the material below,

which is not in the C++ standard, has suppressed my fears.  Not

eliminated though.

 

http://fftw.org/doc/Complex-numbers.html (has a broken link, corrected below)

http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2002/n1388.pdf

 

Chetan

 

From: petsc-users-bounces at mcs.anl.gov [mailto:petsc-users-bounces at mcs.anl.gov] On Behalf Of Jack Poulson
Sent: Tuesday, February 07, 2012 10:10 AM
To: PETSc users list
Subject: Re: [petsc-users] one compilation error in PETSc-dev with enabling GPU and complex number

 

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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