On Wed, 6 Sep 2017, Michael Gegg wrote:

Hello everyone,

a while ago I wrote about a patch for petsc with complex number c++ and float128 using c99 complex numbers and you suggested to just use petsc with a c build and then just call it from c++ (see below).

I thought that this worked, but I only tried it for my patched version. Now I tried to do this for the normal v3.7.6 and I get a lot of errors that PetscCompex is not defined when I call it from c++. The installation works fine and also the tutorial examples. (which are all c)

It seems that if I call petsc from c++ it tries to switch to c++ complex numbers even though I build petsc with c, which are obviously not defined.

Yes - because a c++ user would want to use c++/complex from their c++ code [even if petsc is buit with c]

So, could you give me a hint on how I should configure petsc so that this works? Is there a way to enforce the c99 complex numbers even when calling petsc from c++?

Perhaps this is the change you need? [untested] diff --git a/include/petscmath.h b/include/petscmath.h index a63f1f4977..311d10f081 100644 --- a/include/petscmath.h +++ b/include/petscmath.h @@ -214,7 +214,7 @@ PETSC_EXTERN MPI_Datatype MPIU___COMPLEX128; #endif /* PETSC_USE_REAL_ */ #endif /* ! PETSC_SKIP_COMPLEX */ -#elif !defined(__cplusplus) && defined(PETSC_HAVE_C99_COMPLEX) && !defined(PETSC_USE_REAL___FP16) +#elif defined(PETSC_HAVE_C99_COMPLEX) && !defined(PETSC_USE_REAL___FP16) #if !defined(PETSC_SKIP_COMPLEX) #define PETSC_HAVE_COMPLEX 1 #include <complex.h>

I always used

./configure ... --with-cc=gcc --with-cxx=g++ --with-fc=gfortran --download-mpich --with-clanguage=c --with-scalar-type=complex --with-precision=__float128 --download-f2cblaslapack

As I said, with my patch this works fine. Thanks in advance.

Also I realized that parmetis does only support double and not float128 and so building petsc with float128 and parmetis crashes. I also made a patch for that, that just declares all parmetis relevant parameters as real_t instead of PetscReal. Would you be interested in including this patch? (its only 2 lines)

Thank you.

Michael

Am 03.05.2017 um 18:08 schrieb Michael Gegg:

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Am 03.05.2017 um 16:27 schrieb Matthew Knepley:

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On Wed, May 3, 2017 at 9:22 AM, Michael Gegg <[email protected] <mailto:[email protected]>> wrote:

Hello Petsc developers,

thank you for providing such a marvellous numerics package, we had/have a lot of fun using it. For our purposes it was necessary to use Petsc with c++, float128 and complex. Since this is not possible with the standard build we made a patch. It uses c style complex numbers as a workaround. It can be used with the Parmetis package (there is a little fix in the interface there) and we have made a Slepc patch that then also allows to use c++, float128 and complex. It would be great if you could include it in the petsc software. We checked the patch for v3.7.6 and v3.7.3 (latest Slepc release)

One question. Why would you compile PETSc with C++ if you wanted to use C99 complex? You can do that with the C build, and call PETSc the same way from C++.

No specific reason. Thanks for the hint, I tried it and it works. I could have saved some effort there, but I also learned a thing or two ;) I just didn't know that this was possible. Thanks, Michael

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Thanks,

Matt

With best regards,

Michael Gegg

-- 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