[petsc-users] complex number issues

[RenZhengYong]

On Thu, May 20, 2010 at 8:54 PM, Barry Smith <bsmith at mcs.anl.gov> wrote:

>
> On May 20, 2010, at 7:24 AM, RenZhengYong wrote:
>
>
> On Wed, May 19, 2010 at 8:56 PM, Satish Balay <balay at mcs.anl.gov> wrote:
>
>> I don't understand the code change - but if you want to use c99
>> complex - you can build petsc with:
>>
>> --with-scalar-type=complex --with-clanguage=c [which is the default for
>> clanguage]
>>
>> And no code-change needed for PETSc. However if your code uses c++ -
>> you might have to address that..
>>
> Badly, my code uses C++.  I compiled PETSc with
> "--with-scalar-type=complex --with-clanguage=c" and I
> added
> include ${PETSC_DIR}/conf/variables
> include ${PETSC_DIR}/conf/rules
> in my makefile. So, could it possible to specify g++ for my code and to
> link c-version petsc?
>
>    So long as you do not use any C++ feature of PETSc you can do this. BUT
> C's complex numbers are C's and may not work with a C++ compiler. With C++
> code you may simply need to use the C++ complex type, this has nothing to do
> with PETSc.
>
> Several minutes ago, I successfully  linked the c-version petsc in my c++
code which uses C99 complex number.  I did not change anything, except for
writing a proper makefile to call petsc as a library, :). Now, it works.

  How do you know that C's complex is 50 times faster than C++'s? That is
> not our experience.
>
I wrote a small code which only has two loops. In the inner loop, there are
several complex-value based vector's operations such as  vector's product
and cross.  with "-O3" flag on, the code using C99 complex number is much
faster than C++'s complex class.  I do not know the reason either.




>     Barry
>
>
> kind regards,
> Zhengyong
>
>>
>> Satish
>>
>> On Wed, 19 May 2010, RenZhengYong wrote:
>>
>> > Hi,  PETSc team,
>> > I wrote a C++ code dealing with electromagnetic problems, which can
>> smoothly
>> > call PETSc complied by using " --with-scalar-type=complex
>> > --with-clanguage=cxx" .
>> > To improve the performances of the C++ code, I changed the complex
>> number of
>> > type from std::complex<double> to double _Complex (C99 standard, roughly
>> > 30~50 times faster compared to std::complex<double>). But when I find
>> that
>> > the C99 complex number head file <complex.h> will lead to the following
>> > kinds of errors"
>> >
>> > /usr/include/c++/4.3/complex:57: error: expected identifier before
>> > ‘__complex__’
>> > /usr/include/c++/4.3/complex:58: error: expected identifier before
>> > ‘__complex__’
>> > /usr/include/c++/4.3/complex:58: error: expected unqualified-id before
>> ‘<’
>> > token
>> > /usr/include/c++/4.3/complex:59: error: expected identifier before
>> > ‘__complex__’
>> > /usr/include/c++/4.3/complex:59: error: expected unqualified-id before
>> ‘<’
>> > token
>> > /usr/include/c++/4.3/complex:60: error: expected identifier before
>> > ‘__complex__’
>> > /home/Zhengyong/packages/petsc-3.1-p1/include/petscmath.h:157: error:
>> > expected unqualified-id before ‘__complex__’
>> > /home/Zhengyong/packages/petsc-3.1-p1/include/petscmath.h:306: error:
>> > ‘PetscScalar’ does not name a type
>> > /home/Zhengyong/packages/petsc-3.1-p1/include/petscmath.h:339: error:
>> > ‘PetscScalar’ does not name a type
>> > /home/Zhengyong/packages/petsc-3.1-p1/include/petscmath.h:469: warning:
>> > ‘PetscGlobalSum’ initialized and declared ‘extern’
>> > /home/Zhengyong/packages/petsc-3.1-p1/include/petscmath.h:469: error:
>> > ‘PetscScalar’ was not declared in this scope
>> > /home/Zhengyong/packages/petsc-3.1-p1/include/petscmath.h:469: error:
>> > expected primary-expression before ‘,’ token
>> > /home/Zhengyong/packages/petsc-3.1-p1/include/petscmath.h:469: error:
>> > ‘PetscScalar’ was not declared in this scope
>> > /home/Zhengyong/packages/petsc-3.1-p1/include/petscmath.h:469: error:
>> > expected primary-expression before ‘,’ token
>> > /home/Zhengyong/packages/petsc-3.1-p1/include/petscmath.h:469: error:
>> > expected primary-expression before ‘)’ token
>> > /home/Zhengyong/packages/petsc-3.1-p1/include/petscmath.h:469: error:
>> > initializer expression list treated as compound expression
>> >
>> >
>> > Could you please give me some idea to deal with these problems?
>> >
>> > Kind regards,
>> > Zhengyong Ren
>> >
>> >
>>
>
>
>
> --
> Zhengyong Ren
> AUG Group, Institute of Geophysics
> Department of Geosciences, ETH Zurich
> NO H 47 Sonneggstrasse 5
> CH-8092, Zürich, Switzerland
> Tel: +41 44 633 37561
> e-mail: zhengyong.ren at aug.ig.erdw.ethz.ch
> Gmail: renzhengyong at gmail.com
>
>
>


-- 
Zhengyong Ren
AUG Group, Institute of Geophysics
Department of Geosciences, ETH Zurich
NO H 47 Sonneggstrasse 5
CH-8092, Zürich, Switzerland
Tel: +41 44 633 37561
e-mail: zhengyong.ren at aug.ig.erdw.ethz.ch
Gmail: renzhengyong at gmail.com
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