[petsc-dev] fortran literals

Thu Sep 1 22:24:57 CDT 2016

It's Fortran 2008 but I don't know any respectable compiler that doesn't
support it. It works with Intel, GCC and Cray. Probably IBM XLF too, but
I've not tested. Not sure about any others. I think it's possible to
emulate it if necessary.

Jeff

On Thursday, September 1, 2016, Blaise A Bourdin <bourdin at lsu.edu> wrote:

> Neat.
> I was not aware of this.
>
> Blaise
>
> > On Sep 1, 2016, at 9:26 PM, Jeff Hammond <jeff.science at gmail.com
> <javascript:;>> wrote:
> >
> > https://gcc.gnu.org/onlinedocs/gfortran/ISO_005fFORTRAN_005fENV.htmlhas
> real{32,64,128} that does a nice job for this situation.
> >
> > Jeff
> >
> > Sent from my iPhone
> >
> >> On Sep 1, 2016, at 4:15 PM, Blaise A Bourdin <bourdin at lsu.edu
> <javascript:;>> wrote:
> >>
> >> Hi,
> >>
> >> If I recall correctly, fortran does not mandate that
> "selected_real_kind(5)" means the same across compilers, so that hardcoding
> kind values may not be portable.
> >>
> >>
> >> Instead, I would recommend the following (not my idea, it was proposed
> by Michael Metcalf in comp.lang.fortran a _long_ time ago) in a top-level
> module.
> >>
> >>  ! The following ensures that mef90 and PETSC real types are compatible:
> >>  ! thanks to Michael Metcalf in comp.lang.fortran
> >>  PetscReal,Parameter                 :: PReal = 1.0
> >>  Integer,Parameter,Public            :: Kr =
> Selected_Real_Kind(Precision(PReal))
> >>
> >>  PetscInt,Parameter                  :: PInt = 1
> >>  Integer,Parameter,Public            :: Ki = Selected_Int_Kind(PInt)
> >>
> >>  PetscLogDouble,Parameter            :: flop = 1.0
> >>  Integer,Parameter,Public            :: PFlop =
> Selected_Real_Kind(Precision(flop))
> >>
> >> so that Real(Kind = Kr) is the same as PetscReal, and literals can be
> written 1.234_Kr or 23_flop.
> >>
> >> I guess PETSc could define them in the petsc module and inherited from
> "use petsc”.
> >>
> >> Blaise
> >>
> >>
> >>
> >>> On Sep 1, 2016, at 5:37 PM, Barry Smith <bsmith at mcs.anl.gov
> <javascript:;>> wrote:
> >>>
> >>>
> >>>> On Sep 1, 2016, at 5:28 PM, Munson, Todd <tmunson at mcs.anl.gov
> <javascript:;>> wrote:
> >>>>
> >>>>
> >>>> Which platforms do not define PETSC_USE_FORTRANKIND?
> >>>
> >>> It uses it everywhere the Fortran compiler supports it.
> >>>
> >>> # reverse of the above - but more standard thing to do for F90
> compilers
> >>> def checkFortranKind(self):
> >>>  '''Checks whether selected_int_kind etc work USE_FORTRANKIND'''
> >>>  self.pushLanguage('FC')
> >>>  body = '''
> >>>      integer(kind=selected_int_kind(10)) i
> >>>      real(kind=selected_real_kind(10)) d
> >>> '''
> >>>  if self.checkCompile('', body):
> >>>    self.addDefine('USE_FORTRANKIND', 1)
> >>>  self.popLanguage()
> >>>  return
> >>>
> >>> Presumably any Fortran compiler that supports F90 supports it so it is
> not unreasonable for us to just require it and simplify PETSc in a few
> places.
> >>>
> >>>
> >>>
> >>>
> >>>> Are they important
> >>>> or can we drop support for them?
> >>>>
> >>>> I could probably hack the D or Q for the others, but it would probably
> >>>> be ugly.
> >>>>
> >>>> Or I could just overrule my OCD today...
> >>>>
> >>>> Todd.
> >>>>
> >>>>> On Sep 1, 2016, at 5:08 PM, Barry Smith <bsmith at mcs.anl.gov
> <javascript:;>> wrote:
> >>>>>
> >>>>>
> >>>>>> On Sep 1, 2016, at 4:37 PM, Munson, Todd <tmunson at mcs.anl.gov
> <javascript:;>> wrote:
> >>>>>>
> >>>>>>
> >>>>>> Cool!
> >>>>>>
> >>>>>> For what its worth, that only works when PETSC_USE_FORTRANKIND is
> true.
> >>>>>> I'm not sure how many of the Petsc builds have this flag set.
> >>>>>
> >>>>> in the other case could you try to tack on the D or Q business?
> >>>>>
> >>>>> Barry
> >>>>>
> >>>>>>
> >>>>>> Any idea how to do the same thing in C?
> >>>>>>
> >>>>>> Todd.
> >>>>>>
> >>>>>>> On Sep 1, 2016, at 4:13 PM, Lisandro Dalcin <dalcinl at gmail.com
> <javascript:;>> wrote:
> >>>>>>>
> >>>>>>>
> >>>>>>> On 1 September 2016 at 23:05, Barry Smith <bsmith at mcs.anl.gov
> <javascript:;>> wrote:
> >>>>>>> I didn't have a solution to this
> >>>>>>>
> >>>>>>> ! These lines should be added to $PETSC_DIR/include/petsc/
> finclude/petscsysdef.h
> >>>>>>> #if defined(PETSC_USE_REAL_SINGLE)
> >>>>>>> integer, parameter :: PETSC_REAL_KIND = selected_real_kind(5)
> >>>>>>> #elif defined(PETSC_USE_REAL_DOUBLE)
> >>>>>>> integer, parameter :: PETSC_REAL_KIND = selected_real_kind(10)
> >>>>>>> #elif defined(PETSC_USE_REAL___FLOAT128)
> >>>>>>> integer, parameter :: PETSC_REAL_KIND = selected_real_kind(20)
> >>>>>>> #endif
> >>>>>>>
> >>>>>>> ! User code should write literals this way
> >>>>>>> PetscReal x
> >>>>>>> x = 0.123456789123456789123456789_PETSC_REAL_KIND
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>> --
> >>>>>>> Lisandro Dalcin
> >>>>>>> ============
> >>>>>>> Research Scientist
> >>>>>>> Computer, Electrical and Mathematical Sciences & Engineering
> (CEMSE)
> >>>>>>> Extreme Computing Research Center (ECRC)
> >>>>>>> King Abdullah University of Science and Technology (KAUST)
> >>>>>>> http://ecrc.kaust.edu.sa/
> >>>>>>>
> >>>>>>> 4700 King Abdullah University of Science and Technology
> >>>>>>> al-Khawarizmi Bldg (Bldg 1), Office # 0109
> >>>>>>> Thuwal 23955-6900, Kingdom of Saudi Arabia
> >>>>>>> http://www.kaust.edu.sa
> >>>>>>>
> >>>>>>> Office Phone: +966 12 808-0459
> >>
> >> --
> >> Department of Mathematics and Center for Computation & Technology
> >> Louisiana State University, Baton Rouge, LA 70803, USA
> >> Tel. +1 (225) 578 1612, Fax  +1 (225) 578 4276
> http://www.math.lsu.edu/~bourdin
> >>
> >>
> >>
> >>
> >>
> >>
> >>
>
> --
> Department of Mathematics and Center for Computation & Technology
> Louisiana State University, Baton Rouge, LA 70803, USA
> Tel. +1 (225) 578 1612, Fax  +1 (225) 578 4276 http://www.math.lsu.edu/~
> bourdin
>
>
>
>
>
>
>
>

-- 
Jeff Hammond
jeff.science at gmail.com
http://jeffhammond.github.io/
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