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7.1.1 Extended and quadruple precision in Fortran
If FFTW is compiled in long double
(extended) precision
(see section Installation and Customization), you may be able to call the
resulting fftwl_
routines (see section Precision) from Fortran if
your compiler supports the C_LONG_DOUBLE_COMPLEX
type code.
Because some Fortran compilers do not support
C_LONG_DOUBLE_COMPLEX
, the fftwl_
declarations are
segregated into a separate interface file fftw3l.f03
, which you
should include in addition to fftw3.f03
(which declares
precision-independent ‘FFTW_’ constants):
use, intrinsic :: iso_c_binding include 'fftw3.f03' include 'fftw3l.f03'
We also support using the nonstandard __float128
quadruple-precision type provided by recent versions of gcc
on
32- and 64-bit x86 hardware (see section Installation and Customization),
using the corresponding real(16)
and complex(16)
types
supported by gfortran
. The quadruple-precision ‘fftwq_’
functions (see section Precision) are declared in a fftw3q.f03
interface file, which should be included in addition to
fftw3l.f03
, as above. You should also link with
-lfftw3q -lquadmath -lm
as in C.
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