cannam@95: cannam@95: cannam@95: Extended and quadruple precision in Fortran - FFTW 3.3.3 cannam@95: cannam@95: cannam@95: cannam@95: cannam@95: cannam@95: cannam@95: cannam@95: cannam@95: cannam@95: cannam@95: cannam@95: cannam@95:
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7.1.1 Extended and quadruple precision in Fortran

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cannam@95: If FFTW is compiled in long double (extended) precision cannam@95: (see Installation and Customization), you may be able to call the cannam@95: resulting fftwl_ routines (see Precision) from Fortran if cannam@95: your compiler supports the C_LONG_DOUBLE_COMPLEX type code. cannam@95: cannam@95:

Because some Fortran compilers do not support cannam@95: C_LONG_DOUBLE_COMPLEX, the fftwl_ declarations are cannam@95: segregated into a separate interface file fftw3l.f03, which you cannam@95: should include in addition to fftw3.f03 (which declares cannam@95: precision-independent ‘FFTW_’ constants): cannam@95: cannam@95:

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       use, intrinsic :: iso_c_binding
cannam@95:        include 'fftw3.f03'
cannam@95:        include 'fftw3l.f03'
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We also support using the nonstandard __float128 cannam@95: quadruple-precision type provided by recent versions of gcc on cannam@95: 32- and 64-bit x86 hardware (see Installation and Customization), cannam@95: using the corresponding real(16) and complex(16) types cannam@95: supported by gfortran. The quadruple-precision ‘fftwq_’ cannam@95: functions (see Precision) are declared in a fftw3q.f03 cannam@95: interface file, which should be included in addition to cannam@95: fftw3l.f03, as above. You should also link with cannam@95: -lfftw3q -lquadmath -lm as in C. cannam@95: cannam@95: cannam@95: cannam@95: