Precision - FFTW 3.3.3

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4.1.2 Precision

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cannam@95: You can install single and long-double precision versions of FFTW, cannam@95: which replace double with float and long double, cannam@95: respectively (see Installation and Customization). To use these cannam@95: interfaces, you: cannam@95: cannam@95:

Link to the single/long-double libraries; on Unix, -lfftw3f or cannam@95: -lfftw3l instead of (or in addition to) -lfftw3. (You cannam@95: can link to the different-precision libraries simultaneously.) cannam@95: cannam@95:
Include the same <fftw3.h> header file. cannam@95: cannam@95:
Replace all lowercase instances of ‘fftw_’ with ‘fftwf_’ or cannam@95: ‘fftwl_’ for single or long-double precision, respectively. cannam@95: (fftw_complex becomes fftwf_complex, fftw_execute cannam@95: becomes fftwf_execute, etcetera.) cannam@95: cannam@95:
Uppercase names, i.e. names beginning with ‘FFTW_’, remain the cannam@95: same. cannam@95: cannam@95:
Replace double with float or long double for cannam@95: subroutine parameters. cannam@95: cannam@95:

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Depending upon your compiler and/or hardware, long double may not cannam@95: be any more precise than double (or may not be supported at all, cannam@95: although it is standard in C99). cannam@95: cannam@95: cannam@95:

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: To use this type, link with -lfftw3q -lquadmath -lm (the cannam@95: libquadmath library provided by gcc is needed for cannam@95: quadruple-precision trigonometric functions) and use ‘fftwq_’ cannam@95: identifiers. cannam@95: cannam@95: cannam@95: cannam@95: