You can install single and long-double precision versions of FFTW,
respectively (see Installation and Customization). To use these
-lfftw3linstead of (or in addition to)
-lfftw3. (You can link to the different-precision libraries simultaneously.)
long doublefor subroutine parameters.
Depending upon your compiler and/or hardware,
long double may not
be any more precise than
double (or may not be supported at all,
although it is standard in C99).
We also support using the nonstandard
quadruple-precision type provided by recent versions of
32- and 64-bit x86 hardware (see Installation and Customization).
To use this type, link with
-lfftw3q -lquadmath -lm (the
libquadmath library provided by
gcc is needed for
quadruple-precision trigonometric functions) and use ‘fftwq_’