    FFTW is a free collection of fast C routines for computing the
    Discrete Fourier Transform in one or more dimensions.  It includes
    complex, real, symmetric, and parallel transforms, and can handle
    arbitrary array sizes efficiently.  FFTW is typically faster than
    other publically-available FFT implementations, and is even
    competitive with vendor-tuned libraries.  (See our web page
    http://fftw.org/ for extensive benchmarks.)  To achieve this
    performance, FFTW uses novel code-generation and runtime
    self-optimization techniques (along with many other tricks).

    The doc/ directory contains the manual in texinfo, PDF, info, and HTML
    formats.  Frequently asked questions and answers can be found in the
    doc/FAQ/ directory in ASCII and HTML.

    For a quick introduction to calling FFTW, see the "Tutorial" section
    of the manual.

    INSTALLATION
    ------------

    INSTALLATION FROM AN OFFICIAL RELEASE:

    Please read chapter 10 "Installation and Customization" of the manual.
    In short:

         ./configure
         make
         make install

    INSTALLATION FROM THE GIT REPOSITORY:

    First, install these programs:

      ocaml, ocamlbuild, autoconf, automake, indent, and libtool.

    You also need the ocaml Num library, which was standard in Ocaml but
    was removed without warning in OCaml 4.06.0 (3 Nov 2017).  On Fedora
    30, try installing the ocaml-num-devel package.

    Then, execute

        sh bootstrap.sh
        make

    The bootstrap.sh script runs configure directly, but if you need to
    re-run configure, you must pass the --enable-maintainer-mode flag:

        ./configure --enable-maintainer-mode [OTHER CONFIGURE FLAGS]

    Alternatively, you can run

        sh mkdist.sh

    which will run the entire bootstrapping process and generate
    .tar.gz files similar to those for official releases.

    CONTACTS
    --------

    FFTW was written by Matteo Frigo and Steven G. Johnson.  You can
    contact them at fftw@fftw.org.  The latest version of FFTW,
    benchmarks, links, and other information can be found at the FFTW home
    page (http://www.fftw.org).  You can also sign up to the fftw-announce
    Google group to receive (infrequent) updates and information about new
    releases.