cannam@95: Previous: Cycle Counters, cannam@95: Up: Installation and Customization cannam@95:
cannam@95: The directory genfft contains the programs that were used to
cannam@95: generate FFTW's “codelets,” which are hard-coded transforms of small
cannam@95: sizes.
cannam@95: We do not expect casual users to employ the generator, which is a rather
cannam@95: sophisticated program that generates directed acyclic graphs of FFT
cannam@95: algorithms and performs algebraic simplifications on them. It was
cannam@95: written in Objective Caml, a dialect of ML, which is available at
cannam@95: http://caml.inria.fr/ocaml/index.en.html.
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If you have Objective Caml installed (along with recent versions of
cannam@95: GNU autoconf, automake, and libtool), then you
cannam@95: can change the set of codelets that are generated or play with the
cannam@95: generation options. The set of generated codelets is specified by the
cannam@95: {dft,rdft}/{codelets,simd}/*/Makefile.am files. For example, you can add
cannam@95: efficient REDFT codelets of small sizes by modifying
cannam@95: rdft/codelets/r2r/Makefile.am.
cannam@95: After you modify any Makefile.am files, you can type sh
cannam@95: bootstrap.sh in the top-level directory followed by make to
cannam@95: re-generate the files.
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We do not provide more details about the code-generation process, since cannam@95: we do not expect that most users will need to generate their own code. cannam@95: However, feel free to contact us at fftw@fftw.org if cannam@95: you are interested in the subject. cannam@95: cannam@95:
You might find it interesting to learn Caml and/or some modern cannam@95: programming techniques that we used in the generator (including monadic cannam@95: programming), especially if you heard the rumor that Java and cannam@95: object-oriented programming are the latest advancement in the field. cannam@95: The internal operation of the codelet generator is described in the cannam@95: paper, “A Fast Fourier Transform Compiler,” by M. Frigo, which is cannam@95: available from the FFTW home page and also cannam@95: appeared in the Proceedings of the 1999 ACM SIGPLAN Conference on cannam@95: Programming Language Design and Implementation (PLDI). cannam@95: cannam@95: cannam@95: