view Lib/fftw-3.2.1/genfft/littlesimp.ml @ 1:e86e9c111b29

Updates stuff that potentially fixes the memory leak and also makes it work on Windows and Linux (Need to test). Still have to fix fftw include for linux in Jucer.

(*
 * Copyright (c) 1997-1999 Massachusetts Institute of Technology
 * Copyright (c) 2003, 2007-8 Matteo Frigo
 * Copyright (c) 2003, 2007-8 Massachusetts Institute of Technology
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *
 *)

(* 
 * The LittleSimplifier module implements a subset of the simplifications
 * of the AlgSimp module.  These simplifications can be executed
 * quickly here, while they would take a long time using the heavy
 * machinery of AlgSimp.  
 * 
 * For example, 0 * x is simplified to 0 tout court by the LittleSimplifier.
 * On the other hand, AlgSimp would first simplify x, generating lots
 * of common subexpressions, storing them in a table etc, just to
 * discard all the work later.  Similarly, the LittleSimplifier
 * reduces the constant FFT in Rader's algorithm to a constant sequence.
 *)

open Expr

let rec makeNum = function
  | n -> Num n

and makeUminus = function
  | Uminus a -> a 
  | Num a -> makeNum (Number.negate a)
  | a -> Uminus a

and makeTimes = function
  | (Num a, Num b) -> makeNum (Number.mul a b)
  | (Num a, Times (Num b, c)) -> makeTimes (makeNum (Number.mul a b), c)
  | (Num a, b) when Number.is_zero a -> makeNum (Number.zero)
  | (Num a, b) when Number.is_one a -> b
  | (Num a, b) when Number.is_mone a -> makeUminus b
  | (Num a, Uminus b) -> Times (makeUminus (Num a), b)
  | (a, (Num b as b')) -> makeTimes (b', a)
  | (a, b) -> Times (a, b)

and makePlus l = 
  let rec reduceSum x = match x with
    [] -> []
  | [Num a] -> if Number.is_zero a then [] else x
  | (Num a) :: (Num b) :: c -> 
      reduceSum ((makeNum (Number.add a b)) :: c)
  | ((Num _) as a') :: b :: c -> b :: reduceSum (a' :: c)
  | a :: s -> a :: reduceSum s

  in match reduceSum l with
    [] -> makeNum (Number.zero)
  | [a] -> a 
  | [a; b] when a == b -> makeTimes (Num Number.two, a)
  | [Times (Num a, b); Times (Num c, d)] when b == d ->
      makeTimes (makePlus [Num a; Num c], b)
  | a -> Plus a