On Mon, 12 Jan 2009 19:43:00 +0100 "Bas van Dijk" <v.dijk....@gmail.com> wrote:
> On Mon, Jan 12, 2009 at 6:47 PM, Max Bolingbroke > <batterseapo...@hotmail.com> wrote: > > GHC should indeed be doing so. I'm working (on and off) to work out > > some suitable heuristics and put the transformation into ghc -O2. > > There are a few wrinkles that still need sorting out, but > > preliminary indications are that it decreases the runtime of our > > standard benchmark suite, nofib, by 12% or so. > > Great! > > In the Stream library I'm developing at http://code.haskell.org/Stream > I 'closurize' (for lack of a better name) all my functions. Here are a > few random examples: > > repeat :: a -> Stream a > repeat x = repeat_x > where > repeat_x = x ::: repeat_x > > cycle :: [a] -> Stream a > cycle xs = cycle_xs > where > cycle_xs = foldr (:::) cycle_xs xs > > deleteBy :: (a -> a -> Bool) -> a -> Stream a -> Stream a > deleteBy eq x = deleteBy_eq_x > where > deleteBy_eq_x (y ::: ys) > | eq x y = ys > | otherwise = y ::: deleteBy_eq_x ys > > Closurizing the functions in Data.Stream lead to 10% to 250% speedups! Awesome! I tend to use Control.Monad.Fix.fix (which actually has nothing to do with monads, despite the package name) sometimes, for "closurizing" a recursive function. I am curious as to whether the "fix" style of recursive programming is likely to result in the same speedups. The fix-style equivalent to your repeat above, would be something like this: repeat x = fix $ \me -> x ::: me (I use "me" for the name of the recursive call, partly because it reminds me that it's a self-call, and partly because I find it amusing) -- Robin _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
