Re: [Haskell-cafe] Memory Management and Lists

On 07/11/2016 11:56 AM, David Feuer wrote:

Please repost your code, giving a type signature for each top-level binding. Without them, the code is very difficult to follow. I also strongly recommend using a newtype for your custom monad. Something like this:

{-# LANGUAGE GeneralizedNewtypeDeriving, MultiParamTypeClasses, StandaloneDeriving, ... #-}

newtype StateReader s c a = SR {runSR :: StateT s (Reader c) a} deriving (Functor, Applicative, Monad)

deriving instance MonadReader c (StateReader s c) deriving instance MonadState s (StateReader s c)

On Jul 11, 2016 11:07 AM, "Christopher Howard" mailto:ch.howard@zoho.com> wrote:

-- I'm a bit embarrassed of this code because I haven't yet optimized -- the 'stamp' algorithm for reduced number of matrix operations. But -- even in this state I should think the memory requirements shouldn't -- exceed 1MB while generating the nth Matrix, unless Matrix n-1, n-2, -- etc. are being preserved in memory unnecessarily.

-- Monad Stack

type StateReader s c a = StateT s (Reader c) a

evalStateReader m s c = (runReader (evalStateT m s)) c

-- Helper function

type Point = (Float, Float) type Metric = Point -> Point -> Float

euclidean :: Metric euclidean (x1, y1) (x2, y2) = sqrt ((x2 - x1)**2 + (y2 - y1)**2)

stamp :: StateReader (Matrix Float, [Point]) Float (Matrix Float, [Point])

-- monadic function. haven't had chance yet to optimize algorithm to -- reduce number of matrix operations

stamp = do radius <- ask (oMatrix, walk) <- get (wX, wY) <- (return . head) walk let nMatrix = matrix (nrows oMatrix) (ncols oMatrix) (\(x, y) -> let (x', y') = (fromIntegral x, fromIntegral y) in if euclidean (x', y') (wX, wY) > radius then getElem x y oMatrix else getElem x y oMatrix + 1) in put (nMatrix, tail walk) >> get

-- sequences and gathers results as list

stampingStates :: Matrix Float -> Float -> [Point] -> [Matrix Float]

stampingStates initMx radius walk = map fst $ evalStateReader (sequence (repeat stamp)) (initMx, walk) radius

-- Some quick experimentation code. h is the list

h :: [Matrix Float] intensityG :: Picture displayIntensityG :: IO ()

h = stampingStates initMx radius walk' where initMx = zero 250 250 radius = 40 walk' = walk 40 (125, 125) (mkStdGen 31415)

-- get 2001st Matrix and convert to Gloss Picture, employing -- some color interpretation code

intensityG = let mx = head (drop 2000 h) in toImage mx (lightnessInt 272 (minMax mx))

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