Shootout/Binary trees

Proposals

Float out the constant depth in sumT (worker/wrapper).

This short change to sumT massively reduces allocations and improves performance, despite being an obvious static argument transformation.

Explain what GHC is able to save work on here.

Before:

sumT :: Int -> Int -> Int -> Int
sumT d 0 t = t
sumT d i t = sumT d (i-1) (t + a + b)
  where
    a = check (make i    d)
    b = check (make (-i) d)

After:

sumT :: Int -> Int -> Int -> Int
sumT d i t = go i t 
  where
    go 0 t = t
    go i t = go (i-1) (t + a + b)

    a = check (make i    d)
    b = check (make (-i) d)

Complete:

{-# OPTIONS -fbang-patterns -funbox-strict-fields #-}
--
-- The Computer Language Shootout
-- http://shootout.alioth.debian.org/
--
-- Contributed by Don Stewart and Thomas Davie
--
-- This implementation uses a parallel strategy to exploit the quad core machine.
-- For more information about Haskell parallel strategies, see,
--
--  http://www.macs.hw.ac.uk/~dsg/gph/papers/html/Strategies/strategies.html
--

import System
import Data.Bits
import Text.Printf
import Control.Parallel.Strategies
import Control.Parallel

--
-- an artificially strict tree.
--
-- normally you would ensure the branches are lazy, but this benchmark
-- requires strict allocation.
--
data Tree = Nil | Node !Int !Tree !Tree

minN = 4

io s n t = printf "%s of depth %d\t check: %d\n" s n t

main = do
    n <- getArgs >>= readIO . head
    let maxN     = max (minN + 2) n
        stretchN = maxN + 1

    -- stretch memory tree
    let c = check (make 0 stretchN)
    io "stretch tree" stretchN c

    -- allocate a long lived tree
    let !long    = make 0 maxN

    -- allocate, walk, and deallocate many bottom-up binary trees
    let vs = (parMap rdeepseq) (depth' maxN) [minN,minN+2..maxN]
    mapM_ (\((m,d,i)) -> io (show m ++ "\t trees") d i) vs

    -- confirm the the long-lived binary tree still exists
    io "long lived tree" maxN (check long)

-- generate many trees
depth' :: Int -> Int -> (Int,Int,Int)
depth' m d =
  (2*n,d,sumT d n 0)
  where
    n = 1 `shiftL` (m - d + minN)

-- allocate and check lots of trees
sumT :: Int -> Int -> Int -> Int
sumT d i t = go i t 
  where
    go 0 t = t
    go i t = go (i-1) (t + a + b)

    a = check (make i    d)
    b = check (make (-i) d)

-- traverse the tree, counting up the nodes
check :: Tree -> Int
check Nil          = 0
check (Node i l r) = i + check l - check r

-- build a tree
make :: Int -> Int -> Tree
make i 0 = Node i Nil Nil
make i d = Node i (make (i2-1) d2) (make i2 d2)
  where i2 = 2*i
        d2 = d-1

Proposed entry

Unboxes the strict fields

{-# OPTIONS -fbang-patterns -funbox-strict-fields #-}
--
-- The Great Computer Language Shootout
-- http://shootout.alioth.debian.org/
--
-- Contributed by Don Stewart
--

import System
import Data.Bits
import Text.Printf

data Tree = Nil | Node !Int Tree Tree

minN = 4

io s !n !t = printf "%s of depth %d\t check: %d\n" s n t

main = do
    n <- getArgs >>= readIO . head
    let maxN     = max (minN + 2) n
        stretchN = maxN + 1

    -- stretch memory tree
    let c = check (make 0 stretchN)
    io "stretch tree" stretchN c

    -- allocate a long lived tree
    let long    = make 0 maxN

    -- allocate, walk, and deallocate many bottom-up binary trees
    let vs = depth minN maxN
    mapM_ (\((m,d,i)) -> io (show m ++ "\t trees") d i) vs

    -- confirm the the long-lived binary tree still exists
    io "long lived tree" maxN (check long)

-- generate many trees
depth :: Int -> Int -> [(Int,Int,Int)]
depth !d !m
    | d <= m    = (2*n,d,sumT d n 0) : depth (d+2) m
    | otherwise = []
  where !n = 1 `shiftL` (m - d + minN)

-- allocate and check lots of trees
sumT :: Int -> Int -> Int -> Int
sumT !d 0 t = t
sumT  d i t = sumT d (i-1) (t + a + b)
  where a = check (make i    d)
        b = check (make (-i) d)

-- traverse the tree, counting up the nodes
check :: Tree -> Int
check Nil          = 0
check (Node i l r) = i + check l - check r

-- build a tree
make :: Int -> Int -> Tree
make i 0 = Node i Nil Nil
make i d = Node i (make (i2-1) d2) (make i2 d2)
  where i2 = 2*i; d2 = d-1

Newly submitted to shootout

This is a trivial modification of Don Stewart's to add parallelism.

{-# OPTIONS -fbang-patterns -funbox-strict-fields #-}
--
-- The Computer Language Shootout
-- http://shootout.alioth.debian.org/
--
-- Contributed by Don Stewart
-- Modified by Stephen Blackheath to parallelize (a very tiny tweak)
--

import System
import Data.Bits
import Text.Printf
import Control.Parallel.Strategies

--
-- an artificially strict tree.
--
-- normally you would ensure the branches are lazy, but this benchmark
-- requires strict allocation.
--
data Tree = Nil | Node !Int !Tree !Tree

minN = 4

io s n t = printf "%s of depth %d\t check: %d\n" s n t

main = do
    n <- getArgs >>= readIO . head
    let maxN     = max (minN + 2) n
        stretchN = maxN + 1

    -- stretch memory tree
    let c = check (make 0 stretchN)
    io "stretch tree" stretchN c

    -- allocate a long lived tree
    let !long    = make 0 maxN

    -- allocate, walk, and deallocate many bottom-up binary trees
    let vs = parMap rnf id $ depth minN maxN
    mapM_ (\((m,d,i)) -> io (show m ++ "\t trees") d i) vs

    -- confirm the the long-lived binary tree still exists
    io "long lived tree" maxN (check long)

-- generate many trees
depth :: Int -> Int -> [(Int,Int,Int)]
depth d m
    | d <= m    = (2*n,d,sumT d n 0) : depth (d+2) m
    | otherwise = []
  where n = 1 `shiftL` (m - d + minN)

-- allocate and check lots of trees
sumT :: Int -> Int -> Int -> Int
sumT d 0 t = t
sumT  d i t = sumT d (i-1) (t + a + b)
  where a = check (make i    d)
        b = check (make (-i) d)

-- traverse the tree, counting up the nodes
check :: Tree -> Int
check Nil          = 0
check (Node i l r) = i + check l - check r

-- build a tree
make :: Int -> Int -> Tree
make i 0 = Node i Nil Nil
make i d = Node i (make (i2-1) d2) (make i2 d2)
  where i2 = 2*i; d2 = d-1

(Old) Current entry

Ported to ghc 6.6 Submitted

{-# OPTIONS -fbang-patterns #-}

--
-- The Great Computer Language Shootout
-- http://shootout.alioth.debian.org/
--
-- Simon Marlow
-- Rewritten by Don Stewart
--

import System
import Data.Bits
import Text.Printf

data Tree = Nil | Node !Int Tree Tree

minDepth = 4

io s n t = printf "%s of depth %d\t check: %d\n" s n t

main = do
    maxDepth <- getArgs >>= return . max (minDepth+2) . read . head :: IO Int

    let stretch = make 0 (maxDepth+1)
    io "stretch tree" (maxDepth+1) (check stretch)

    let long    = make 0 maxDepth

    let vs = depth minDepth maxDepth
    mapM_ (\(P m d i) -> io (show m ++ "\t trees") d i) vs

    io "long lived tree" maxDepth (check long)

data P = P !Int !Int !Int

depth :: Int -> Int -> [P]
depth !d !m
    | d > m     = []
    | otherwise = P (2*n) d (sumT n d 0) : depth (d+2) m
  where
    n = 1 `shiftL` (m - d + minDepth)

sumT :: Int -> Int -> Int -> Int
sumT !0 !d !t = t
sumT i d t    = sumT (i-1) d (t + a + b)
    where a = check (make i    d)
          b = check (make (-i) d)

make :: Int -> Int -> Tree
make !i !0 = Node i Nil Nil
make  i  d = Node i (make (i2-1) d2) (make i2 d2)
    where
        i2 = 2*i
        d2 = d-1

check :: Tree -> Int
check Nil          = 0
check (Node i l r) = i + check l - check r

Old entry

Shortest entry in any language, and almost twice as fast as old entry on my box.

Was speculatively disqualified.

{-# OPTIONS_GHC -fglasgow-exts -O2 -optc-O3 -funbox-strict-fields #-}
-- The Great Computer Language Shootout
-- http://shootout.alioth.debian.org/
-- Simon Marlow
-- Shortened by Don Stewart

import System; import Text.Printf; import Monad

data Tree = Nil | Node !Int Tree Tree

min' = 4 :: Int

main = do max' <- getArgs >>= return . max (min'+2) . read . head
          printf "stretch tree of depth %d\t check: %d\n" (max'+1) (itemCheck $ make 0 (max'+1))
          depthLoop min' max'
          printf "long lived tree of depth %d\t check: %d\n" max' (itemCheck $ make 0 max')

depthLoop d m = when (d <= m) $ do
    printf "%d\t trees of depth %d\t check: %d\n" (2*n) d (sumLoop n d 0)
    depthLoop (d+2) m 
    where n = 2^(m - d + min')

sumLoop 0 d acc = acc
sumLoop k d acc = c `seq` sumLoop (k-1) d (acc + c + c')
    where (c,c')  = (itemCheck (make k d), itemCheck (make (-1*k) d))

make i (0::Int) = i `seq` Nil
make i  d       = Node i (make ((2*i)-1) (d-1)) (make (2*i) (d-1))

itemCheck Nil = 0
itemCheck (Node x l r) = x + itemCheck l - itemCheck r

Old Entry

{-# OPTIONS -O3 -optc-O3 #-}
-- The Great Computer Language Shootout
-- http://shootout.alioth.debian.org/
-- contributed by Einar Karttunen

import System

data Tree = Node  Int Tree Tree | Nil

main = do [n] <- getArgs
          let max' = max (min'+2) (read n)
          showItemCheck (max'+1) (make 0 (max'+1)) "stretch tree of depth "
          let longlived = make 0 max'
          depthLoop min' max'
          showItemCheck max' longlived "long lived tree of depth "

min' :: Int
min' = 4

showItemCheck d a s = putStrLn (s++show d++"\t check: "++show (itemCheck a))

showCheck i d check = putStrLn (show (2*i)++"\t trees of depth "++show d++"\t check: "++show check)


depthLoop d m | d > m = return ()
depthLoop d m         = showCheck n d (sumLoop n d 0) >> depthLoop (d+2) m
              where n = 2^(m - d + min')



sumLoop :: Int -> Int -> Int -> Int
sumLoop 0 d acc = acc
sumLoop k d acc = c `seq` sumLoop (k-1) d (acc + c + c')
    where c  = itemCheck (make k d)
          c' = itemCheck (make (-1*k) d)

make :: Int -> Int -> Tree
make i 0 = Nil
make i d = Node i (make ((2*i)-1) (d-1)) (make (2*i) (d-1))

itemCheck Nil = 0
itemCheck (Node x l r) = x + itemCheck l - itemCheck r