some jhc weirdness

21 Mar 2009

      Hi,

after having adapted "binaries-tree" from
http://shootout.alioth.debian.org/u32q/benchmark.php?test=binarytrees&lang=ghc&box=1
to remove the dependency on Text.Printf (program below), I get the
following results.

1. reference run.

$ghc --make -O2 -fglasgow-exts -fasm prog.hs -o prog.ghc
$./prog.ghc 1
"stretch tree" of depth 7 check: -1
"128 trees" of depth 4 check: -128
"32 trees" of depth 6 check: -32
"long lived tree" of depth 6 check: -1

2. jhc run.

$jhc -o prog
 of depth 77 check: -1
 of depth 44 check: -128
 of depth 66 check: -32
 of depth 66 check: -1

$ ./prog.jhc 18
 of depth 1919 check: -1
segmentation fault

Maybe is it time to set up a bug tracker :)
Sylvain

--snip--
import System
import Data.Bits

--
-- 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 = putStrLn (show s++" of depth "++(show n)++" check: "++(show
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 ++ " 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
--snip--

sylvain

John Meacham

Taral

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