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F# CTP 2.0.0.0 vs. VS 2010 F# 2.0 Interactive build 4.0.30319.1
f#

Sorry for my pure English.
This code execute with F# CTP 2.0.0.0 Interacitve takes about 5 sec.
with VS 2010 F# 2.0 Interactive build 4.0.30319.1 takes about 25 sec.
Any idea ?

open System

let levenshteinDistance s1 s2 =
let sa,sb:char [] * char [] = Array.ofSeq s1, Array.ofSeq s2
let n = Array.length sa
let transform (narr:int []) c =
let zip3wrapper xs =
let m = (min n (Array.length xs))-1
Array.zip3 sa.[..m] narr.[..m] xs.[..m]
let compute z (c', x, y) =
List.min [y+1; z+1; x + abs (compare c' c)]
Array.scan compute (narr.[0]+1) (zip3wrapper narr.[1..])
let res = Array.fold transform [|0..n|] sb
res.[res.Length-1]

let aa = String.Concat( Array.create 1000 "abcde" )
let bb = String.Concat( Array.create 1000 "cdefg" )

let sw = new System.Diagnostics.Stopwatch()
sw.Start()
let res = levenshteinDistance aa bb
sw.Stop()
printfn "Time Duration : %A" sw.ElapsedMilliseconds
printfn "Result : %A" res

.

Interesting; I reproduce these results. Same for compiled; compiled for .NET 4, the program takes 5x as long as the one compiled for .NET 2. I'll have fsbugs look into it.

By on 11/16/2010 11:36 AM ()

I think I've found the reason of error. List.min - function.
I changed the code. Net 4 program take same time as Net 2.

let levenshteinDistance s1 s2 =
let sa,sb:char [] * char [] = Array.ofSeq s1, Array.ofSeq s2
let n = Array.length sa
let transform (narr:int []) c =
let zip3wrapper xs =
let m = (min n (Array.length xs))-1
Array.zip3 sa.[..m] narr.[..m] xs.[..m]
let compute z (c', x, y) =
min (y+1) (z+1)|> min (x + abs (compare c' c))
// List.min [y+1; z+1; x + abs (compare c' c)]
Array.scan compute (narr.[0]+1) (zip3wrapper narr.[1..])
let res = Array.fold transform [|0..n|] sb
res.[res.Length-1]

By on 11/17/2010 2:04 AM ()

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