引用此代码:F# Static Member Type Constraints
为什么,例如,
let gL = G_of 1L
[1L..100000L] |> List.map (fun n -> factorize gL n)
显着慢于
[1L..100000L] |> List.map (fun n -> factorize (G_of 1L) n)
通过查看Reflector,我可以看到编译器正在以非常不同的方式处理每一个,但是有太多的东西让我破译本质的区别。天真地我认为前者会比后者表现更好,因为gL是预先计算的,而G_of 1L必须计算100,000次(至少看起来是这样)。
[修改
看起来这可能是F#2.0 / .NET 2.0 / Release-mode的错误,请参阅@ gradbot的回答和讨论。
答案 0 :(得分:1)
Reflector显示test2()变为4个类,而test1()变成了两个类。这只发生在调试模式下。 Reflector在发布模式下显示相同的代码(每个类一个)。不幸的是,当我尝试在C#中查看源代码时,Reflector崩溃了,而且IL很长。
let test1() =
let gL = G_of 1L
[1L..1000000L] |> List.map (fun n -> factorize gL n)
let test2() =
[1L..1000000L] |> List.map (fun n -> factorize (G_of 1L) n)
快速基准。
let sw = Stopwatch.StartNew()
test1() |> ignore
sw.Stop()
Console.WriteLine("test1 {0}ms", sw.ElapsedMilliseconds)
let sw2 = Stopwatch.StartNew()
test2() |> ignore
sw2.Stop()
Console.WriteLine("test2 {0}ms", sw2.ElapsedMilliseconds)
基准测试在I7 950 @ 3368Mhz,Windows 7 64位,VS2010 F#2.0上运行
x86调试
test1 8216ms
test2 8237ms
x86发布
test1 6654ms
test2 6680ms
x64调试
test1 10304ms
test2 10348ms
x64发布
test1 8858ms
test2 8977ms
这是完整的代码。
open System
open System.Diagnostics
let inline zero_of (target:'a) : 'a = LanguagePrimitives.GenericZero<'a>
let inline one_of (target:'a) : 'a = LanguagePrimitives.GenericOne<'a>
let inline two_of (target:'a) : 'a = one_of(target) + one_of(target)
let inline three_of (target:'a) : 'a = two_of(target) + one_of(target)
let inline negone_of (target:'a) : 'a = zero_of(target) - one_of(target)
let inline any_of (target:'a) (x:int) : 'a =
let one:'a = one_of target
let zero:'a = zero_of target
let xu = if x > 0 then 1 else -1
let gu:'a = if x > 0 then one else zero-one
let rec get i g =
if i = x then g
else get (i+xu) (g+gu)
get 0 zero
type G<'a> = {
negone:'a
zero:'a
one:'a
two:'a
three:'a
any: int -> 'a
}
let inline G_of (target:'a) : (G<'a>) = {
zero = zero_of target
one = one_of target
two = two_of target
three = three_of target
negone = negone_of target
any = any_of target
}
let inline factorizeG n =
let g = G_of n
let rec factorize n j flist =
if n = g.one then flist
elif n % j = g.zero then factorize (n/j) j (j::flist)
else factorize n (j + g.one) (flist)
factorize n g.two []
let inline factorize (g:G<'a>) n = //'
let rec factorize n j flist =
if n = g.one then flist
elif n % j = g.zero then factorize (n/j) j (j::flist)
else factorize n (j + g.one) (flist)
factorize n g.two []
let test1() =
let gL = G_of 1L
[1L..100000L] |> List.map (fun n -> factorize gL n)
let test2() =
[1L..100000L] |> List.map (fun n -> factorize (G_of 1L) n)
let sw2 = Stopwatch.StartNew()
test1() |> ignore
sw2.Stop()
Console.WriteLine("test1 {0}ms", sw2.ElapsedMilliseconds)
let sw = Stopwatch.StartNew()
test2() |> ignore
sw.Stop()
Console.WriteLine("test2 {0}ms", sw.ElapsedMilliseconds)
Console.ReadLine() |> ignore