F＃編譯器會引發OutOfMemoryException異常

Question

我使用的項目包含了大量的由單一的基類繼承的類。在單元測試中，我需要根據類型和數據比較收到的結果。

當我使用匹配在條件列表包含大約足夠多的不同條件的情況下通過類型進行比較編譯器拋出OutOfMemoryException。

例如，下面的F＃代碼編譯過程中引發的System.OutOfMemoryException（參數錯誤FS0193）（和編譯了約30秒的異常被拋出前）

type IBaseClass() = class end 

type IChildClass1() = inherit IBaseClass() 

type IChildClass2() = inherit IBaseClass() 

type IChildClass3() = inherit IBaseClass() 

type IChildClass4() = inherit IBaseClass() 

type IChildClass5() = inherit IBaseClass() 

type IChildClass6() = inherit IBaseClass() 

type IChildClass7() = inherit IBaseClass() 

type IChildClass8() = inherit IBaseClass() 

type IChildClass9() = inherit IBaseClass() 

type IChildClass10() = inherit IBaseClass() 

type IChildClass11() = inherit IBaseClass() 

type IChildClass12() = inherit IBaseClass() 

type IChildClass13() = inherit IBaseClass() 

type IChildClass14() = inherit IBaseClass() 

type IChildClass15() = inherit IBaseClass() 

type IChildClass16() = inherit IBaseClass() 

type IChildClass17() = inherit IBaseClass() 

type IChildClass18() = inherit IBaseClass() 

type IChildClass19() = inherit IBaseClass() 

type IChildClass20() = inherit IBaseClass() 


let AreEqual (original: IBaseClass) (compareWith: IBaseClass) : bool = 
    match (original, compareWith) with 
    | (:? IChildClass1 as a), (:? IChildClass1 as b) -> a = b 
    | (:? IChildClass2 as a), (:? IChildClass2 as b) -> a = b 
    | (:? IChildClass3 as a), (:? IChildClass3 as b) -> a = b 
    | (:? IChildClass4 as a), (:? IChildClass4 as b) -> a = b 
    | (:? IChildClass5 as a), (:? IChildClass5 as b) -> a = b 
    | (:? IChildClass6 as a), (:? IChildClass6 as b) -> a = b 
    | (:? IChildClass7 as a), (:? IChildClass7 as b) -> a = b 
    | (:? IChildClass8 as a), (:? IChildClass8 as b) -> a = b 
    | (:? IChildClass9 as a), (:? IChildClass9 as b) -> a = b 
    | (:? IChildClass10 as a), (:? IChildClass10 as b) -> a = b 
    | (:? IChildClass11 as a), (:? IChildClass11 as b) -> a = b 
    | (:? IChildClass12 as a), (:? IChildClass12 as b) -> a = b 
    | (:? IChildClass13 as a), (:? IChildClass13 as b) -> a = b 
    | (:? IChildClass14 as a), (:? IChildClass14 as b) -> a = b 
    | (:? IChildClass15 as a), (:? IChildClass15 as b) -> a = b 
    | (:? IChildClass16 as a), (:? IChildClass16 as b) -> a = b 
    | (:? IChildClass17 as a), (:? IChildClass17 as b) -> a = b 
    | (:? IChildClass18 as a), (:? IChildClass18 as b) -> a = b 
    | (:? IChildClass19 as a), (:? IChildClass19 as b) -> a = b 
    | (:? IChildClass20 as a), (:? IChildClass20 as b) -> a = b 
    | _ -> false 

我肯定可以添加IEquatable接口我IBaseClass類這將避免這種比賽建築的使用，或INT類成員（或枚舉）添加到 IBaseClass接口，使匹配不是類型，而是由一些int值。

注意，我試圖編譯在同一個項目中的MS VS 2010和MSVS 11測試版，並有相同的編譯器錯誤

問：爲什麼編譯器的OutOfMemoryException異常在我的情況發生（被它稱爲編譯錯誤或其他限制），我應該怎麼安排我比賽條件才能避免呢？

更新當我把課程變成歧視工會和使用類似比賽比較Fsc.exe編譯項目無一例外

type AllClasses = 
    | ChildClass1 of IChildClass1 | ChildClass2 of IChildClass2 | ChildClass3 of IChildClass3 | ChildClass4 of IChildClass4 | ChildClass5 of IChildClass5 | ChildClass6 of IChildClass6 
    | ChildClass7 of IChildClass7 | ChildClass8 of IChildClass8 | ChildClass9 of IChildClass9 | ChildClass10 of IChildClass10 | ChildClass11 of IChildClass11 | ChildClass12 of IChildClass12 
    | ChildClass13 of IChildClass13 | ChildClass14 of IChildClass14 | ChildClass15 of IChildClass15 | ChildClass16 of IChildClass16 | ChildClass17 of IChildClass17 | ChildClass18 of IChildClass18 
    | ChildClass19 of IChildClass19 | ChildClass20 of IChildClass20 

let AreEqual2 (original: AllClasses) (compareWith: AllClasses) : bool = 
    match (original, compareWith) with 
    | ChildClass1(a), ChildClass1(b) -> a = b 
    | ChildClass2(a), ChildClass2(b) -> a = b 
    | ChildClass3(a), ChildClass3(b) -> a = b 
    | ChildClass4(a), ChildClass4(b) -> a = b 
    | ChildClass5(a), ChildClass5(b) -> a = b 
    | ChildClass6(a), ChildClass6(b) -> a = b 
    | ChildClass7(a), ChildClass7(b) -> a = b 
    | ChildClass8(a), ChildClass8(b) -> a = b 
    | ChildClass9(a), ChildClass9(b) -> a = b 
    | ChildClass10(a), ChildClass10(b) -> a = b 
    | ChildClass11(a), ChildClass11(b) -> a = b 
    | ChildClass12(a), ChildClass12(b) -> a = b 
    | ChildClass13(a), ChildClass13(b) -> a = b 
    | ChildClass14(a), ChildClass14(b) -> a = b 
    | ChildClass15(a), ChildClass15(b) -> a = b 
    | ChildClass16(a), ChildClass16(b) -> a = b 
    | ChildClass17(a), ChildClass17(b) -> a = b 
    | ChildClass18(a), ChildClass18(b) -> a = b 
    | ChildClass19(a), ChildClass19(b) -> a = b 
    | ChildClass20(a), ChildClass20(b) -> a = b 
    | _ -> false 

感謝

Answer 1

這是通過怎樣的F＃編譯器引起的在這種情況下編譯元組的模式匹配。我不能完全確定什麼時候你在這個特定的問題和運行時編譯器將使用另一種方法，但在這裏就是爲什麼在這種情況下，失敗的解釋...

如果你寫一個模式匹配像在您的例子中，編譯器實際上決策樹，它可測試original（:? IChildClass1）的第一圖案，然後生成兩個分支。第一個分支檢查是否compareWith也IChildClass1。如果是的話，它會運行第一個案例。模式匹配的其餘部分則在這兩個分支的重複，所以你喜歡的東西（你可以在編譯的代碼尋找較小的數字使用ILSpy箱子檢查）：

if (original is IChildClass1) 
    if (compareWith is IChildClass1) 
    case #1 
    if (original is IChildClass2) 
    if (compareWith is IChildClass2) 
     case #2 
    if (original is IChildClass3) 
     (...) 
else 
    if (original is IChildClass2) 
    if (compareWith is IChildClass2) 
     case #2 
    if (original is IChildClass3) 
     (...) 

這意味着生成的代碼的大小與此模式匹配中的個案數成指數成比例。對於20種情況，編譯器會嘗試創建2^20個分支，這（意外）會失敗。