F＃编译器会引发OutOfMemoryException异常

Question

我使用的项目包含了大量的由单一的基类继承的类。在单元测试中，我需要根据类型和数据比较收到的结果。

当我使用匹配在条件列表包含大约足够多的不同条件的情况下通过类型进行比较编译器抛出OutOfMemoryException。

例如，下面的F＃代码编译过程中引发的System.OutOfMemoryException（参数错误FS0193）（和编译了约30秒的异常被抛出前）

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类这将避免这种比赛建筑的使用，或INT类成员（或枚举）添加到 IBaseClass接口，使匹配不是类型，而是由一些int值。

注意，我试图编译在同一个项目中的MS VS 2010和MSVS 11测试版，并有相同的编译器错误

问：为什么编译器的OutOfMemoryException异常在我的情况发生（被它称为编译错误或其他限制），我应该怎么安排我比赛条件才能避免呢？

更新当我把课程变成歧视工会和使用类似比赛比较Fsc.exe编译项目无一例外

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 

感谢

Answer 1

这是通过怎样的F＃编译器引起的在这种情况下编译元组的模式匹配。我不能完全确定什么时候你在这个特定的问题和运行时编译器将使用另一种方法，但在这里就是为什么在这种情况下，失败的解释...

如果你写一个模式匹配像在您的例子中，编译器实际上决策树，它可测试original（:? IChildClass1）的第一图案，然后生成两个分支。第一个分支检查是否compareWith也IChildClass1。如果是的话，它会运行第一个案例。模式匹配的其余部分则在这两个分支的重复，所以你喜欢的东西（你可以在编译的代码寻找较小的数字使用ILSpy箱子检查）：

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) 
     (...) 

这意味着生成的代码的大小与此模式匹配中的个案数成指数成比例。对于20种情况，编译器会尝试创建2^20个分支，这（意外）会失败。