Question

我使用GKARC4RandomSource（来自GameKit）生成随机数。设置种子后，我会生成一些随机数。在同一个实例上，但后者，我设置完全相同的种子，我再次生成一些数字。由于种子是相同的，我期待相同的数字，但这不会发生。我错过了什么？代码：

let randSource = GKARC4RandomSource()

    func foo() {
        print("1st sequence")
        randSource.seed = "seed".data(using: .utf8)!
        for _ in 0...10 {
            print(randSource.nextInt())
        }
    }


    func bar() {
        print("2nd sequence")
        randSource.seed = "seed".data(using: .utf8)!
        for _ in 0...10 {
            print(randSource.nextInt())
        }
    }

    foo()
    bar()

输出：第一序列 1077893367 -527596564 188760480 -1473410833 1247450388 155479986 -1227640578 -1952625186 -1819582711 1494875350 238061911 第二序列 -815382461 1319464721 -496336642 1307036859 -1543687700 1786062933 63740842 657867659 -1908618575 360960015 75414057

Answer 1

documentation for GKARC4RandomSource建议在初始化程序中使用seed。

使用相同种子数据初始化的任何两个随机源都将生成相同的随机数序列。要复制现有GKARC4Random Source实例的行为，请阅读实例的种子属性然后通过传递创建一个新实例结果数据到init（seed :)初始化器。

如果您使用init(seed:)，则有效：

func foo() {
    print("1st sequence")

    let seed = "seed".data(using: .utf8)!
    let randSource = GKARC4RandomSource(seed: seed)
    for _ in 0...10 {
        print(randSource.nextInt())
    }
}


func bar() {
    print("2nd sequence")

    let seed = "seed".data(using: .utf8)!
    let randSource = GKARC4RandomSource(seed: seed)
    for _ in 0...10 {
        print(randSource.nextInt())
    }
}

foo()
bar()

<强>输出

1st sequence
-907495547
-1853348607
-891423934
-1115481462
-1946427034
-1478051111
1807292425
525674909
-1209007346
-1508915292
-1396618639
2nd sequence
-907495547
-1853348607
-891423934
-1115481462
-1946427034
-1478051111
1807292425
525674909
-1209007346
-1508915292
-1396618639

设置GKARC4RandomSource的种子

1 个答案: