31 lines
1.0 KiB
Swift
31 lines
1.0 KiB
Swift
// Copyright © 2024 Apple Inc.
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import Foundation
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// From https://github.com/apple/swift/blob/cb0fb1ea051631219c0b944b84c78571448d58c2/benchmark/utils/TestsUtils.swift#L254
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//
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// This is just a seedable RandomNumberGenerator for shuffle()
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// This is a fixed-increment version of Java 8's SplittableRandom generator.
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// It is a very fast generator passing BigCrush, with 64 bits of state.
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// See http://dx.doi.org/10.1145/2714064.2660195 and
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// http://docs.oracle.com/javase/8/docs/api/java/util/SplittableRandom.html
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//
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// Derived from public domain C implementation by Sebastiano Vigna
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// See http://xoshiro.di.unimi.it/splitmix64.c
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public struct SplitMix64: RandomNumberGenerator {
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private var state: UInt64
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public init(seed: UInt64) {
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self.state = seed
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}
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public mutating func next() -> UInt64 {
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self.state &+= 0x9e37_79b9_7f4a_7c15
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var z: UInt64 = self.state
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z = (z ^ (z &>> 30)) &* 0xbf58_476d_1ce4_e5b9
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z = (z ^ (z &>> 27)) &* 0x94d0_49bb_1331_11eb
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return z ^ (z &>> 31)
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}
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}
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