43 lines
1.2 KiB
C#
43 lines
1.2 KiB
C#
using System;
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namespace XWorld.Framework
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{
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// SplitMix64：跨平台确定性、无浮点、状态即种子（便于快照/复盘）
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public sealed class DeterministicRandom : IRandom
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{
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private ulong _state;
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public DeterministicRandom(ulong seed)
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{
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_state = seed;
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}
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// 当前内部状态；用它构造新实例可从"下一步"继续同一序列
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public ulong State => _state;
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private ulong NextU64()
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{
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_state += 0x9E3779B97F4A7C15UL;
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ulong z = _state;
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z = (z ^ (z >> 30)) * 0xBF58476D1CE4E5B9UL;
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z = (z ^ (z >> 27)) * 0x94D049BB133111EBUL;
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return z ^ (z >> 31);
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}
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public int Next(int maxExclusive)
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{
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if (maxExclusive <= 0)
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throw new ArgumentOutOfRangeException(nameof(maxExclusive), "maxExclusive 必须为正");
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ulong bound = (ulong)maxExclusive;
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// 拒绝采样，消除取模偏差
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ulong threshold = (ulong.MaxValue - bound + 1) % bound;
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while (true)
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{
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ulong r = NextU64();
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if (r >= threshold) return (int)(r % bound);
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}
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}
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}
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}
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