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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,86 @@ | ||
| using System.Numerics; | ||
| using System.Runtime.CompilerServices; | ||
|
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| namespace Lynx; | ||
|
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| public class LynxRandom : Random | ||
| { | ||
| private readonly XoshiroImpl _impl; | ||
|
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| public LynxRandom() | ||
| { | ||
| _impl = new XoshiroImpl(this); | ||
| } | ||
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| public LynxRandom(int seed) : base(seed) | ||
| { | ||
| _impl = new XoshiroImpl(this); | ||
| } | ||
|
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| /// <summary> | ||
| /// Based on dotnet/runtime implementation, | ||
| /// https://github.com/dotnet/runtime/blob/508fef51e841aa16ffed1aae32bf4793a2cea363/src/libraries/System.Private.CoreLib/src/System/Random.Xoshiro256StarStarImpl.cs | ||
| /// </summary> | ||
| /// <returns></returns> | ||
| public ulong NextUInt64() => _impl.NextUInt64(); | ||
|
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| /// <summary> | ||
| /// Based on dotnet/runtime implementation, | ||
| /// https://github.com/dotnet/runtime/blob/a7f96cb070ffb8adf266b2e09d26759d7f978a60/src/libraries/System.Private.CoreLib/src/System/Random.Xoshiro256StarStarImpl.cs | ||
| /// <see cref="NextUInt64"/> is subsequently based on the algorithm from http://prng.di.unimi.it/xoshiro256starstar.c | ||
| /// Written in 2018 by David Blackman and Sebastiano Vigna ([email protected]) | ||
| /// To the extent possible under law, the author has dedicated all copyright | ||
| /// and related and neighboring rights to this software to the public domain | ||
| /// worldwide. This software is distributed without any warranty. | ||
| /// See <http://creativecommons.org/publicdomain/zero/1.0/>. | ||
| /// </summary> | ||
| internal sealed class XoshiroImpl | ||
| { | ||
| private ulong _s0, _s1, _s2, _s3; | ||
|
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| public XoshiroImpl(Random random) | ||
| { | ||
| do | ||
| { | ||
| _s0 = InternalNextUInt64(); | ||
| _s1 = InternalNextUInt64(); | ||
| _s2 = InternalNextUInt64(); | ||
| _s3 = InternalNextUInt64(); | ||
| } | ||
| while ((_s0 | _s1 | _s2 | _s3) == 0); // at least one value must be non-zero | ||
|
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| // 'Naive' version of what we're trying to achieve | ||
| ulong InternalNextUInt64() | ||
| { | ||
| Span<byte> arr = stackalloc byte[8]; | ||
| random.NextBytes(arr); | ||
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| return BitConverter.ToUInt64(arr); | ||
| } | ||
| } | ||
|
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| [MethodImpl(MethodImplOptions.AggressiveInlining)] | ||
| public ulong NextUInt64() | ||
| { | ||
| ulong s0 = _s0, s1 = _s1, s2 = _s2, s3 = _s3; | ||
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| ulong result = BitOperations.RotateLeft(s1 * 5, 7) * 9; | ||
| ulong t = s1 << 17; | ||
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| s2 ^= s0; | ||
| s3 ^= s1; | ||
| s1 ^= s2; | ||
| s0 ^= s3; | ||
|
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| s2 ^= t; | ||
| s3 = BitOperations.RotateLeft(s3, 45); | ||
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| _s0 = s0; | ||
| _s1 = s1; | ||
| _s2 = s2; | ||
| _s3 = s3; | ||
|
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| return result; | ||
| } | ||
| } | ||
| } |
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