137 lines
4.0 KiB
C#
137 lines
4.0 KiB
C#
using System;
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namespace Barotrauma
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{
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/// <summary>
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/// Mersenne Twister based random
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/// </summary>
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public sealed class MTRandom : Random
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{
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private const int N = 624;
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private const int M = 397;
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private const uint MATRIX_A = 0x9908b0dfU;
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private const uint UPPER_MASK = 0x80000000U;
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private const uint LOWER_MASK = 0x7fffffffU;
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private const uint TEMPER1 = 0x9d2c5680U;
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private const uint TEMPER2 = 0xefc60000U;
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private const int TEMPER3 = 11;
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private const int TEMPER4 = 7;
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private const int TEMPER5 = 15;
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private const int TEMPER6 = 18;
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private UInt32[] mt;
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private int mti;
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private UInt32[] mag01;
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private const double c_realUnitInt = 1.0 / ((double)int.MaxValue + 1.0);
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/// <summary>
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/// Constructor with randomized seed
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/// </summary>
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public MTRandom()
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{
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Initialize((uint)Environment.TickCount);
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}
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/// <summary>
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/// Constructor with provided 32 bit seed
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/// </summary>
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[CLSCompliant(false)]
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public MTRandom(int seed)
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{
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Initialize((uint)Math.Abs(seed));
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}
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/// <summary>
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/// (Re)initialize this instance with provided 32 bit seed
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/// </summary>
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[CLSCompliant(false)]
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private void Initialize(uint seed)
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{
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mt = new UInt32[N];
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mti = N + 1;
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mag01 = new UInt32[] { 0x0U, MATRIX_A };
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mt[0] = seed;
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for (int i = 1; i < N; i++)
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mt[i] = (UInt32)(1812433253 * (mt[i - 1] ^ (mt[i - 1] >> 30)) + i);
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}
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/// <summary>
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/// Generates a random value from UInt32.MinValue to UInt32.MaxValue, inclusively
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/// </summary>
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[CLSCompliant(false)]
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private uint NextUInt32()
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{
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UInt32 y;
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if (mti >= N)
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{
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GenRandAll();
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mti = 0;
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}
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y = mt[mti++];
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y ^= (y >> TEMPER3);
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y ^= (y << TEMPER4) & TEMPER1;
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y ^= (y << TEMPER5) & TEMPER2;
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y ^= (y >> TEMPER6);
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return y;
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}
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/// <summary>
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/// Generates a random value that is greater or equal than 0 and less than Int32.MaxValue
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/// </summary>
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public override int Next()
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{
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var retval = (int)(0x7FFFFFFF & NextUInt32());
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if (retval == 0x7FFFFFFF)
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return NextInt32();
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return retval;
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}
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/// <summary>
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/// Returns a random value is greater or equal than 0 and less than maxValue
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/// </summary>
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public override int Next(int maxValue)
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{
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return (int)(NextDouble() * maxValue);
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}
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/// <summary>
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/// Generates a random value greater or equal than 0 and less or equal than Int32.MaxValue (inclusively)
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/// </summary>
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public int NextInt32()
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{
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return (int)(0x7FFFFFFF & NextUInt32());
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}
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/// <summary>
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/// Returns random value larger or equal to 0.0 and less than 1.0
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/// </summary>
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public override double NextDouble()
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{
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return c_realUnitInt * NextInt32();
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}
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private void GenRandAll()
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{
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int kk = 1;
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UInt32 y;
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UInt32 p;
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y = mt[0] & UPPER_MASK;
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do
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{
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p = mt[kk];
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mt[kk - 1] = mt[kk + (M - 1)] ^ ((y | (p & LOWER_MASK)) >> 1) ^ mag01[p & 1];
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y = p & UPPER_MASK;
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} while (++kk < N - M + 1);
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do
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{
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p = mt[kk];
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mt[kk - 1] = mt[kk + (M - N - 1)] ^ ((y | (p & LOWER_MASK)) >> 1) ^ mag01[p & 1];
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y = p & UPPER_MASK;
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} while (++kk < N);
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p = mt[0];
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mt[N - 1] = mt[M - 1] ^ ((y | (p & LOWER_MASK)) >> 1) ^ mag01[p & 1];
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}
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}
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}
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