86 lines
1.7 KiB
C#
86 lines
1.7 KiB
C#
#region Copyright & License Information
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/*
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* Copyright 2007-2015 The OpenRA Developers (see AUTHORS)
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* This file is part of OpenRA, which is free software. It is made
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* available to you under the terms of the GNU General Public License
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* as published by the Free Software Foundation. For more information,
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* see COPYING.
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*/
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#endregion
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using System;
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namespace OpenRA.Support
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{
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// Quick & dirty Mersenne Twister [MT19937] implementation
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public class MersenneTwister
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{
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readonly uint[] mt = new uint[624];
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int index = 0;
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public int Last;
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public int TotalCount = 0;
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public MersenneTwister() : this(Environment.TickCount) { }
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public MersenneTwister(int seed)
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{
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mt[0] = (uint)seed;
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for (var i = 1u; i < mt.Length; i++)
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mt[i] = 1812433253u * (mt[i - 1] ^ (mt[i - 1] >> 30)) + i;
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}
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public int Next()
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{
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if (index == 0) Generate();
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var y = mt[index];
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y ^= y >> 11;
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y ^= (y << 7) & 2636928640;
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y ^= (y << 15) & 4022730752;
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y ^= y >> 18;
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index = (index + 1) % 624;
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TotalCount++;
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Last = (int)(y % int.MaxValue);
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return Last;
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}
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public int Next(int low, int high)
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{
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if (high < low)
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throw new ArgumentOutOfRangeException("high", "Maximum value is less than the minimum value.");
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var diff = high - low;
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if (diff <= 1)
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return low;
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return low + Next() % diff;
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}
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public int Next(int high)
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{
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return Next(0, high);
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}
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public float NextFloat()
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{
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return Math.Abs(Next() / (float)0x7fffffff);
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}
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void Generate()
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{
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unchecked
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{
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for (var i = 0u; i < mt.Length; i++)
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{
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var y = (mt[i] & 0x80000000) | (mt[(i + 1) % 624] & 0x7fffffff);
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mt[i] = mt[(i + 397u) % 624u] ^ (y >> 1);
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if ((y & 1) == 1)
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mt[i] = mt[i] ^ 2567483615;
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}
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}
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}
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}
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}
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