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Mersenne Twister pseudorandom number generator.

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morkt 2015-11-02 05:40:57 +04:00
parent 91110ad1df
commit 456971553a
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ArcFormats/MersenneTwister.cs Normal file
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//! \file MersenneTwister.cs
//! \date Mon Nov 02 01:57:11 2015
//! \brief Mersenne Twister pseudorandom number generator.
//
// Copyright (C) 1997 Makoto Matsumoto and Takuji Nishimura.
//
// C# port by morkt
//
namespace GameRes.Utility
{
public class MersenneTwister
{
const uint DefaultSeed = 4357;
const int StateLength = 624;
const int StateM = 397;
const uint MatrixA = 0x9908B0DF;
const uint SignMask = 0x80000000;
const uint LowerMask = 0x7FFFFFFF;
const uint TemperingMaskB = 0x9D2C5680;
const uint TemperingMaskC = 0xEFC60000;
uint[] mt = new uint[StateLength];
int mti = StateLength;
public MersenneTwister (uint seed)
{
SRand (seed);
}
public void SRand (uint seed)
{
for (mti = 0; mti < mt.Length; ++mti)
{
uint upper = seed & 0xffff0000;
seed = 69069 * seed + 1;
mt[mti] = upper | (seed & 0xffff0000) >> 16;
seed = 69069 * seed + 1;
}
}
uint[] mag01 = { 0, MatrixA };
public uint Rand ()
{
uint y;
if (mti >= StateLength)
{
int kk;
for (kk = 0; kk < StateLength - StateM; kk++)
{
y = (mt[kk] & SignMask) | (mt[kk+1] & LowerMask);
mt[kk] = mt[kk + StateM] ^ (y >> 1) ^ mag01[y & 1];
}
for (; kk < StateLength-1; kk++)
{
y = (mt[kk] & SignMask) | (mt[kk+1] & LowerMask);
mt[kk] = mt[kk + StateM - StateLength] ^ (y >> 1) ^ mag01[y & 1];
}
y = (mt[StateLength-1] & SignMask) | (mt[0] & LowerMask);
mt[StateLength-1] = mt[StateM-1] ^ (y >> 1) ^ mag01[y & 1];
mti = 0;
}
y = mt[mti++];
y ^= y >> 11;
y ^= (y << 7) & TemperingMaskB;
y ^= (y << 15) & TemperingMaskC;
y ^= y >> 18;
return y;
}
}
}