mirror of
https://github.com/GreemDev/Ryujinx.git
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98c838b24c
Replaces BitUtils.CountTrailingZeros/CountLeadingZeros/IsPowerOfTwo with BitOperations methods
129 lines
3.3 KiB
C#
129 lines
3.3 KiB
C#
using Ryujinx.Common;
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using System.Numerics;
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namespace Ryujinx.HLE.HOS.Kernel.Common
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{
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class MersenneTwister
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{
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private int _index;
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private uint[] _mt;
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public MersenneTwister(uint seed)
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{
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_mt = new uint[624];
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_mt[0] = seed;
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for (int mtIdx = 1; mtIdx < _mt.Length; mtIdx++)
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{
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uint prev = _mt[mtIdx - 1];
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_mt[mtIdx] = (uint)(0x6c078965 * (prev ^ (prev >> 30)) + mtIdx);
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}
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_index = _mt.Length;
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}
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public long GenRandomNumber(long min, long max)
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{
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long range = max - min;
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if (min == max)
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{
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return min;
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}
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if (range == -1)
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{
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// Increment would cause a overflow, special case.
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return GenRandomNumber(2, 2, 32, 0xffffffffu, 0xffffffffu);
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}
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range++;
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// This is log2(Range) plus one.
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int nextRangeLog2 = 64 - BitOperations.LeadingZeroCount((ulong)range);
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// If Range is already power of 2, subtract one to use log2(Range) directly.
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int rangeLog2 = nextRangeLog2 - (BitOperations.IsPow2(range) ? 1 : 0);
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int parts = rangeLog2 > 32 ? 2 : 1;
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int bitsPerPart = rangeLog2 / parts;
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int fullParts = parts - (rangeLog2 - parts * bitsPerPart);
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uint mask = 0xffffffffu >> (32 - bitsPerPart);
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uint maskPlus1 = 0xffffffffu >> (31 - bitsPerPart);
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long randomNumber;
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do
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{
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randomNumber = GenRandomNumber(parts, fullParts, bitsPerPart, mask, maskPlus1);
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}
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while ((ulong)randomNumber >= (ulong)range);
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return min + randomNumber;
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}
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private long GenRandomNumber(
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int parts,
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int fullParts,
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int bitsPerPart,
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uint mask,
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uint maskPlus1)
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{
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long randomNumber = 0;
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int part = 0;
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for (; part < fullParts; part++)
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{
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randomNumber <<= bitsPerPart;
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randomNumber |= GenRandomNumber() & mask;
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}
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for (; part < parts; part++)
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{
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randomNumber <<= bitsPerPart + 1;
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randomNumber |= GenRandomNumber() & maskPlus1;
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}
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return randomNumber;
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}
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private uint GenRandomNumber()
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{
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if (_index >= _mt.Length)
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{
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Twist();
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}
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uint value = _mt[_index++];
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value ^= value >> 11;
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value ^= (value << 7) & 0x9d2c5680;
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value ^= (value << 15) & 0xefc60000;
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value ^= value >> 18;
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return value;
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}
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private void Twist()
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{
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for (int mtIdx = 0; mtIdx < _mt.Length; mtIdx++)
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{
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uint value = (_mt[mtIdx] & 0x80000000) + (_mt[(mtIdx + 1) % _mt.Length] & 0x7fffffff);
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_mt[mtIdx] = _mt[(mtIdx + 397) % _mt.Length] ^ (value >> 1);
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if ((value & 1) != 0)
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{
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_mt[mtIdx] ^= 0x9908b0df;
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}
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}
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_index = 0;
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}
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}
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}
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