mirror of
https://github.com/love2d/love.git
synced 2026-08-14 01:20:56 +02:00
Alex Szpakowski
85 lines
2.4 KiB
C++
85 lines
2.4 KiB
C++
/**
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* Copyright (c) 2006-2013 LOVE Development Team
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*
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* This software is provided 'as-is', without any express or implied
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* warranty. In no event will the authors be held liable for any damages
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* arising from the use of this software.
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*
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* Permission is granted to anyone to use this software for any purpose,
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* including commercial applications, and to alter it and redistribute it
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* freely, subject to the following restrictions:
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*
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* 1. The origin of this software must not be misrepresented; you must not
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* claim that you wrote the original software. If you use this software
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* in a product, an acknowledgment in the product documentation would be
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* appreciated but is not required.
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* 2. Altered source versions must be plainly marked as such, and must not be
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* misrepresented as being the original software.
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* 3. This notice may not be removed or altered from any source distribution.
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**/
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#include "RandomGenerator.h"
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// STL
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#include <cmath>
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namespace love
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{
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namespace math
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{
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// 64 bit Xorshift implementation taken from the end of Sec. 3 (page 4) in
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// George Marsaglia, "Xorshift RNGs", Journal of Statistical Software, Vol.8 (Issue 14), 2003
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RandomGenerator::RandomGenerator()
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: last_randomnormal(std::numeric_limits<double>::infinity())
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{
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// because it is too big for some compilers to handle ... if you know what
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// i mean
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#ifdef LOVE_BIG_ENDIAN
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rng_state.b32.a = 0x0139408D;
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rng_state.b32.b = 0xCBBF7A44;
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#else
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rng_state.b32.b = 0x0139408D;
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rng_state.b32.a = 0xCBBF7A44;
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#endif
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}
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void RandomGenerator::setState(RandomGenerator::State state)
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{
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// 0 xor 0 is still 0, so Xorshift can't generate new numbers.
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if (state.b64 == 0)
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throw love::Exception("Invalid random state.");
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rng_state = state;
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}
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uint64 RandomGenerator::rand()
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{
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rng_state.b64 ^= (rng_state.b64 << 13);
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rng_state.b64 ^= (rng_state.b64 >> 7);
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rng_state.b64 ^= (rng_state.b64 << 17);
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return rng_state.b64;
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}
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// Box–Muller transform
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double RandomGenerator::randomNormal(double stddev)
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{
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// use cached number if possible
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if (last_randomnormal != std::numeric_limits<double>::infinity())
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{
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double r = last_randomnormal;
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last_randomnormal = std::numeric_limits<double>::infinity();
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return r * stddev;
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}
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double r = sqrt(-2.0 * log(1. - random()));
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double phi = 2.0 * LOVE_M_PI * (1. - random());
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last_randomnormal = r * cos(phi);
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return r * sin(phi) * stddev;
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}
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} // math
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} // love
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