d95794ec8a
As many open source projects have started doing it, we're removing the current year from the copyright notice, so that we don't need to bump it every year. It seems like only the first year of publication is technically relevant for copyright notices, and even that seems to be something that many companies stopped listing altogether (in a version controlled codebase, the commits are a much better source of date of publication than a hardcoded copyright statement). We also now list Godot Engine contributors first as we're collectively the current maintainers of the project, and we clarify that the "exclusive" copyright of the co-founders covers the timespan before opensourcing (their further contributions are included as part of Godot Engine contributors). Also fixed "cf." Frenchism - it's meant as "refer to / see".
140 lines
6.1 KiB
C++
140 lines
6.1 KiB
C++
/**************************************************************************/
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/* random_pcg.h */
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/**************************************************************************/
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/* This file is part of: */
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/* GODOT ENGINE */
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/* https://godotengine.org */
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/**************************************************************************/
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/* Copyright (c) 2014-present Godot Engine contributors (see AUTHORS.md). */
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/* Copyright (c) 2007-2014 Juan Linietsky, Ariel Manzur. */
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/* */
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/* Permission is hereby granted, free of charge, to any person obtaining */
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/* a copy of this software and associated documentation files (the */
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/* "Software"), to deal in the Software without restriction, including */
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/* without limitation the rights to use, copy, modify, merge, publish, */
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/* distribute, sublicense, and/or sell copies of the Software, and to */
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/* permit persons to whom the Software is furnished to do so, subject to */
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/* the following conditions: */
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/* */
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/* The above copyright notice and this permission notice shall be */
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/* included in all copies or substantial portions of the Software. */
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/* */
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/* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, */
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/* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF */
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/* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. */
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/* IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY */
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/* CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, */
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/* TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE */
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/* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. */
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/**************************************************************************/
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#ifndef RANDOM_PCG_H
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#define RANDOM_PCG_H
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#include "core/math/math_defs.h"
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#include "thirdparty/misc/pcg.h"
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#include <math.h>
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#if defined(__GNUC__)
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#define CLZ32(x) __builtin_clz(x)
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#elif defined(_MSC_VER)
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#include <intrin.h>
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static int __bsr_clz32(uint32_t x) {
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unsigned long index;
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_BitScanReverse(&index, x);
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return 31 - index;
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}
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#define CLZ32(x) __bsr_clz32(x)
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#else
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#endif
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#if defined(__GNUC__)
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#define LDEXP(s, e) __builtin_ldexp(s, e)
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#define LDEXPF(s, e) __builtin_ldexpf(s, e)
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#else
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#include <math.h>
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#define LDEXP(s, e) ldexp(s, e)
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#define LDEXPF(s, e) ldexp(s, e)
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#endif
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class RandomPCG {
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pcg32_random_t pcg;
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uint64_t current_seed = 0; // The seed the current generator state started from.
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uint64_t current_inc = 0;
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public:
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static const uint64_t DEFAULT_SEED = 12047754176567800795U;
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static const uint64_t DEFAULT_INC = PCG_DEFAULT_INC_64;
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RandomPCG(uint64_t p_seed = DEFAULT_SEED, uint64_t p_inc = DEFAULT_INC);
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_FORCE_INLINE_ void seed(uint64_t p_seed) {
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current_seed = p_seed;
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pcg32_srandom_r(&pcg, current_seed, current_inc);
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}
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_FORCE_INLINE_ uint64_t get_seed() { return current_seed; }
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_FORCE_INLINE_ void set_state(uint64_t p_state) { pcg.state = p_state; }
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_FORCE_INLINE_ uint64_t get_state() const { return pcg.state; }
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void randomize();
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_FORCE_INLINE_ uint32_t rand() {
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return pcg32_random_r(&pcg);
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}
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_FORCE_INLINE_ uint32_t rand(uint32_t bounds) {
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return pcg32_boundedrand_r(&pcg, bounds);
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}
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// Obtaining floating point numbers in [0, 1] range with "good enough" uniformity.
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// These functions sample the output of rand() as the fraction part of an infinite binary number,
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// with some tricks applied to reduce ops and branching:
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// 1. Instead of shifting to the first 1 and connecting random bits, we simply set the MSB and LSB to 1.
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// Provided that the RNG is actually uniform bit by bit, this should have the exact same effect.
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// 2. In order to compensate for exponent info loss, we count zeros from another random number,
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// and just add that to the initial offset.
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// This has the same probability as counting and shifting an actual bit stream: 2^-n for n zeroes.
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// For all numbers above 2^-96 (2^-64 for floats), the functions should be uniform.
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// However, all numbers below that threshold are floored to 0.
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// The thresholds are chosen to minimize rand() calls while keeping the numbers within a totally subjective quality standard.
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// If clz or ldexp isn't available, fall back to bit truncation for performance, sacrificing uniformity.
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_FORCE_INLINE_ double randd() {
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#if defined(CLZ32)
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uint32_t proto_exp_offset = rand();
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if (unlikely(proto_exp_offset == 0)) {
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return 0;
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}
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uint64_t significand = (((uint64_t)rand()) << 32) | rand() | 0x8000000000000001U;
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return LDEXP((double)significand, -64 - CLZ32(proto_exp_offset));
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#else
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#pragma message("RandomPCG::randd - intrinsic clz is not available, falling back to bit truncation")
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return (double)(((((uint64_t)rand()) << 32) | rand()) & 0x1FFFFFFFFFFFFFU) / (double)0x1FFFFFFFFFFFFFU;
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#endif
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}
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_FORCE_INLINE_ float randf() {
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#if defined(CLZ32)
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uint32_t proto_exp_offset = rand();
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if (unlikely(proto_exp_offset == 0)) {
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return 0;
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}
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return LDEXPF((float)(rand() | 0x80000001), -32 - CLZ32(proto_exp_offset));
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#else
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#pragma message("RandomPCG::randf - intrinsic clz is not available, falling back to bit truncation")
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return (float)(rand() & 0xFFFFFF) / (float)0xFFFFFF;
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#endif
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}
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_FORCE_INLINE_ double randfn(double p_mean, double p_deviation) {
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return p_mean + p_deviation * (cos(Math_TAU * randd()) * sqrt(-2.0 * log(randd()))); // Box-Muller transform
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}
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_FORCE_INLINE_ float randfn(float p_mean, float p_deviation) {
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return p_mean + p_deviation * (cos((float)Math_TAU * randf()) * sqrt(-2.0 * log(randf()))); // Box-Muller transform
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}
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double random(double p_from, double p_to);
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float random(float p_from, float p_to);
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int random(int p_from, int p_to);
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};
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#endif // RANDOM_PCG_H
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