142 lines
4.0 KiB
C
142 lines
4.0 KiB
C
/*
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* Brickworks
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*
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* Copyright (C) 2022, 2023 Orastron Srl unipersonale
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*
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* Brickworks is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, version 3 of the License.
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*
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* Brickworks is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with Brickworks. If not, see <http://www.gnu.org/licenses/>.
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*
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* File author: Stefano D'Angelo
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*/
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/*!
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* module_type {{{ utility }}}
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* version {{{ 1.0.0 }}}
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* requires {{{ bw_common }}}
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* description {{{
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* Pseudo-random number generators.
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*
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* These are good enough for music DSP applications but should not be
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* considered crypthographically secure.
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*
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* All functions in this module are [reentrant](api#reentrant-function),
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* [RT-safe](api#rt-safe-function), [thread-safe](api#thread-safe-function),
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* and have [no side effects](api#no-side-effects).
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*
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* The algorithms are based on the ["simplified" Permuted Congruential
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* Generator (PCG)](https://nullprogram.com/blog/2017/09/21/#permuted-congruential-generator-pcg)
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* by Chris Wellons, which is itself taken from
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*
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* M. E. O'Neill, "PCG: A Family of Simple Fast Space-Efficient Statistically
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* Good Algorithms for Random Number Generation", September 2014, available
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* at https://www.cs.hmc.edu/tr/hmc-cs-2014-0905.pdf.
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* }}}
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* changelog {{{
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* <ul>
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* <li>Version <strong>1.0.0</strong>:
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* <ul>
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* <li>Added one more assertion in <code>bw_randf()</code>.</li>
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* <li>Removed usage of reserved identifiers.</li>
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* </ul>
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* </li>
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* <li>Version <strong>0.6.0</strong>:
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* <ul>
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* <li>Added debugging code.</li>
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* <li>Removed dependency on bw_config.</li>
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* <li>Fixed harmless warning in <code>bw_randu32()</code>.</li>
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* </ul>
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* </li>
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* <li>Version <strong>0.2.0</strong>:
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* <ul>
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* <li>Refactored API.</li>
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* </ul>
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* </li>
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* <li>Version <strong>0.1.0</strong>:
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* <ul>
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* <li>First release.</li>
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* </ul>
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* </li>
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* </ul>
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* }}}
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*/
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#ifndef BW_RAND_H
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#define BW_RAND_H
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#include <bw_common.h>
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#ifdef __cplusplus
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extern "C" {
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#endif
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/*** Public API ***/
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/*! api {{{
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* #### bw_randu32()
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* ```>>> */
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static inline uint32_t bw_randu32(
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uint64_t * BW_RESTRICT state);
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/*! <<<```
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* Returns a pseudo-random unsigned 32-bit integer in the range
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* [`0`, `UINT32_MAX`].
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*
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* `state` is a pointer to a 64-bit unsigned integer storing the state
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* between calls and which gets updated by this function.
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*
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* #### bw_randf()
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* ```>>> */
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static inline float bw_randf(
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uint64_t * BW_RESTRICT state);
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/*! <<<```
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* Returns a pseudo-random unsigned 32-bit floating point number in the range
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* [`-1.f`, `1.f`].
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*
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* `state` is a pointer to a 64-bit unsigned integer storing the state
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* between calls and which gets updated by this function.
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* }}} */
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#ifdef __cplusplus
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}
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#endif
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/*** Implementation ***/
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#ifdef __cplusplus
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extern "C" {
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#endif
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/* WARNING: This part of the file is not part of the public API. Its content may
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* change at any time in future versions. Please, do not use it directly. */
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static inline uint32_t bw_randu32(
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uint64_t * BW_RESTRICT state) {
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BW_ASSERT(state != NULL);
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// Permuted Congruential Generator,
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// taken from https://nullprogram.com/blog/2017/09/21/
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*state = *state * 0x9b60933458e17d7d + 0xd737232eeccdf7ed;
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return (uint32_t)(*state >> (29 - (*state >> 61)));
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}
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static inline float bw_randf(
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uint64_t * BW_RESTRICT state) {
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BW_ASSERT(state != NULL);
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const float y = (2.f / (float)UINT32_MAX) * (float)bw_randu32(state) - 1.f;
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BW_ASSERT(bw_is_finite(y));
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return y;
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}
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#ifdef __cplusplus
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}
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#endif
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#endif
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