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Diffstat (limited to '')
| -rw-r--r-- | comphelper/source/misc/random.cxx | 121 |
1 files changed, 121 insertions, 0 deletions
diff --git a/comphelper/source/misc/random.cxx b/comphelper/source/misc/random.cxx new file mode 100644 index 000000000..260db3a54 --- /dev/null +++ b/comphelper/source/misc/random.cxx @@ -0,0 +1,121 @@ +/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */ +/* + * This file is part of the LibreOffice project. + * + * This Source Code Form is subject to the terms of the Mozilla Public + * License, v. 2.0. If a copy of the MPL was not distributed with this + * file, You can obtain one at http://mozilla.org/MPL/2.0/. + * + * Contributor(s): + * Copyright (C) 2012 Tino Kluge <tino.kluge@hrz.tu-chemnitz.de> + */ + +#include <comphelper/random.hxx> +#include <rtl/instance.hxx> +#include <sal/log.hxx> +#include <assert.h> +#include <time.h> +#include <mutex> +#include <random> +#include <stdexcept> +#if defined HAVE_VALGRIND_HEADERS +#include <valgrind/memcheck.h> +#endif + +// this is nothing but a simple wrapper around +// the std::random generators + +namespace comphelper::rng +{ + +// underlying random number generator +// std::mt19937 implements the Mersenne twister algorithm which +// is fast and has good statistical properties, it produces integers +// in the range of [0, 2^32-1] internally +// memory requirement: 625*sizeof(uint32_t) +// http://en.wikipedia.org/wiki/Mersenne_twister +#define STD_RNG_ALGO std::mt19937 + +namespace { + +struct RandomNumberGenerator +{ + std::mutex mutex; + STD_RNG_ALGO global_rng; + RandomNumberGenerator() + { + bool bRepeatable = (getenv("SAL_RAND_REPEATABLE") != nullptr); + // valgrind on some platforms (e.g.Ubuntu16.04) does not support the new Intel RDRAND instructions, + // which leads to "Illegal Opcode" errors, so just turn off randomness. +#if defined HAVE_VALGRIND_HEADERS + if (RUNNING_ON_VALGRIND) + bRepeatable = true; +#endif + if (bRepeatable) + { + global_rng.seed(42); + return; + } + + try + { + std::random_device rd; + // initialises the state of the global random number generator + // should only be called once. + // (note, a few std::variate_generator<> (like normal) have their + // own state which would need a reset as well to guarantee identical + // sequence of numbers, e.g. via myrand.distribution().reset()) + global_rng.seed(rd() ^ time(nullptr)); + } + catch (std::runtime_error& e) + { + SAL_WARN("comphelper", "Using std::random_device failed: " << e.what()); + global_rng.seed(time(nullptr)); + } + } +}; + +class theRandomNumberGenerator : public rtl::Static<RandomNumberGenerator, theRandomNumberGenerator> {}; + +} + +// uniform ints [a,b] distribution +int uniform_int_distribution(int a, int b) +{ + std::uniform_int_distribution<int> dist(a, b); + auto & gen = theRandomNumberGenerator::get(); + std::scoped_lock<std::mutex> g(gen.mutex); + return dist(gen.global_rng); +} + +// uniform ints [a,b] distribution +unsigned int uniform_uint_distribution(unsigned int a, unsigned int b) +{ + std::uniform_int_distribution<unsigned int> dist(a, b); + auto & gen = theRandomNumberGenerator::get(); + std::scoped_lock<std::mutex> g(gen.mutex); + return dist(gen.global_rng); +} + +// uniform size_t [a,b] distribution +size_t uniform_size_distribution(size_t a, size_t b) +{ + std::uniform_int_distribution<size_t> dist(a, b); + auto & gen = theRandomNumberGenerator::get(); + std::scoped_lock<std::mutex> g(gen.mutex); + return dist(gen.global_rng); +} + +// uniform size_t [a,b) distribution +double uniform_real_distribution(double a, double b) +{ + assert(a < b); + std::uniform_real_distribution<double> dist(a, b); + auto & gen = theRandomNumberGenerator::get(); + std::scoped_lock<std::mutex> g(gen.mutex); + return dist(gen.global_rng); +} + +} // namespace + +/* vim:set shiftwidth=4 softtabstop=4 expandtab: */ |