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Diffstat (limited to 'third_party/abseil_cpp/absl/random/discrete_distribution.h')
-rw-r--r-- | third_party/abseil_cpp/absl/random/discrete_distribution.h | 247 |
1 files changed, 0 insertions, 247 deletions
diff --git a/third_party/abseil_cpp/absl/random/discrete_distribution.h b/third_party/abseil_cpp/absl/random/discrete_distribution.h deleted file mode 100644 index 171aa11a1eb4..000000000000 --- a/third_party/abseil_cpp/absl/random/discrete_distribution.h +++ /dev/null @@ -1,247 +0,0 @@ -// Copyright 2017 The Abseil Authors. -// -// Licensed under the Apache License, Version 2.0 (the "License"); -// you may not use this file except in compliance with the License. -// You may obtain a copy of the License at -// -// https://www.apache.org/licenses/LICENSE-2.0 -// -// Unless required by applicable law or agreed to in writing, software -// distributed under the License is distributed on an "AS IS" BASIS, -// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. -// See the License for the specific language governing permissions and -// limitations under the License. - -#ifndef ABSL_RANDOM_DISCRETE_DISTRIBUTION_H_ -#define ABSL_RANDOM_DISCRETE_DISTRIBUTION_H_ - -#include <cassert> -#include <cmath> -#include <istream> -#include <limits> -#include <numeric> -#include <type_traits> -#include <utility> -#include <vector> - -#include "absl/random/bernoulli_distribution.h" -#include "absl/random/internal/iostream_state_saver.h" -#include "absl/random/uniform_int_distribution.h" - -namespace absl { -ABSL_NAMESPACE_BEGIN - -// absl::discrete_distribution -// -// A discrete distribution produces random integers i, where 0 <= i < n -// distributed according to the discrete probability function: -// -// P(i|p0,...,pn−1)=pi -// -// This class is an implementation of discrete_distribution (see -// [rand.dist.samp.discrete]). -// -// The algorithm used is Walker's Aliasing algorithm, described in Knuth, Vol 2. -// absl::discrete_distribution takes O(N) time to precompute the probabilities -// (where N is the number of possible outcomes in the distribution) at -// construction, and then takes O(1) time for each variate generation. Many -// other implementations also take O(N) time to construct an ordered sequence of -// partial sums, plus O(log N) time per variate to binary search. -// -template <typename IntType = int> -class discrete_distribution { - public: - using result_type = IntType; - - class param_type { - public: - using distribution_type = discrete_distribution; - - param_type() { init(); } - - template <typename InputIterator> - explicit param_type(InputIterator begin, InputIterator end) - : p_(begin, end) { - init(); - } - - explicit param_type(std::initializer_list<double> weights) : p_(weights) { - init(); - } - - template <class UnaryOperation> - explicit param_type(size_t nw, double xmin, double xmax, - UnaryOperation fw) { - if (nw > 0) { - p_.reserve(nw); - double delta = (xmax - xmin) / static_cast<double>(nw); - assert(delta > 0); - double t = delta * 0.5; - for (size_t i = 0; i < nw; ++i) { - p_.push_back(fw(xmin + i * delta + t)); - } - } - init(); - } - - const std::vector<double>& probabilities() const { return p_; } - size_t n() const { return p_.size() - 1; } - - friend bool operator==(const param_type& a, const param_type& b) { - return a.probabilities() == b.probabilities(); - } - - friend bool operator!=(const param_type& a, const param_type& b) { - return !(a == b); - } - - private: - friend class discrete_distribution; - - void init(); - - std::vector<double> p_; // normalized probabilities - std::vector<std::pair<double, size_t>> q_; // (acceptance, alternate) pairs - - static_assert(std::is_integral<result_type>::value, - "Class-template absl::discrete_distribution<> must be " - "parameterized using an integral type."); - }; - - discrete_distribution() : param_() {} - - explicit discrete_distribution(const param_type& p) : param_(p) {} - - template <typename InputIterator> - explicit discrete_distribution(InputIterator begin, InputIterator end) - : param_(begin, end) {} - - explicit discrete_distribution(std::initializer_list<double> weights) - : param_(weights) {} - - template <class UnaryOperation> - explicit discrete_distribution(size_t nw, double xmin, double xmax, - UnaryOperation fw) - : param_(nw, xmin, xmax, std::move(fw)) {} - - void reset() {} - - // generating functions - template <typename URBG> - result_type operator()(URBG& g) { // NOLINT(runtime/references) - return (*this)(g, param_); - } - - template <typename URBG> - result_type operator()(URBG& g, // NOLINT(runtime/references) - const param_type& p); - - const param_type& param() const { return param_; } - void param(const param_type& p) { param_ = p; } - - result_type(min)() const { return 0; } - result_type(max)() const { - return static_cast<result_type>(param_.n()); - } // inclusive - - // NOTE [rand.dist.sample.discrete] returns a std::vector<double> not a - // const std::vector<double>&. - const std::vector<double>& probabilities() const { - return param_.probabilities(); - } - - friend bool operator==(const discrete_distribution& a, - const discrete_distribution& b) { - return a.param_ == b.param_; - } - friend bool operator!=(const discrete_distribution& a, - const discrete_distribution& b) { - return a.param_ != b.param_; - } - - private: - param_type param_; -}; - -// -------------------------------------------------------------------------- -// Implementation details only below -// -------------------------------------------------------------------------- - -namespace random_internal { - -// Using the vector `*probabilities`, whose values are the weights or -// probabilities of an element being selected, constructs the proportional -// probabilities used by the discrete distribution. `*probabilities` will be -// scaled, if necessary, so that its entries sum to a value sufficiently close -// to 1.0. -std::vector<std::pair<double, size_t>> InitDiscreteDistribution( - std::vector<double>* probabilities); - -} // namespace random_internal - -template <typename IntType> -void discrete_distribution<IntType>::param_type::init() { - if (p_.empty()) { - p_.push_back(1.0); - q_.emplace_back(1.0, 0); - } else { - assert(n() <= (std::numeric_limits<IntType>::max)()); - q_ = random_internal::InitDiscreteDistribution(&p_); - } -} - -template <typename IntType> -template <typename URBG> -typename discrete_distribution<IntType>::result_type -discrete_distribution<IntType>::operator()( - URBG& g, // NOLINT(runtime/references) - const param_type& p) { - const auto idx = absl::uniform_int_distribution<result_type>(0, p.n())(g); - const auto& q = p.q_[idx]; - const bool selected = absl::bernoulli_distribution(q.first)(g); - return selected ? idx : static_cast<result_type>(q.second); -} - -template <typename CharT, typename Traits, typename IntType> -std::basic_ostream<CharT, Traits>& operator<<( - std::basic_ostream<CharT, Traits>& os, // NOLINT(runtime/references) - const discrete_distribution<IntType>& x) { - auto saver = random_internal::make_ostream_state_saver(os); - const auto& probabilities = x.param().probabilities(); - os << probabilities.size(); - - os.precision(random_internal::stream_precision_helper<double>::kPrecision); - for (const auto& p : probabilities) { - os << os.fill() << p; - } - return os; -} - -template <typename CharT, typename Traits, typename IntType> -std::basic_istream<CharT, Traits>& operator>>( - std::basic_istream<CharT, Traits>& is, // NOLINT(runtime/references) - discrete_distribution<IntType>& x) { // NOLINT(runtime/references) - using param_type = typename discrete_distribution<IntType>::param_type; - auto saver = random_internal::make_istream_state_saver(is); - - size_t n; - std::vector<double> p; - - is >> n; - if (is.fail()) return is; - if (n > 0) { - p.reserve(n); - for (IntType i = 0; i < n && !is.fail(); ++i) { - auto tmp = random_internal::read_floating_point<double>(is); - if (is.fail()) return is; - p.push_back(tmp); - } - } - x.param(param_type(p.begin(), p.end())); - return is; -} - -ABSL_NAMESPACE_END -} // namespace absl - -#endif // ABSL_RANDOM_DISCRETE_DISTRIBUTION_H_ |