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Diffstat (limited to 'third_party/abseil_cpp/absl/random/exponential_distribution.h')
-rw-r--r-- | third_party/abseil_cpp/absl/random/exponential_distribution.h | 165 |
1 files changed, 0 insertions, 165 deletions
diff --git a/third_party/abseil_cpp/absl/random/exponential_distribution.h b/third_party/abseil_cpp/absl/random/exponential_distribution.h deleted file mode 100644 index b5caf8a1e1f3..000000000000 --- a/third_party/abseil_cpp/absl/random/exponential_distribution.h +++ /dev/null @@ -1,165 +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_EXPONENTIAL_DISTRIBUTION_H_ -#define ABSL_RANDOM_EXPONENTIAL_DISTRIBUTION_H_ - -#include <cassert> -#include <cmath> -#include <istream> -#include <limits> -#include <type_traits> - -#include "absl/meta/type_traits.h" -#include "absl/random/internal/fast_uniform_bits.h" -#include "absl/random/internal/generate_real.h" -#include "absl/random/internal/iostream_state_saver.h" - -namespace absl { -ABSL_NAMESPACE_BEGIN - -// absl::exponential_distribution: -// Generates a number conforming to an exponential distribution and is -// equivalent to the standard [rand.dist.pois.exp] distribution. -template <typename RealType = double> -class exponential_distribution { - public: - using result_type = RealType; - - class param_type { - public: - using distribution_type = exponential_distribution; - - explicit param_type(result_type lambda = 1) : lambda_(lambda) { - assert(lambda > 0); - neg_inv_lambda_ = -result_type(1) / lambda_; - } - - result_type lambda() const { return lambda_; } - - friend bool operator==(const param_type& a, const param_type& b) { - return a.lambda_ == b.lambda_; - } - - friend bool operator!=(const param_type& a, const param_type& b) { - return !(a == b); - } - - private: - friend class exponential_distribution; - - result_type lambda_; - result_type neg_inv_lambda_; - - static_assert( - std::is_floating_point<RealType>::value, - "Class-template absl::exponential_distribution<> must be parameterized " - "using a floating-point type."); - }; - - exponential_distribution() : exponential_distribution(1) {} - - explicit exponential_distribution(result_type lambda) : param_(lambda) {} - - explicit exponential_distribution(const param_type& p) : param_(p) {} - - 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); - - 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 std::numeric_limits<result_type>::infinity(); - } - - result_type lambda() const { return param_.lambda(); } - - friend bool operator==(const exponential_distribution& a, - const exponential_distribution& b) { - return a.param_ == b.param_; - } - friend bool operator!=(const exponential_distribution& a, - const exponential_distribution& b) { - return a.param_ != b.param_; - } - - private: - param_type param_; - random_internal::FastUniformBits<uint64_t> fast_u64_; -}; - -// -------------------------------------------------------------------------- -// Implementation details follow -// -------------------------------------------------------------------------- - -template <typename RealType> -template <typename URBG> -typename exponential_distribution<RealType>::result_type -exponential_distribution<RealType>::operator()( - URBG& g, // NOLINT(runtime/references) - const param_type& p) { - using random_internal::GenerateNegativeTag; - using random_internal::GenerateRealFromBits; - using real_type = - absl::conditional_t<std::is_same<RealType, float>::value, float, double>; - - const result_type u = GenerateRealFromBits<real_type, GenerateNegativeTag, - false>(fast_u64_(g)); // U(-1, 0) - - // log1p(-x) is mathematically equivalent to log(1 - x) but has more - // accuracy for x near zero. - return p.neg_inv_lambda_ * std::log1p(u); -} - -template <typename CharT, typename Traits, typename RealType> -std::basic_ostream<CharT, Traits>& operator<<( - std::basic_ostream<CharT, Traits>& os, // NOLINT(runtime/references) - const exponential_distribution<RealType>& x) { - auto saver = random_internal::make_ostream_state_saver(os); - os.precision(random_internal::stream_precision_helper<RealType>::kPrecision); - os << x.lambda(); - return os; -} - -template <typename CharT, typename Traits, typename RealType> -std::basic_istream<CharT, Traits>& operator>>( - std::basic_istream<CharT, Traits>& is, // NOLINT(runtime/references) - exponential_distribution<RealType>& x) { // NOLINT(runtime/references) - using result_type = typename exponential_distribution<RealType>::result_type; - using param_type = typename exponential_distribution<RealType>::param_type; - result_type lambda; - - auto saver = random_internal::make_istream_state_saver(is); - lambda = random_internal::read_floating_point<result_type>(is); - if (!is.fail()) { - x.param(param_type(lambda)); - } - return is; -} - -ABSL_NAMESPACE_END -} // namespace absl - -#endif // ABSL_RANDOM_EXPONENTIAL_DISTRIBUTION_H_ |