From e9324d926a9189e222741fce6e676f0944661a72 Mon Sep 17 00:00:00 2001 From: Abseil Team Date: Fri, 21 Jun 2019 13:11:42 -0700 Subject: Export of internal Abseil changes. -- 7a6ff16a85beb730c172d5d25cf1b5e1be885c56 by Laramie Leavitt : Internal change. PiperOrigin-RevId: 254454546 -- ff8f9bafaefc26d451f576ea4a06d150aed63f6f by Andy Soffer : Internal changes PiperOrigin-RevId: 254451562 -- deefc5b651b479ce36f0b4ef203e119c0c8936f2 by CJ Johnson : Account for subtracting unsigned values from the size of InlinedVector PiperOrigin-RevId: 254450625 -- 3c677316a27bcadc17e41957c809ca472d5fef14 by Andy Soffer : Add C++17's std::make_from_tuple to absl/utility/utility.h PiperOrigin-RevId: 254411573 -- 4ee3536a918830eeec402a28fc31a62c7c90b940 by CJ Johnson : Adds benchmark for the rest of the InlinedVector public API PiperOrigin-RevId: 254408378 -- e5a21a00700ee83498ff1efbf649169756463ee4 by CJ Johnson : Updates the definition of InlinedVector::shrink_to_fit() to be exception safe and adds exception safety tests for it. PiperOrigin-RevId: 254401387 -- 2ea82e72b86d82d78b4e4712a63a55981b53c64b by Laramie Leavitt : Use absl::InsecureBitGen in place of std::mt19937 in tests absl/random/...distribution_test.cc PiperOrigin-RevId: 254289444 -- fa099e02c413a7ffda732415e8105cad26a90337 by Andy Soffer : Internal changes PiperOrigin-RevId: 254286334 -- ce34b7f36933b30cfa35b9c9a5697a792b5666e4 by Andy Soffer : Internal changes PiperOrigin-RevId: 254273059 -- 6f9c473da7c2090c2e85a37c5f00622e8a912a89 by Jorg Brown : Change absl::container_internal::CompressedTuple to instantiate its internal Storage class with the name of the type it's holding, rather than the name of the Tuple. This is not an externally-visible change, other than less compiler memory is used and less debug information is generated. PiperOrigin-RevId: 254269285 -- 8bd3c186bf2fc0c55d8a2dd6f28a5327502c9fba by Andy Soffer : Adding short-hand IntervalClosed for IntervalClosedClosed and IntervalOpen for IntervalOpenOpen. PiperOrigin-RevId: 254252419 -- ea957f99b6a04fccd42aa05605605f3b44b1ecfd by Abseil Team : Do not directly use __SIZEOF_INT128__. In order to avoid linker errors when building with clang-cl (__fixunsdfti, __udivti3 and __fixunssfti are undefined), this CL uses ABSL_HAVE_INTRINSIC_INT128 which is not defined for clang-cl. PiperOrigin-RevId: 254250739 -- 89ab385cd26b34d64130bce856253aaba96d2345 by Andy Soffer : Internal changes PiperOrigin-RevId: 254242321 -- cffc793d93eca6d6bdf7de733847b6ab4a255ae9 by CJ Johnson : Adds benchmark for InlinedVector::reserve(size_type) PiperOrigin-RevId: 254199226 -- c90c7a9fa3c8f0c9d5114036979548b055ea2f2a by Gennadiy Rozental : Import of CCTZ from GitHub. PiperOrigin-RevId: 254072387 -- c4c388beae016c9570ab54ffa1d52660e4a85b7b by Laramie Leavitt : Internal cleanup. PiperOrigin-RevId: 254062381 -- d3c992e221cc74e5372d0c8fa410170b6a43c062 by Tom Manshreck : Update distributions.h to Abseil standards PiperOrigin-RevId: 254054946 -- d15ad0035c34ef11b14fadc5a4a2d3ec415f5518 by CJ Johnson : Removes functions with only one caller from the implementation details of InlinedVector by manually inlining the definitions PiperOrigin-RevId: 254005427 -- 2f37e807efc3a8ef1f4b539bdd379917d4151520 by Andy Soffer : Initial release of Abseil Random PiperOrigin-RevId: 253999861 -- 24ed1694b6430791d781ed533a8f8ccf6cac5856 by CJ Johnson : Updates the definition of InlinedVector::assign(...)/InlinedVector::operator=(...) to new, exception-safe implementations with exception safety tests to boot PiperOrigin-RevId: 253993691 -- 5613d95f5a7e34a535cfaeadce801441e990843e by CJ Johnson : Adds benchmarks for InlinedVector::shrink_to_fit() PiperOrigin-RevId: 253989647 -- 2a96ddfdac40bbb8cb6a7f1aeab90917067c6e63 by Abseil Team : Initial release of Abseil Random PiperOrigin-RevId: 253927497 -- bf1aff8fc9ffa921ad74643e9525ecf25b0d8dc1 by Andy Soffer : Initial release of Abseil Random PiperOrigin-RevId: 253920512 -- bfc03f4a3dcda3cf3a4b84bdb84cda24e3394f41 by Laramie Leavitt : Internal change. PiperOrigin-RevId: 253886486 -- 05036cfcc078ca7c5f581a00dfb0daed568cbb69 by Eric Fiselier : Don't include `winsock2.h` because it drags in `windows.h` and friends, and they define awful macros like OPAQUE, ERROR, and more. This has the potential to break abseil users. Instead we only forward declare `timeval` and require Windows users include `winsock2.h` themselves. This is both inconsistent and poor QoI, but so including 'windows.h' is bad too. PiperOrigin-RevId: 253852615 GitOrigin-RevId: 7a6ff16a85beb730c172d5d25cf1b5e1be885c56 Change-Id: Icd6aff87da26f29ec8915da856f051129987cef6 --- absl/random/discrete_distribution.h | 245 ++++++++++++++++++++++++++++++++++++ 1 file changed, 245 insertions(+) create mode 100644 absl/random/discrete_distribution.h (limited to 'absl/random/discrete_distribution.h') diff --git a/absl/random/discrete_distribution.h b/absl/random/discrete_distribution.h new file mode 100644 index 000000000000..1560f03c5fdd --- /dev/null +++ b/absl/random/discrete_distribution.h @@ -0,0 +1,245 @@ +// 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 +#include +#include +#include +#include +#include +#include +#include + +#include "absl/random/bernoulli_distribution.h" +#include "absl/random/internal/iostream_state_saver.h" +#include "absl/random/uniform_int_distribution.h" + +namespace absl { + +// 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 +class discrete_distribution { + public: + using result_type = IntType; + + class param_type { + public: + using distribution_type = discrete_distribution; + + param_type() { init(); } + + template + explicit param_type(InputIterator begin, InputIterator end) + : p_(begin, end) { + init(); + } + + explicit param_type(std::initializer_list weights) : p_(weights) { + init(); + } + + template + explicit param_type(size_t nw, double xmin, double xmax, + UnaryOperation fw) { + if (nw > 0) { + p_.reserve(nw); + double delta = (xmax - xmin) / static_cast(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& 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 p_; // normalized probabilities + std::vector> q_; // (acceptance, alternate) pairs + + static_assert(std::is_integral::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 + explicit discrete_distribution(InputIterator begin, InputIterator end) + : param_(begin, end) {} + + explicit discrete_distribution(std::initializer_list weights) + : param_(weights) {} + + template + explicit discrete_distribution(size_t nw, double xmin, double xmax, + UnaryOperation fw) + : param_(nw, xmin, xmax, std::move(fw)) {} + + void reset() {} + + // generating functions + template + result_type operator()(URBG& g) { // NOLINT(runtime/references) + return (*this)(g, param_); + } + + template + 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(param_.n()); + } // inclusive + + // NOTE [rand.dist.sample.discrete] returns a std::vector not a + // const std::vector&. + const std::vector& 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> InitDiscreteDistribution( + std::vector* probabilities); + +} // namespace random_internal + +template +void discrete_distribution::param_type::init() { + if (p_.empty()) { + p_.push_back(1.0); + q_.emplace_back(1.0, 0); + } else { + assert(n() <= (std::numeric_limits::max)()); + q_ = random_internal::InitDiscreteDistribution(&p_); + } +} + +template +template +typename discrete_distribution::result_type +discrete_distribution::operator()( + URBG& g, // NOLINT(runtime/references) + const param_type& p) { + const auto idx = absl::uniform_int_distribution(0, p.n())(g); + const auto& q = p.q_[idx]; + const bool selected = absl::bernoulli_distribution(q.first)(g); + return selected ? idx : static_cast(q.second); +} + +template +std::basic_ostream& operator<<( + std::basic_ostream& os, // NOLINT(runtime/references) + const discrete_distribution& 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::kPrecision); + for (const auto& p : probabilities) { + os << os.fill() << p; + } + return os; +} + +template +std::basic_istream& operator>>( + std::basic_istream& is, // NOLINT(runtime/references) + discrete_distribution& x) { // NOLINT(runtime/references) + using param_type = typename discrete_distribution::param_type; + auto saver = random_internal::make_istream_state_saver(is); + + size_t n; + std::vector 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(is); + if (is.fail()) return is; + p.push_back(tmp); + } + } + x.param(param_type(p.begin(), p.end())); + return is; +} + +} // namespace absl + +#endif // ABSL_RANDOM_DISCRETE_DISTRIBUTION_H_ -- cgit 1.4.1