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/zipf_distribution.h | 269 ++++++++++++++++++++++++++++++++++++++++ 1 file changed, 269 insertions(+) create mode 100644 absl/random/zipf_distribution.h (limited to 'absl/random/zipf_distribution.h') diff --git a/absl/random/zipf_distribution.h b/absl/random/zipf_distribution.h new file mode 100644 index 000000000000..1e4dba8b4e0c --- /dev/null +++ b/absl/random/zipf_distribution.h @@ -0,0 +1,269 @@ +// 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_ZIPF_DISTRIBUTION_H_ +#define ABSL_RANDOM_ZIPF_DISTRIBUTION_H_ + +#include +#include +#include +#include +#include +#include + +#include "absl/random/internal/iostream_state_saver.h" +#include "absl/random/uniform_real_distribution.h" + +namespace absl { + +// absl::zipf_distribution produces random integer-values in the range [0, k], +// distributed according to the discrete probability function: +// +// P(x) = (v + x) ^ -q +// +// The parameter `v` must be greater than 0 and the parameter `q` must be +// greater than 1. If either of these parameters take invalid values then the +// behavior is undefined. +// +// IntType is the result_type generated by the generator. It must be of integral +// type; a static_assert ensures this is the case. +// +// The implementation is based on W.Hormann, G.Derflinger: +// +// "Rejection-Inversion to Generate Variates from Monotone Discrete +// Distributions" +// +// http://eeyore.wu-wien.ac.at/papers/96-04-04.wh-der.ps.gz +// +template +class zipf_distribution { + public: + using result_type = IntType; + + class param_type { + public: + using distribution_type = zipf_distribution; + + // Preconditions: k > 0, v > 0, q > 1 + // The precondidtions are validated when NDEBUG is not defined via + // a pair of assert() directives. + // If NDEBUG is defined and either or both of these parameters take invalid + // values, the behavior of the class is undefined. + explicit param_type(result_type k = (std::numeric_limits::max)(), + double q = 2.0, double v = 1.0); + + result_type k() const { return k_; } + double q() const { return q_; } + double v() const { return v_; } + + friend bool operator==(const param_type& a, const param_type& b) { + return a.k_ == b.k_ && a.q_ == b.q_ && a.v_ == b.v_; + } + friend bool operator!=(const param_type& a, const param_type& b) { + return !(a == b); + } + + private: + friend class zipf_distribution; + inline double h(double x) const; + inline double hinv(double x) const; + inline double compute_s() const; + inline double pow_negative_q(double x) const; + + // Parameters here are exactly the same as the parameters of Algorithm ZRI + // in the paper. + IntType k_; + double q_; + double v_; + + double one_minus_q_; // 1-q + double s_; + double one_minus_q_inv_; // 1 / 1-q + double hxm_; // h(k + 0.5) + double hx0_minus_hxm_; // h(x0) - h(k + 0.5) + + static_assert(std::is_integral::value, + "Class-template absl::zipf_distribution<> must be " + "parameterized using an integral type."); + }; + + zipf_distribution() + : zipf_distribution((std::numeric_limits::max)()) {} + + explicit zipf_distribution(result_type k, double q = 2.0, double v = 1.0) + : param_(k, q, v) {} + + explicit zipf_distribution(const param_type& p) : param_(p) {} + + void reset() {} + + 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); + + result_type k() const { return param_.k(); } + double q() const { return param_.q(); } + double v() const { return param_.v(); } + + 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 k(); } + + friend bool operator==(const zipf_distribution& a, + const zipf_distribution& b) { + return a.param_ == b.param_; + } + friend bool operator!=(const zipf_distribution& a, + const zipf_distribution& b) { + return a.param_ != b.param_; + } + + private: + param_type param_; +}; + +// -------------------------------------------------------------------------- +// Implementation details follow +// -------------------------------------------------------------------------- + +template +zipf_distribution::param_type::param_type( + typename zipf_distribution::result_type k, double q, double v) + : k_(k), q_(q), v_(v), one_minus_q_(1 - q) { + assert(q > 1); + assert(v > 0); + assert(k > 0); + one_minus_q_inv_ = 1 / one_minus_q_; + + // Setup for the ZRI algorithm (pg 17 of the paper). + // Compute: h(i max) => h(k + 0.5) + constexpr double kMax = 18446744073709549568.0; + double kd = static_cast(k); + // TODO(absl-team): Determine if this check is needed, and if so, add a test + // that fails for k > kMax + if (kd > kMax) { + // Ensure that our maximum value is capped to a value which will + // round-trip back through double. + kd = kMax; + } + hxm_ = h(kd + 0.5); + + // Compute: h(0) + const bool use_precomputed = (v == 1.0 && q == 2.0); + const double h0x5 = use_precomputed ? (-1.0 / 1.5) // exp(-log(1.5)) + : h(0.5); + const double elogv_q = (v_ == 1.0) ? 1 : pow_negative_q(v_); + + // h(0) = h(0.5) - exp(log(v) * -q) + hx0_minus_hxm_ = (h0x5 - elogv_q) - hxm_; + + // And s + s_ = use_precomputed ? 0.46153846153846123 : compute_s(); +} + +template +double zipf_distribution::param_type::h(double x) const { + // std::exp(one_minus_q_ * std::log(v_ + x)) * one_minus_q_inv_; + x += v_; + return (one_minus_q_ == -1.0) + ? (-1.0 / x) // -exp(-log(x)) + : (std::exp(std::log(x) * one_minus_q_) * one_minus_q_inv_); +} + +template +double zipf_distribution::param_type::hinv(double x) const { + // std::exp(one_minus_q_inv_ * std::log(one_minus_q_ * x)) - v_; + return -v_ + ((one_minus_q_ == -1.0) + ? (-1.0 / x) // exp(-log(-x)) + : std::exp(one_minus_q_inv_ * std::log(one_minus_q_ * x))); +} + +template +double zipf_distribution::param_type::compute_s() const { + // 1 - hinv(h(1.5) - std::exp(std::log(v_ + 1) * -q_)); + return 1.0 - hinv(h(1.5) - pow_negative_q(v_ + 1.0)); +} + +template +double zipf_distribution::param_type::pow_negative_q(double x) const { + // std::exp(std::log(x) * -q_); + return q_ == 2.0 ? (1.0 / (x * x)) : std::exp(std::log(x) * -q_); +} + +template +template +typename zipf_distribution::result_type +zipf_distribution::operator()( + URBG& g, const param_type& p) { // NOLINT(runtime/references) + absl::uniform_real_distribution uniform_double; + double k; + for (;;) { + const double v = uniform_double(g); + const double u = p.hxm_ + v * p.hx0_minus_hxm_; + const double x = p.hinv(u); + k = rint(x); // std::floor(x + 0.5); + if (k > p.k()) continue; // reject k > max_k + if (k - x <= p.s_) break; + const double h = p.h(k + 0.5); + const double r = p.pow_negative_q(p.v_ + k); + if (u >= h - r) break; + } + IntType ki = static_cast(k); + assert(ki <= p.k_); + return ki; +} + +template +std::basic_ostream& operator<<( + std::basic_ostream& os, // NOLINT(runtime/references) + const zipf_distribution& x) { + using stream_type = + typename random_internal::stream_format_type::type; + auto saver = random_internal::make_ostream_state_saver(os); + os.precision(random_internal::stream_precision_helper::kPrecision); + os << static_cast(x.k()) << os.fill() << x.q() << os.fill() + << x.v(); + return os; +} + +template +std::basic_istream& operator>>( + std::basic_istream& is, // NOLINT(runtime/references) + zipf_distribution& x) { // NOLINT(runtime/references) + using result_type = typename zipf_distribution::result_type; + using param_type = typename zipf_distribution::param_type; + using stream_type = + typename random_internal::stream_format_type::type; + stream_type k; + double q; + double v; + + auto saver = random_internal::make_istream_state_saver(is); + is >> k >> q >> v; + if (!is.fail()) { + x.param(param_type(static_cast(k), q, v)); + } + return is; +} + +} // namespace absl. + +#endif // ABSL_RANDOM_ZIPF_DISTRIBUTION_H_ -- cgit 1.4.1