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/log_uniform_int_distribution.h | 250 +++++++++++++++++++++++++++++ 1 file changed, 250 insertions(+) create mode 100644 absl/random/log_uniform_int_distribution.h (limited to 'absl/random/log_uniform_int_distribution.h') diff --git a/absl/random/log_uniform_int_distribution.h b/absl/random/log_uniform_int_distribution.h new file mode 100644 index 0000000..ac43416 --- /dev/null +++ b/absl/random/log_uniform_int_distribution.h @@ -0,0 +1,250 @@ +// 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_LOG_UNIFORM_INT_DISTRIBUTION_H_ +#define ABSL_RANDOM_LOG_UNIFORM_INT_DISTRIBUTION_H_ + +#include +#include +#include +#include +#include +#include +#include + +#include "absl/random/internal/distribution_impl.h" +#include "absl/random/internal/fastmath.h" +#include "absl/random/internal/iostream_state_saver.h" +#include "absl/random/internal/traits.h" +#include "absl/random/uniform_int_distribution.h" + +namespace absl { + +// log_uniform_int_distribution: +// +// Returns a random variate R in range [min, max] such that +// floor(log(R-min, base)) is uniformly distributed. +// We ensure uniformity by discretization using the +// boundary sets [0, 1, base, base * base, ... min(base*n, max)] +// +template +class log_uniform_int_distribution { + private: + using unsigned_type = + typename random_internal::make_unsigned_bits::type; + + public: + using result_type = IntType; + + class param_type { + public: + using distribution_type = log_uniform_int_distribution; + + explicit param_type( + result_type min = 0, + result_type max = (std::numeric_limits::max)(), + result_type base = 2) + : min_(min), + max_(max), + base_(base), + range_(static_cast(max_) - + static_cast(min_)), + log_range_(0) { + assert(max_ >= min_); + assert(base_ > 1); + + if (base_ == 2) { + // Determine where the first set bit is on range(), giving a log2(range) + // value which can be used to construct bounds. + log_range_ = (std::min)(random_internal::LeadingSetBit(range()), + std::numeric_limits::digits); + } else { + // NOTE: Computing the logN(x) introduces error from 2 sources: + // 1. Conversion of int to double loses precision for values >= + // 2^53, which may cause some log() computations to operate on + // different values. + // 2. The error introduced by the division will cause the result + // to differ from the expected value. + // + // Thus a result which should equal K may equal K +/- epsilon, + // which can eliminate some values depending on where the bounds fall. + const double inv_log_base = 1.0 / std::log(base_); + const double log_range = std::log(static_cast(range()) + 0.5); + log_range_ = static_cast(std::ceil(inv_log_base * log_range)); + } + } + + result_type(min)() const { return min_; } + result_type(max)() const { return max_; } + result_type base() const { return base_; } + + friend bool operator==(const param_type& a, const param_type& b) { + return a.min_ == b.min_ && a.max_ == b.max_ && a.base_ == b.base_; + } + + friend bool operator!=(const param_type& a, const param_type& b) { + return !(a == b); + } + + private: + friend class log_uniform_int_distribution; + + int log_range() const { return log_range_; } + unsigned_type range() const { return range_; } + + result_type min_; + result_type max_; + result_type base_; + unsigned_type range_; // max - min + int log_range_; // ceil(logN(range_)) + + static_assert(std::is_integral::value, + "Class-template absl::log_uniform_int_distribution<> must be " + "parameterized using an integral type."); + }; + + log_uniform_int_distribution() : log_uniform_int_distribution(0) {} + + explicit log_uniform_int_distribution( + result_type min, + result_type max = (std::numeric_limits::max)(), + result_type base = 2) + : param_(min, max, base) {} + + explicit log_uniform_int_distribution(const param_type& p) : param_(p) {} + + 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) { + return (p.min)() + Generate(g, p); + } + + result_type(min)() const { return (param_.min)(); } + result_type(max)() const { return (param_.max)(); } + result_type base() const { return param_.base(); } + + param_type param() const { return param_; } + void param(const param_type& p) { param_ = p; } + + friend bool operator==(const log_uniform_int_distribution& a, + const log_uniform_int_distribution& b) { + return a.param_ == b.param_; + } + friend bool operator!=(const log_uniform_int_distribution& a, + const log_uniform_int_distribution& b) { + return a.param_ != b.param_; + } + + private: + // Returns a log-uniform variate in the range [0, p.range()]. The caller + // should add min() to shift the result to the correct range. + template + unsigned_type Generate(URNG& g, // NOLINT(runtime/references) + const param_type& p); + + param_type param_; +}; + +template +template +typename log_uniform_int_distribution::unsigned_type +log_uniform_int_distribution::Generate( + URBG& g, // NOLINT(runtime/references) + const param_type& p) { + // sample e over [0, log_range]. Map the results of e to this: + // 0 => 0 + // 1 => [1, b-1] + // 2 => [b, (b^2)-1] + // n => [b^(n-1)..(b^n)-1] + const int e = absl::uniform_int_distribution(0, p.log_range())(g); + if (e == 0) { + return 0; + } + const int d = e - 1; + + unsigned_type base_e, top_e; + if (p.base() == 2) { + base_e = static_cast(1) << d; + + top_e = (e >= std::numeric_limits::digits) + ? (std::numeric_limits::max)() + : (static_cast(1) << e) - 1; + } else { + const double r = std::pow(p.base(), d); + const double s = (r * p.base()) - 1.0; + + base_e = (r > (std::numeric_limits::max)()) + ? (std::numeric_limits::max)() + : static_cast(r); + + top_e = (s > (std::numeric_limits::max)()) + ? (std::numeric_limits::max)() + : static_cast(s); + } + + const unsigned_type lo = (base_e >= p.range()) ? p.range() : base_e; + const unsigned_type hi = (top_e >= p.range()) ? p.range() : top_e; + + // choose uniformly over [lo, hi] + return absl::uniform_int_distribution(lo, hi)(g); +} + +template +std::basic_ostream& operator<<( + std::basic_ostream& os, // NOLINT(runtime/references) + const log_uniform_int_distribution& x) { + using stream_type = + typename random_internal::stream_format_type::type; + auto saver = random_internal::make_ostream_state_saver(os); + os << static_cast((x.min)()) << os.fill() + << static_cast((x.max)()) << os.fill() + << static_cast(x.base()); + return os; +} + +template +std::basic_istream& operator>>( + std::basic_istream& is, // NOLINT(runtime/references) + log_uniform_int_distribution& x) { // NOLINT(runtime/references) + using param_type = typename log_uniform_int_distribution::param_type; + using result_type = + typename log_uniform_int_distribution::result_type; + using stream_type = + typename random_internal::stream_format_type::type; + + stream_type min; + stream_type max; + stream_type base; + + auto saver = random_internal::make_istream_state_saver(is); + is >> min >> max >> base; + if (!is.fail()) { + x.param(param_type(static_cast(min), + static_cast(max), + static_cast(base))); + } + return is; +} + +} // namespace absl + +#endif // ABSL_RANDOM_LOG_UNIFORM_INT_DISTRIBUTION_H_ -- cgit v1.2.3