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/internal/pcg_engine.h | 305 ++++++++++++++++++++++++++++++++++++++ 1 file changed, 305 insertions(+) create mode 100644 absl/random/internal/pcg_engine.h (limited to 'absl/random/internal/pcg_engine.h') diff --git a/absl/random/internal/pcg_engine.h b/absl/random/internal/pcg_engine.h new file mode 100644 index 000000000000..33fea0b9689f --- /dev/null +++ b/absl/random/internal/pcg_engine.h @@ -0,0 +1,305 @@ +// Copyright 2018 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_PCG_ENGINE_H_ +#define ABSL_RANDOM_PCG_ENGINE_H_ + +#include + +#include "absl/base/config.h" +#include "absl/meta/type_traits.h" +#include "absl/numeric/int128.h" +#include "absl/random/internal/fastmath.h" +#include "absl/random/internal/iostream_state_saver.h" + +namespace absl { +namespace random_internal { + +// pcg_engine is a simplified implementation of Melissa O'Neil's PCG engine in +// C++. PCG combines a linear congruential generator (LCG) with output state +// mixing functions to generate each random variate. pcg_engine supports only a +// single sequence (oneseq), and does not support streams. +// +// pcg_engine is parameterized by two types: +// Params, which provides the multiplier and increment values; +// Mix, which mixes the state into the result. +// +template +class pcg_engine { + static_assert(std::is_same::value, + "Class-template absl::pcg_engine must be parameterized by " + "Params and Mix with identical state_type"); + + static_assert(std::is_unsigned::value, + "Class-template absl::pcg_engine must be parameterized by " + "an unsigned Mix::result_type"); + + using params_type = Params; + using mix_type = Mix; + using state_type = typename Mix::state_type; + + public: + // C++11 URBG interface: + using result_type = typename Mix::result_type; + + static constexpr result_type(min)() { + return (std::numeric_limits::min)(); + } + + static constexpr result_type(max)() { + return (std::numeric_limits::max)(); + } + + explicit pcg_engine(uint64_t seed_value = 0) { seed(seed_value); } + + template ::value>> + explicit pcg_engine(SeedSequence&& seq) { + seed(seq); + } + + pcg_engine(const pcg_engine&) = default; + pcg_engine& operator=(const pcg_engine&) = default; + pcg_engine(pcg_engine&&) = default; + pcg_engine& operator=(pcg_engine&&) = default; + + result_type operator()() { + // Advance the LCG state, always using the new value to generate the output. + state_ = lcg(state_); + return Mix{}(state_); + } + + void seed(uint64_t seed_value = 0) { + state_type tmp = seed_value; + state_ = lcg(tmp + Params::increment()); + } + + template + typename absl::enable_if_t< + !std::is_convertible::value, void> + seed(SeedSequence&& seq) { + reseed(seq); + } + + void discard(uint64_t count) { state_ = advance(state_, count); } + + bool operator==(const pcg_engine& other) const { + return state_ == other.state_; + } + + bool operator!=(const pcg_engine& other) const { return !(*this == other); } + + template + friend typename absl::enable_if_t<(sizeof(state_type) == 16), + std::basic_ostream&> + operator<<( + std::basic_ostream& os, // NOLINT(runtime/references) + const pcg_engine& engine) { + auto saver = random_internal::make_ostream_state_saver(os); + random_internal::stream_u128_helper helper; + helper.write(pcg_engine::params_type::multiplier(), os); + os << os.fill(); + helper.write(pcg_engine::params_type::increment(), os); + os << os.fill(); + helper.write(engine.state_, os); + return os; + } + + template + friend typename absl::enable_if_t<(sizeof(state_type) <= 8), + std::basic_ostream&> + operator<<( + std::basic_ostream& os, // NOLINT(runtime/references) + const pcg_engine& engine) { + auto saver = random_internal::make_ostream_state_saver(os); + os << pcg_engine::params_type::multiplier() << os.fill(); + os << pcg_engine::params_type::increment() << os.fill(); + os << engine.state_; + return os; + } + + template + friend typename absl::enable_if_t<(sizeof(state_type) == 16), + std::basic_istream&> + operator>>( + std::basic_istream& is, // NOLINT(runtime/references) + pcg_engine& engine) { // NOLINT(runtime/references) + random_internal::stream_u128_helper helper; + auto mult = helper.read(is); + auto inc = helper.read(is); + auto tmp = helper.read(is); + if (mult != pcg_engine::params_type::multiplier() || + inc != pcg_engine::params_type::increment()) { + // signal failure by setting the failbit. + is.setstate(is.rdstate() | std::ios_base::failbit); + } + if (!is.fail()) { + engine.state_ = tmp; + } + return is; + } + + template + friend typename absl::enable_if_t<(sizeof(state_type) <= 8), + std::basic_istream&> + operator>>( + std::basic_istream& is, // NOLINT(runtime/references) + pcg_engine& engine) { // NOLINT(runtime/references) + state_type mult{}, inc{}, tmp{}; + is >> mult >> inc >> tmp; + if (mult != pcg_engine::params_type::multiplier() || + inc != pcg_engine::params_type::increment()) { + // signal failure by setting the failbit. + is.setstate(is.rdstate() | std::ios_base::failbit); + } + if (!is.fail()) { + engine.state_ = tmp; + } + return is; + } + + private: + state_type state_; + + // Returns the linear-congruential generator next state. + static inline constexpr state_type lcg(state_type s) { + return s * Params::multiplier() + Params::increment(); + } + + // Returns the linear-congruential arbitrary seek state. + inline state_type advance(state_type s, uint64_t n) const { + state_type mult = Params::multiplier(); + state_type inc = Params::increment(); + state_type m = 1; + state_type i = 0; + while (n > 0) { + if (n & 1) { + m *= mult; + i = i * mult + inc; + } + inc = (mult + 1) * inc; + mult *= mult; + n >>= 1; + } + return m * s + i; + } + + template + void reseed(SeedSequence& seq) { + using sequence_result_type = typename SeedSequence::result_type; + constexpr size_t kBufferSize = + sizeof(state_type) / sizeof(sequence_result_type); + sequence_result_type buffer[kBufferSize]; + seq.generate(std::begin(buffer), std::end(buffer)); + // Convert the seed output to a single state value. + state_type tmp = buffer[0]; + for (size_t i = 1; i < kBufferSize; i++) { + tmp <<= (sizeof(sequence_result_type) * 8); + tmp |= buffer[i]; + } + state_ = lcg(tmp + params_type::increment()); + } +}; + +// Parameterized implementation of the PCG 128-bit oneseq state. +// This provides state_type, multiplier, and increment for pcg_engine. +template +class pcg128_params { + public: +#if ABSL_HAVE_INTRINSIC_INT128 + using state_type = __uint128_t; + static inline constexpr state_type make_u128(uint64_t a, uint64_t b) { + return (static_cast<__uint128_t>(a) << 64) | b; + } +#else + using state_type = absl::uint128; + static inline constexpr state_type make_u128(uint64_t a, uint64_t b) { + return absl::MakeUint128(a, b); + } +#endif + + static inline constexpr state_type multiplier() { + return make_u128(kMultA, kMultB); + } + static inline constexpr state_type increment() { + return make_u128(kIncA, kIncB); + } +}; + +// Implementation of the PCG xsl_rr_128_64 128-bit mixing function, which +// accepts an input of state_type and mixes it into an output of result_type. +struct pcg_xsl_rr_128_64 { +#if ABSL_HAVE_INTRINSIC_INT128 + using state_type = __uint128_t; +#else + using state_type = absl::uint128; +#endif + using result_type = uint64_t; + + inline uint64_t operator()(state_type state) { + // This is equivalent to the xsl_rr_128_64 mixing function. +#if ABSL_HAVE_INTRINSIC_INT128 + uint64_t rotate = static_cast(state >> 122u); + state ^= state >> 64; + uint64_t s = static_cast(state); +#else + uint64_t h = Uint128High64(state); + uint64_t rotate = h >> 58u; + uint64_t s = Uint128Low64(state) ^ h; +#endif + return random_internal::rotr(s, rotate); + } +}; + +// Parameterized implementation of the PCG 64-bit oneseq state. +// This provides state_type, multiplier, and increment for pcg_engine. +template +class pcg64_params { + public: + using state_type = uint64_t; + static inline constexpr state_type multiplier() { return kMult; } + static inline constexpr state_type increment() { return kInc; } +}; + +// Implementation of the PCG xsh_rr_64_32 64-bit mixing function, which accepts +// an input of state_type and mixes it into an output of result_type. +struct pcg_xsh_rr_64_32 { + using state_type = uint64_t; + using result_type = uint32_t; + inline uint32_t operator()(uint64_t state) { + return random_internal::rotr( + static_cast(((state >> 18) ^ state) >> 27), state >> 59); + } +}; + +// Stable pcg_engine implementations: +// This is a 64-bit generator using 128-bits of state. +// The output sequence is equivalent to Melissa O'Neil's pcg64_oneseq. +using pcg64_2018_engine = pcg_engine< + random_internal::pcg128_params<0x2360ed051fc65da4ull, 0x4385df649fccf645ull, + 0x5851f42d4c957f2d, 0x14057b7ef767814f>, + random_internal::pcg_xsl_rr_128_64>; + +// This is a 32-bit generator using 64-bits of state. +// This is equivalent to Melissa O'Neil's pcg32_oneseq. +using pcg32_2018_engine = pcg_engine< + random_internal::pcg64_params<0x5851f42d4c957f2dull, 0x14057b7ef767814full>, + random_internal::pcg_xsh_rr_64_32>; + +} // namespace random_internal +} // namespace absl + +#endif // ABSL_RANDOM_PCG2018_ENGINE_H_ -- cgit 1.4.1