diff options
Diffstat (limited to 'third_party/abseil_cpp/absl/random/internal/pcg_engine.h')
| -rw-r--r-- | third_party/abseil_cpp/absl/random/internal/pcg_engine.h | 307 |
1 files changed, 0 insertions, 307 deletions
diff --git a/third_party/abseil_cpp/absl/random/internal/pcg_engine.h b/third_party/abseil_cpp/absl/random/internal/pcg_engine.h deleted file mode 100644 index 53c23fe1b4..0000000000 --- a/third_party/abseil_cpp/absl/random/internal/pcg_engine.h +++ /dev/null @@ -1,307 +0,0 @@ -// 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_INTERNAL_PCG_ENGINE_H_ -#define ABSL_RANDOM_INTERNAL_PCG_ENGINE_H_ - -#include <type_traits> - -#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 { -ABSL_NAMESPACE_BEGIN -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 <typename Params, typename Mix> -class pcg_engine { - static_assert(std::is_same<typename Params::state_type, - typename Mix::state_type>::value, - "Class-template absl::pcg_engine must be parameterized by " - "Params and Mix with identical state_type"); - - static_assert(std::is_unsigned<typename Mix::result_type>::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<result_type>::min)(); - } - - static constexpr result_type(max)() { - return (std::numeric_limits<result_type>::max)(); - } - - explicit pcg_engine(uint64_t seed_value = 0) { seed(seed_value); } - - template <class SeedSequence, - typename = typename absl::enable_if_t< - !std::is_same<SeedSequence, pcg_engine>::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 <class SeedSequence> - typename absl::enable_if_t< - !std::is_convertible<SeedSequence, uint64_t>::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 <class CharT, class Traits> - friend typename absl::enable_if_t<(sizeof(state_type) == 16), - std::basic_ostream<CharT, Traits>&> - operator<<( - std::basic_ostream<CharT, Traits>& os, // NOLINT(runtime/references) - const pcg_engine& engine) { - auto saver = random_internal::make_ostream_state_saver(os); - random_internal::stream_u128_helper<state_type> 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 <class CharT, class Traits> - friend typename absl::enable_if_t<(sizeof(state_type) <= 8), - std::basic_ostream<CharT, Traits>&> - operator<<( - std::basic_ostream<CharT, Traits>& 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 <class CharT, class Traits> - friend typename absl::enable_if_t<(sizeof(state_type) == 16), - std::basic_istream<CharT, Traits>&> - operator>>( - std::basic_istream<CharT, Traits>& is, // NOLINT(runtime/references) - pcg_engine& engine) { // NOLINT(runtime/references) - random_internal::stream_u128_helper<state_type> 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 <class CharT, class Traits> - friend typename absl::enable_if_t<(sizeof(state_type) <= 8), - std::basic_istream<CharT, Traits>&> - operator>>( - std::basic_istream<CharT, Traits>& 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 <class SeedSequence> - 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 <uint64_t kMultA, uint64_t kMultB, uint64_t kIncA, uint64_t kIncB> -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<uint64_t>(state >> 122u); - state ^= state >> 64; - uint64_t s = static_cast<uint64_t>(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 <uint64_t kMult, uint64_t kInc> -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<uint32_t>(((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 -ABSL_NAMESPACE_END -} // namespace absl - -#endif // ABSL_RANDOM_INTERNAL_PCG_ENGINE_H_ |