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Diffstat (limited to 'third_party/abseil_cpp/absl/random/internal/fastmath.h')
-rw-r--r-- | third_party/abseil_cpp/absl/random/internal/fastmath.h | 74 |
1 files changed, 0 insertions, 74 deletions
diff --git a/third_party/abseil_cpp/absl/random/internal/fastmath.h b/third_party/abseil_cpp/absl/random/internal/fastmath.h deleted file mode 100644 index 6baeb5a7c917..000000000000 --- a/third_party/abseil_cpp/absl/random/internal/fastmath.h +++ /dev/null @@ -1,74 +0,0 @@ -// 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_INTERNAL_FASTMATH_H_ -#define ABSL_RANDOM_INTERNAL_FASTMATH_H_ - -// This file contains fast math functions (bitwise ops as well as some others) -// which are implementation details of various absl random number distributions. - -#include <cassert> -#include <cmath> -#include <cstdint> - -#include "absl/base/internal/bits.h" - -namespace absl { -ABSL_NAMESPACE_BEGIN -namespace random_internal { - -// Returns the position of the first bit set. -inline int LeadingSetBit(uint64_t n) { - return 64 - base_internal::CountLeadingZeros64(n); -} - -// Compute log2(n) using integer operations. -// While std::log2 is more accurate than std::log(n) / std::log(2), for -// very large numbers--those close to std::numeric_limits<uint64_t>::max() - 2, -// for instance--std::log2 rounds up rather than down, which introduces -// definite skew in the results. -inline int IntLog2Floor(uint64_t n) { - return (n <= 1) ? 0 : (63 - base_internal::CountLeadingZeros64(n)); -} -inline int IntLog2Ceil(uint64_t n) { - return (n <= 1) ? 0 : (64 - base_internal::CountLeadingZeros64(n - 1)); -} - -inline double StirlingLogFactorial(double n) { - assert(n >= 1); - // Using Stirling's approximation. - constexpr double kLog2PI = 1.83787706640934548356; - const double logn = std::log(n); - const double ninv = 1.0 / static_cast<double>(n); - return n * logn - n + 0.5 * (kLog2PI + logn) + (1.0 / 12.0) * ninv - - (1.0 / 360.0) * ninv * ninv * ninv; -} - -// Rotate value right. -// -// We only implement the uint32_t / uint64_t versions because -// 1) those are the only ones we use, and -// 2) those are the only ones where clang detects the rotate idiom correctly. -inline constexpr uint32_t rotr(uint32_t value, uint8_t bits) { - return (value >> (bits & 31)) | (value << ((-bits) & 31)); -} -inline constexpr uint64_t rotr(uint64_t value, uint8_t bits) { - return (value >> (bits & 63)) | (value << ((-bits) & 63)); -} - -} // namespace random_internal -ABSL_NAMESPACE_END -} // namespace absl - -#endif // ABSL_RANDOM_INTERNAL_FASTMATH_H_ |