c34026b101
note: done using ```sh git grep -l "2010-2024 Google" | xargs sed -i 's/2010-2024 Google/2010-2025 Google/' ```
57 lines
2.0 KiB
C++
57 lines
2.0 KiB
C++
// Copyright 2010-2025 Google LLC
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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#include "ortools/base/constant_divisor.h"
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#include <cstdint>
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#include <limits>
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#include "absl/log/check.h"
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#include "absl/numeric/int128.h"
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namespace util {
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namespace math {
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// Fast div/mod implementation based on
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// "Faster Remainder by Direct Computation: Applications to Compilers and
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// Software Libraries" Daniel Lemire, Owen Kaser, Nathan Kurz arXiv:1902.01961
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ConstantDivisor<uint64_t>::ConstantDivisor(value_type d)
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: ConstantDivisorBase((absl::Uint128Max() / d) + 1, d) {
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CHECK_GT(d, 1) << "ConstantDivisor<uint64_t> only supports denominators > 1.";
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}
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// If we hardcode shift_amount to 32, the 32-bit formula is:
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// magic_number = 2 ^ 64 / d
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// value / d = value * magic_number >> 64
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//
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// One caveat is that for d == 1, magic_number takes 65 bits overflowing a
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// uint64_t. So, we again disallow inputs with d == 1.
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ConstantDivisor<uint32_t>::ConstantDivisor(value_type d)
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: ConstantDivisorBase((std::numeric_limits<MagicValueType>::max() / d) + 1,
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d) {
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CHECK_GT(d, 1) << "ConstantDivisor<uint32_t> only supports denominators > 1.";
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}
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ConstantDivisor<uint16_t>::ConstantDivisor(value_type d)
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: ConstantDivisorBase((MagicValueType{1} << kShift) / d + 1, d) {
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CHECK_GT(d, 0);
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}
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ConstantDivisor<uint8_t>::ConstantDivisor(value_type d)
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: ConstantDivisorBase((MagicValueType{1} << kShift) / d + 1, d) {
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CHECK_GT(d, 0);
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}
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} // namespace math
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} // namespace util
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