mirror of
https://github.com/ceres-solver/ceres-solver.git
synced 2026-08-29 16:40:38 +08:00
Sergiu Deitsch
3d3d6ed71b
pair_hash.h uses std::size_t and std::hash but does not include the corresponding headers <cstddef> and <functional>. Change-Id: I194a5c76e8f50b1574e1359f616351581033c576
119 lines
4.0 KiB
C++
119 lines
4.0 KiB
C++
// Ceres Solver - A fast non-linear least squares minimizer
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// Copyright 2022 Google Inc. All rights reserved.
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// http://ceres-solver.org/
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//
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// Redistribution and use in source and binary forms, with or without
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// modification, are permitted provided that the following conditions are met:
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//
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// * Redistributions of source code must retain the above copyright notice,
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// this list of conditions and the following disclaimer.
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// * Redistributions in binary form must reproduce the above copyright notice,
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// this list of conditions and the following disclaimer in the documentation
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// and/or other materials provided with the distribution.
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// * Neither the name of Google Inc. nor the names of its contributors may be
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// used to endorse or promote products derived from this software without
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// specific prior written permission.
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//
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// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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// ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
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// LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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// CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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// SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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// CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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// ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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// POSSIBILITY OF SUCH DAMAGE.
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//
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// Author: keir@google.com (Keir Mierle)
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//
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// A hasher for std::pair<T, T>.
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#ifndef CERES_INTERNAL_PAIR_HASH_H_
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#define CERES_INTERNAL_PAIR_HASH_H_
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#include <cstddef>
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#include <cstdint>
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#include <functional>
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#include <utility>
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#include "ceres/internal/export.h"
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namespace ceres {
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namespace internal {
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#if defined(_WIN32) && !defined(__MINGW64__) && !defined(__MINGW32__)
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#define GG_LONGLONG(x) x##I64
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#define GG_ULONGLONG(x) x##UI64
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#else
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#define GG_LONGLONG(x) x##LL
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#define GG_ULONGLONG(x) x##ULL
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#endif
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// The hash function is due to Bob Jenkins (see
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// http://burtleburtle.net/bob/hash/index.html). Each mix takes 36 instructions,
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// in 18 cycles if you're lucky. On x86 architectures, this requires 45
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// instructions in 27 cycles, if you're lucky.
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//
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// clang-format off
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//
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// 32bit version
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inline void hash_mix(uint32_t& a, uint32_t& b, uint32_t& c) {
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a -= b; a -= c; a ^= (c>>13);
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b -= c; b -= a; b ^= (a<<8);
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c -= a; c -= b; c ^= (b>>13);
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a -= b; a -= c; a ^= (c>>12);
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b -= c; b -= a; b ^= (a<<16);
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c -= a; c -= b; c ^= (b>>5);
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a -= b; a -= c; a ^= (c>>3);
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b -= c; b -= a; b ^= (a<<10);
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c -= a; c -= b; c ^= (b>>15);
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}
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// 64bit version
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inline void hash_mix(uint64_t& a, uint64_t& b, uint64_t& c) {
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a -= b; a -= c; a ^= (c>>43);
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b -= c; b -= a; b ^= (a<<9);
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c -= a; c -= b; c ^= (b>>8);
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a -= b; a -= c; a ^= (c>>38);
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b -= c; b -= a; b ^= (a<<23);
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c -= a; c -= b; c ^= (b>>5);
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a -= b; a -= c; a ^= (c>>35);
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b -= c; b -= a; b ^= (a<<49);
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c -= a; c -= b; c ^= (b>>11);
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}
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// clang-format on
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inline uint32_t Hash32NumWithSeed(uint32_t num, uint32_t c) {
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// The golden ratio; an arbitrary value.
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uint32_t b = 0x9e3779b9UL;
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hash_mix(num, b, c);
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return c;
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}
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inline uint64_t Hash64NumWithSeed(uint64_t num, uint64_t c) {
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// More of the golden ratio.
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uint64_t b = GG_ULONGLONG(0xe08c1d668b756f82);
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hash_mix(num, b, c);
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return c;
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}
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// Hasher for STL pairs. Requires hashers for both members to be defined.
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struct pair_hash {
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public:
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template <typename T>
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std::size_t operator()(const std::pair<T, T>& p) const {
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const std::size_t h1 = std::hash<T>()(p.first);
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const std::size_t h2 = std::hash<T>()(p.second);
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// The decision below is at compile time
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return (sizeof(h1) <= sizeof(uint32_t)) ? Hash32NumWithSeed(h1, h2)
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: Hash64NumWithSeed(h1, h2);
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}
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};
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} // namespace internal
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} // namespace ceres
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#endif // CERES_INTERNAL_PAIR_HASH_H_
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