mirror of
https://gitlab.kitware.com/vtk/vtk-m
synced 2024-10-08 11:29:02 +00:00
187 lines
5.4 KiB
C++
187 lines
5.4 KiB
C++
//============================================================================
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// Copyright (c) Kitware, Inc.
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// All rights reserved.
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// See LICENSE.txt for details.
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//
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// This software is distributed WITHOUT ANY WARRANTY; without even
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// the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
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// PURPOSE. See the above copyright notice for more information.
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//============================================================================
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/* The MIT License
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Copyright (c) 2016 Dinghua Li <voutcn@gmail.com>
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Permission is hereby granted, free of charge, to any person obtaining
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a copy of this software and associated documentation files (the
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"Software"), to deal in the Software without restriction, including
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without limitation the rights to use, copy, modify, merge, publish,
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distribute, sublicense, and/or sell copies of the Software, and to
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permit persons to whom the Software is furnished to do so, subject to
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the following conditions:
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The above copyright notice and this permission notice shall be
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included in all copies or substantial portions of the Software.
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THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
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MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
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NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
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BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
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ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
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CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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SOFTWARE.
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*/
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#ifndef KXSORT_H__
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#define KXSORT_H__
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#include <algorithm>
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#include <iterator>
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namespace kx
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{
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static constexpr int kRadixBits = 8;
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static constexpr size_t kInsertSortThreshold = 64;
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static constexpr int kRadixMask = (1 << kRadixBits) - 1;
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static constexpr int kRadixBin = 1 << kRadixBits;
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//================= HELPING FUNCTIONS ====================
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template <class T>
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struct RadixTraitsUnsigned
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{
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static constexpr int nBytes = sizeof(T);
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int kth_byte(const T& x, int k) { return (x >> (kRadixBits * k)) & kRadixMask; }
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bool compare(const T& x, const T& y) { return x < y; }
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};
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template <class T>
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struct RadixTraitsSigned
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{
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static constexpr int nBytes = sizeof(T);
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static const T kMSB = T(0x80) << ((sizeof(T) - 1) * 8);
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int kth_byte(const T& x, int k) { return ((x ^ kMSB) >> (kRadixBits * k)) & kRadixMask; }
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bool compare(const T& x, const T& y) { return x < y; }
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};
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template <class RandomIt, class ValueType, class RadixTraits>
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inline void insert_sort_core_(RandomIt s, RandomIt e, RadixTraits radix_traits)
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{
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for (RandomIt i = s + 1; i < e; ++i)
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{
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if (radix_traits.compare(*i, *(i - 1)))
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{
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RandomIt j;
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ValueType tmp = *i;
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*i = *(i - 1);
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for (j = i - 1; j > s && radix_traits.compare(tmp, *(j - 1)); --j)
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{
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*j = *(j - 1);
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}
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*j = tmp;
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}
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}
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}
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template <class RandomIt, class ValueType, class RadixTraits, int kWhichByte>
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inline void radix_sort_core_(RandomIt s, RandomIt e, RadixTraits radix_traits)
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{
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RandomIt last_[kRadixBin + 1];
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RandomIt* last = last_ + 1;
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size_t count[kRadixBin] = { 0 };
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for (RandomIt i = s; i < e; ++i)
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{
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++count[radix_traits.kth_byte(*i, kWhichByte)];
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}
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last_[0] = last_[1] = s;
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for (int i = 1; i < kRadixBin; ++i)
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{
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last[i] = last[i - 1] + count[i - 1];
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}
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for (int i = 0; i < kRadixBin; ++i)
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{
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RandomIt end = last[i - 1] + count[i];
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if (end == e)
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{
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last[i] = e;
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break;
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}
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while (last[i] != end)
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{
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ValueType swapper = *last[i];
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int tag = radix_traits.kth_byte(swapper, kWhichByte);
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if (tag != i)
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{
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do
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{
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std::swap(swapper, *last[tag]++);
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} while ((tag = radix_traits.kth_byte(swapper, kWhichByte)) != i);
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*last[i] = swapper;
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}
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++last[i];
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}
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}
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if (kWhichByte > 0)
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{
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for (int i = 0; i < kRadixBin; ++i)
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{
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if (count[i] > kInsertSortThreshold)
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{
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radix_sort_core_<RandomIt, ValueType, RadixTraits, (kWhichByte > 0 ? (kWhichByte - 1) : 0)>(
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last[i - 1], last[i], radix_traits);
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}
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else if (count[i] > 1)
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{
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insert_sort_core_<RandomIt, ValueType, RadixTraits>(last[i - 1], last[i], radix_traits);
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}
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}
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}
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}
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template <class RandomIt, class ValueType, class RadixTraits>
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inline void radix_sort_entry_(RandomIt s, RandomIt e, ValueType*, RadixTraits radix_traits)
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{
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if (e - s <= (int)kInsertSortThreshold)
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insert_sort_core_<RandomIt, ValueType, RadixTraits>(s, e, radix_traits);
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else
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radix_sort_core_<RandomIt, ValueType, RadixTraits, RadixTraits::nBytes - 1>(s, e, radix_traits);
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}
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template <class RandomIt, class ValueType>
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inline void radix_sort_entry_(RandomIt s, RandomIt e, ValueType*)
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{
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if (ValueType(-1) > ValueType(0))
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{
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radix_sort_entry_(s, e, (ValueType*)(0), RadixTraitsUnsigned<ValueType>());
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}
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else
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{
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radix_sort_entry_(s, e, (ValueType*)(0), RadixTraitsSigned<ValueType>());
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}
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}
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//================= INTERFACES ====================
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template <class RandomIt, class RadixTraits>
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inline void radix_sort(RandomIt s, RandomIt e, RadixTraits radix_traits)
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{
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typename std::iterator_traits<RandomIt>::value_type* dummy(0);
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radix_sort_entry_(s, e, dummy, radix_traits);
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}
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template <class RandomIt>
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inline void radix_sort(RandomIt s, RandomIt e)
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{
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typename std::iterator_traits<RandomIt>::value_type* dummy(0);
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radix_sort_entry_(s, e, dummy);
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}
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}
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#endif
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