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Diffstat (limited to 'boost/sort/spreadsort/detail/integer_sort.hpp')
| -rw-r--r-- | boost/sort/spreadsort/detail/integer_sort.hpp | 494 |
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diff --git a/boost/sort/spreadsort/detail/integer_sort.hpp b/boost/sort/spreadsort/detail/integer_sort.hpp new file mode 100644 index 0000000000..bc14b3585c --- /dev/null +++ b/boost/sort/spreadsort/detail/integer_sort.hpp @@ -0,0 +1,494 @@ +// Details for templated Spreadsort-based integer_sort.
+
+// Copyright Steven J. Ross 2001 - 2014.
+// Distributed under the Boost Software License, Version 1.0.
+// (See accompanying file LICENSE_1_0.txt or copy at
+// http://www.boost.org/LICENSE_1_0.txt)
+
+// See http://www.boost.org/libs/sort for library home page.
+
+/*
+Some improvements suggested by:
+Phil Endecott and Frank Gennari
+*/
+
+#ifndef BOOST_SORT_SPREADSORT_DETAIL_INTEGER_SORT_HPP
+#define BOOST_SORT_SPREADSORT_DETAIL_INTEGER_SORT_HPP
+#include <algorithm>
+#include <vector>
+#include <limits>
+#include <functional>
+#include <boost/static_assert.hpp>
+#include <boost/serialization/static_warning.hpp>
+#include <boost/utility/enable_if.hpp>
+#include <boost/sort/spreadsort/detail/constants.hpp>
+#include <boost/sort/spreadsort/detail/spreadsort_common.hpp>
+#include <boost/cstdint.hpp>
+
+namespace boost {
+namespace sort {
+namespace spreadsort {
+ namespace detail {
+ // Return true if the list is sorted. Otherwise, find the minimum and
+ // maximum using <.
+ template <class RandomAccessIter>
+ inline bool
+ is_sorted_or_find_extremes(RandomAccessIter current, RandomAccessIter last,
+ RandomAccessIter & max, RandomAccessIter & min)
+ {
+ min = max = current;
+ //This assumes we have more than 1 element based on prior checks.
+ while (!(*(current + 1) < *current)) {
+ //If everything is in sorted order, return
+ if (++current == last - 1)
+ return true;
+ }
+
+ //The maximum is the last sorted element
+ max = current;
+ //Start from the first unsorted element
+ while (++current < last) {
+ if (*max < *current)
+ max = current;
+ else if (*current < *min)
+ min = current;
+ }
+ return false;
+ }
+
+ // Return true if the list is sorted. Otherwise, find the minimum and
+ // maximum.
+ // Use a user-defined comparison operator
+ template <class RandomAccessIter, class Compare>
+ inline bool
+ is_sorted_or_find_extremes(RandomAccessIter current, RandomAccessIter last,
+ RandomAccessIter & max, RandomAccessIter & min, Compare comp)
+ {
+ min = max = current;
+ while (!comp(*(current + 1), *current)) {
+ //If everything is in sorted order, return
+ if (++current == last - 1)
+ return true;
+ }
+
+ //The maximum is the last sorted element
+ max = current;
+ while (++current < last) {
+ if (comp(*max, *current))
+ max = current;
+ else if (comp(*current, *min))
+ min = current;
+ }
+ return false;
+ }
+
+ //Gets a non-negative right bit shift to operate as a logarithmic divisor
+ template<unsigned log_mean_bin_size>
+ inline int
+ get_log_divisor(size_t count, int log_range)
+ {
+ int log_divisor;
+ //If we can finish in one iteration without exceeding either
+ //(2 to the max_finishing_splits) or n bins, do so
+ if ((log_divisor = log_range - rough_log_2_size(count)) <= 0 &&
+ log_range <= max_finishing_splits)
+ log_divisor = 0;
+ else {
+ //otherwise divide the data into an optimized number of pieces
+ log_divisor += log_mean_bin_size;
+ //Cannot exceed max_splits or cache misses slow down bin lookups
+ if ((log_range - log_divisor) > max_splits)
+ log_divisor = log_range - max_splits;
+ }
+ return log_divisor;
+ }
+
+ //Implementation for recursive integer sorting
+ template <class RandomAccessIter, class Div_type, class Size_type>
+ inline void
+ spreadsort_rec(RandomAccessIter first, RandomAccessIter last,
+ std::vector<RandomAccessIter> &bin_cache, unsigned cache_offset
+ , size_t *bin_sizes)
+ {
+ //This step is roughly 10% of runtime, but it helps avoid worst-case
+ //behavior and improve behavior with real data
+ //If you know the maximum and minimum ahead of time, you can pass those
+ //values in and skip this step for the first iteration
+ RandomAccessIter max, min;
+ if (is_sorted_or_find_extremes(first, last, max, min))
+ return;
+ RandomAccessIter * target_bin;
+ unsigned log_divisor = get_log_divisor<int_log_mean_bin_size>(
+ last - first, rough_log_2_size(Size_type((*max >> 0) - (*min >> 0))));
+ Div_type div_min = *min >> log_divisor;
+ Div_type div_max = *max >> log_divisor;
+ unsigned bin_count = unsigned(div_max - div_min) + 1;
+ unsigned cache_end;
+ RandomAccessIter * bins =
+ size_bins(bin_sizes, bin_cache, cache_offset, cache_end, bin_count);
+
+ //Calculating the size of each bin; this takes roughly 10% of runtime
+ for (RandomAccessIter current = first; current != last;)
+ bin_sizes[size_t((*(current++) >> log_divisor) - div_min)]++;
+ //Assign the bin positions
+ bins[0] = first;
+ for (unsigned u = 0; u < bin_count - 1; u++)
+ bins[u + 1] = bins[u] + bin_sizes[u];
+
+ RandomAccessIter nextbinstart = first;
+ //Swap into place
+ //This dominates runtime, mostly in the swap and bin lookups
+ for (unsigned u = 0; u < bin_count - 1; ++u) {
+ RandomAccessIter * local_bin = bins + u;
+ nextbinstart += bin_sizes[u];
+ //Iterating over each element in this bin
+ for (RandomAccessIter current = *local_bin; current < nextbinstart;
+ ++current) {
+ //Swapping elements in current into place until the correct
+ //element has been swapped in
+ for (target_bin = (bins + ((*current >> log_divisor) - div_min));
+ target_bin != local_bin;
+ target_bin = bins + ((*current >> log_divisor) - div_min)) {
+ //3-way swap; this is about 1% faster than a 2-way swap
+ //The main advantage is less copies are involved per item
+ //put in the correct place
+ typename std::iterator_traits<RandomAccessIter>::value_type tmp;
+ RandomAccessIter b = (*target_bin)++;
+ RandomAccessIter * b_bin = bins + ((*b >> log_divisor) - div_min);
+ if (b_bin != local_bin) {
+ RandomAccessIter c = (*b_bin)++;
+ tmp = *c;
+ *c = *b;
+ }
+ else
+ tmp = *b;
+ *b = *current;
+ *current = tmp;
+ }
+ }
+ *local_bin = nextbinstart;
+ }
+ bins[bin_count - 1] = last;
+
+ //If we've bucketsorted, the array is sorted and we should skip recursion
+ if (!log_divisor)
+ return;
+ //log_divisor is the remaining range; calculating the comparison threshold
+ size_t max_count =
+ get_min_count<int_log_mean_bin_size, int_log_min_split_count,
+ int_log_finishing_count>(log_divisor);
+
+ //Recursing
+ RandomAccessIter lastPos = first;
+ for (unsigned u = cache_offset; u < cache_end; lastPos = bin_cache[u],
+ ++u) {
+ Size_type count = bin_cache[u] - lastPos;
+ //don't sort unless there are at least two items to Compare
+ if (count < 2)
+ continue;
+ //using std::sort if its worst-case is better
+ if (count < max_count)
+ std::sort(lastPos, bin_cache[u]);
+ else
+ spreadsort_rec<RandomAccessIter, Div_type, Size_type>(lastPos,
+ bin_cache[u],
+ bin_cache,
+ cache_end,
+ bin_sizes);
+ }
+ }
+
+ //Generic bitshift-based 3-way swapping code
+ template <class RandomAccessIter, class Div_type, class Right_shift>
+ inline void inner_swap_loop(RandomAccessIter * bins,
+ const RandomAccessIter & next_bin_start, unsigned ii, Right_shift &rshift
+ , const unsigned log_divisor, const Div_type div_min)
+ {
+ RandomAccessIter * local_bin = bins + ii;
+ for (RandomAccessIter current = *local_bin; current < next_bin_start;
+ ++current) {
+ for (RandomAccessIter * target_bin =
+ (bins + (rshift(*current, log_divisor) - div_min));
+ target_bin != local_bin;
+ target_bin = bins + (rshift(*current, log_divisor) - div_min)) {
+ typename std::iterator_traits<RandomAccessIter>::value_type tmp;
+ RandomAccessIter b = (*target_bin)++;
+ RandomAccessIter * b_bin =
+ bins + (rshift(*b, log_divisor) - div_min);
+ //Three-way swap; if the item to be swapped doesn't belong
+ //in the current bin, swap it to where it belongs
+ if (b_bin != local_bin) {
+ RandomAccessIter c = (*b_bin)++;
+ tmp = *c;
+ *c = *b;
+ }
+ //Note: we could increment current once the swap is done in this case
+ //but that seems to impair performance
+ else
+ tmp = *b;
+ *b = *current;
+ *current = tmp;
+ }
+ }
+ *local_bin = next_bin_start;
+ }
+
+ //Standard swapping wrapper for ascending values
+ template <class RandomAccessIter, class Div_type, class Right_shift>
+ inline void swap_loop(RandomAccessIter * bins,
+ RandomAccessIter & next_bin_start, unsigned ii, Right_shift &rshift
+ , const size_t *bin_sizes
+ , const unsigned log_divisor, const Div_type div_min)
+ {
+ next_bin_start += bin_sizes[ii];
+ inner_swap_loop<RandomAccessIter, Div_type, Right_shift>(bins,
+ next_bin_start, ii, rshift, log_divisor, div_min);
+ }
+
+ //Functor implementation for recursive sorting
+ template <class RandomAccessIter, class Div_type, class Right_shift,
+ class Compare, class Size_type, unsigned log_mean_bin_size,
+ unsigned log_min_split_count, unsigned log_finishing_count>
+ inline void
+ spreadsort_rec(RandomAccessIter first, RandomAccessIter last,
+ std::vector<RandomAccessIter> &bin_cache, unsigned cache_offset
+ , size_t *bin_sizes, Right_shift rshift, Compare comp)
+ {
+ RandomAccessIter max, min;
+ if (is_sorted_or_find_extremes(first, last, max, min, comp))
+ return;
+ unsigned log_divisor = get_log_divisor<log_mean_bin_size>(last - first,
+ rough_log_2_size(Size_type(rshift(*max, 0) - rshift(*min, 0))));
+ Div_type div_min = rshift(*min, log_divisor);
+ Div_type div_max = rshift(*max, log_divisor);
+ unsigned bin_count = unsigned(div_max - div_min) + 1;
+ unsigned cache_end;
+ RandomAccessIter * bins = size_bins(bin_sizes, bin_cache, cache_offset,
+ cache_end, bin_count);
+
+ //Calculating the size of each bin
+ for (RandomAccessIter current = first; current != last;)
+ bin_sizes[unsigned(rshift(*(current++), log_divisor) - div_min)]++;
+ bins[0] = first;
+ for (unsigned u = 0; u < bin_count - 1; u++)
+ bins[u + 1] = bins[u] + bin_sizes[u];
+
+ //Swap into place
+ RandomAccessIter next_bin_start = first;
+ for (unsigned u = 0; u < bin_count - 1; ++u)
+ swap_loop<RandomAccessIter, Div_type, Right_shift>(bins, next_bin_start,
+ u, rshift, bin_sizes, log_divisor, div_min);
+ bins[bin_count - 1] = last;
+
+ //If we've bucketsorted, the array is sorted
+ if (!log_divisor)
+ return;
+
+ //Recursing
+ size_t max_count = get_min_count<log_mean_bin_size, log_min_split_count,
+ log_finishing_count>(log_divisor);
+ RandomAccessIter lastPos = first;
+ for (unsigned u = cache_offset; u < cache_end; lastPos = bin_cache[u],
+ ++u) {
+ size_t count = bin_cache[u] - lastPos;
+ if (count < 2)
+ continue;
+ if (count < max_count)
+ std::sort(lastPos, bin_cache[u], comp);
+ else
+ spreadsort_rec<RandomAccessIter, Div_type, Right_shift, Compare,
+ Size_type, log_mean_bin_size, log_min_split_count, log_finishing_count>
+ (lastPos, bin_cache[u], bin_cache, cache_end, bin_sizes, rshift, comp);
+ }
+ }
+
+ //Functor implementation for recursive sorting with only Shift overridden
+ template <class RandomAccessIter, class Div_type, class Right_shift,
+ class Size_type, unsigned log_mean_bin_size,
+ unsigned log_min_split_count, unsigned log_finishing_count>
+ inline void
+ spreadsort_rec(RandomAccessIter first, RandomAccessIter last,
+ std::vector<RandomAccessIter> &bin_cache, unsigned cache_offset
+ , size_t *bin_sizes, Right_shift rshift)
+ {
+ RandomAccessIter max, min;
+ if (is_sorted_or_find_extremes(first, last, max, min))
+ return;
+ unsigned log_divisor = get_log_divisor<log_mean_bin_size>(last - first,
+ rough_log_2_size(Size_type(rshift(*max, 0) - rshift(*min, 0))));
+ Div_type div_min = rshift(*min, log_divisor);
+ Div_type div_max = rshift(*max, log_divisor);
+ unsigned bin_count = unsigned(div_max - div_min) + 1;
+ unsigned cache_end;
+ RandomAccessIter * bins = size_bins(bin_sizes, bin_cache, cache_offset,
+ cache_end, bin_count);
+
+ //Calculating the size of each bin
+ for (RandomAccessIter current = first; current != last;)
+ bin_sizes[unsigned(rshift(*(current++), log_divisor) - div_min)]++;
+ bins[0] = first;
+ for (unsigned u = 0; u < bin_count - 1; u++)
+ bins[u + 1] = bins[u] + bin_sizes[u];
+
+ //Swap into place
+ RandomAccessIter nextbinstart = first;
+ for (unsigned ii = 0; ii < bin_count - 1; ++ii)
+ swap_loop<RandomAccessIter, Div_type, Right_shift>(bins, nextbinstart,
+ ii, rshift, bin_sizes, log_divisor, div_min);
+ bins[bin_count - 1] = last;
+
+ //If we've bucketsorted, the array is sorted
+ if (!log_divisor)
+ return;
+
+ //Recursing
+ size_t max_count = get_min_count<log_mean_bin_size, log_min_split_count,
+ log_finishing_count>(log_divisor);
+ RandomAccessIter lastPos = first;
+ for (unsigned u = cache_offset; u < cache_end; lastPos = bin_cache[u],
+ ++u) {
+ size_t count = bin_cache[u] - lastPos;
+ if (count < 2)
+ continue;
+ if (count < max_count)
+ std::sort(lastPos, bin_cache[u]);
+ else
+ spreadsort_rec<RandomAccessIter, Div_type, Right_shift, Size_type,
+ log_mean_bin_size, log_min_split_count, log_finishing_count>(lastPos,
+ bin_cache[u], bin_cache, cache_end, bin_sizes, rshift);
+ }
+ }
+
+ //Holds the bin vector and makes the initial recursive call
+ template <class RandomAccessIter, class Div_type>
+ //Only use spreadsort if the integer can fit in a size_t
+ inline typename boost::enable_if_c< sizeof(Div_type) <= sizeof(size_t),
+ void >::type
+ integer_sort(RandomAccessIter first, RandomAccessIter last, Div_type)
+ {
+ size_t bin_sizes[1 << max_finishing_splits];
+ std::vector<RandomAccessIter> bin_cache;
+ spreadsort_rec<RandomAccessIter, Div_type, size_t>(first, last,
+ bin_cache, 0, bin_sizes);
+ }
+
+ //Holds the bin vector and makes the initial recursive call
+ template <class RandomAccessIter, class Div_type>
+ //Only use spreadsort if the integer can fit in a uintmax_t
+ inline typename boost::enable_if_c< (sizeof(Div_type) > sizeof(size_t))
+ && sizeof(Div_type) <= sizeof(boost::uintmax_t), void >::type
+ integer_sort(RandomAccessIter first, RandomAccessIter last, Div_type)
+ {
+ size_t bin_sizes[1 << max_finishing_splits];
+ std::vector<RandomAccessIter> bin_cache;
+ spreadsort_rec<RandomAccessIter, Div_type, boost::uintmax_t>(first,
+ last, bin_cache, 0, bin_sizes);
+ }
+
+ template <class RandomAccessIter, class Div_type>
+ inline typename boost::disable_if_c< sizeof(Div_type) <= sizeof(size_t)
+ || sizeof(Div_type) <= sizeof(boost::uintmax_t), void >::type
+ //defaulting to std::sort when integer_sort won't work
+ integer_sort(RandomAccessIter first, RandomAccessIter last, Div_type)
+ {
+ //Warning that we're using std::sort, even though integer_sort was called
+ BOOST_STATIC_WARNING( sizeof(Div_type) <= sizeof(size_t) );
+ std::sort(first, last);
+ }
+
+
+ //Same for the full functor version
+ template <class RandomAccessIter, class Div_type, class Right_shift,
+ class Compare>
+ //Only use spreadsort if the integer can fit in a size_t
+ inline typename boost::enable_if_c< sizeof(Div_type) <= sizeof(size_t),
+ void >::type
+ integer_sort(RandomAccessIter first, RandomAccessIter last, Div_type,
+ Right_shift shift, Compare comp)
+ {
+ size_t bin_sizes[1 << max_finishing_splits];
+ std::vector<RandomAccessIter> bin_cache;
+ spreadsort_rec<RandomAccessIter, Div_type, Right_shift, Compare,
+ size_t, int_log_mean_bin_size, int_log_min_split_count,
+ int_log_finishing_count>
+ (first, last, bin_cache, 0, bin_sizes, shift, comp);
+ }
+
+ template <class RandomAccessIter, class Div_type, class Right_shift,
+ class Compare>
+ //Only use spreadsort if the integer can fit in a uintmax_t
+ inline typename boost::enable_if_c< (sizeof(Div_type) > sizeof(size_t))
+ && sizeof(Div_type) <= sizeof(boost::uintmax_t), void >::type
+ integer_sort(RandomAccessIter first, RandomAccessIter last, Div_type,
+ Right_shift shift, Compare comp)
+ {
+ size_t bin_sizes[1 << max_finishing_splits];
+ std::vector<RandomAccessIter> bin_cache;
+ spreadsort_rec<RandomAccessIter, Div_type, Right_shift, Compare,
+ boost::uintmax_t, int_log_mean_bin_size,
+ int_log_min_split_count, int_log_finishing_count>
+ (first, last, bin_cache, 0, bin_sizes, shift, comp);
+ }
+
+ template <class RandomAccessIter, class Div_type, class Right_shift,
+ class Compare>
+ inline typename boost::disable_if_c< sizeof(Div_type) <= sizeof(size_t)
+ || sizeof(Div_type) <= sizeof(boost::uintmax_t), void >::type
+ //defaulting to std::sort when integer_sort won't work
+ integer_sort(RandomAccessIter first, RandomAccessIter last, Div_type,
+ Right_shift shift, Compare comp)
+ {
+ //Warning that we're using std::sort, even though integer_sort was called
+ BOOST_STATIC_WARNING( sizeof(Div_type) <= sizeof(size_t) );
+ std::sort(first, last, comp);
+ }
+
+
+ //Same for the right shift version
+ template <class RandomAccessIter, class Div_type, class Right_shift>
+ //Only use spreadsort if the integer can fit in a size_t
+ inline typename boost::enable_if_c< sizeof(Div_type) <= sizeof(size_t),
+ void >::type
+ integer_sort(RandomAccessIter first, RandomAccessIter last, Div_type,
+ Right_shift shift)
+ {
+ size_t bin_sizes[1 << max_finishing_splits];
+ std::vector<RandomAccessIter> bin_cache;
+ spreadsort_rec<RandomAccessIter, Div_type, Right_shift, size_t,
+ int_log_mean_bin_size, int_log_min_split_count,
+ int_log_finishing_count>
+ (first, last, bin_cache, 0, bin_sizes, shift);
+ }
+
+ template <class RandomAccessIter, class Div_type, class Right_shift>
+ //Only use spreadsort if the integer can fit in a uintmax_t
+ inline typename boost::enable_if_c< (sizeof(Div_type) > sizeof(size_t))
+ && sizeof(Div_type) <= sizeof(boost::uintmax_t), void >::type
+ integer_sort(RandomAccessIter first, RandomAccessIter last, Div_type,
+ Right_shift shift)
+ {
+ size_t bin_sizes[1 << max_finishing_splits];
+ std::vector<RandomAccessIter> bin_cache;
+ spreadsort_rec<RandomAccessIter, Div_type, Right_shift,
+ boost::uintmax_t, int_log_mean_bin_size,
+ int_log_min_split_count, int_log_finishing_count>
+ (first, last, bin_cache, 0, bin_sizes, shift);
+ }
+
+ template <class RandomAccessIter, class Div_type, class Right_shift>
+ inline typename boost::disable_if_c< sizeof(Div_type) <= sizeof(size_t)
+ || sizeof(Div_type) <= sizeof(boost::uintmax_t), void >::type
+ //defaulting to std::sort when integer_sort won't work
+ integer_sort(RandomAccessIter first, RandomAccessIter last, Div_type,
+ Right_shift shift)
+ {
+ //Warning that we're using std::sort, even though integer_sort was called
+ BOOST_STATIC_WARNING( sizeof(Div_type) <= sizeof(size_t) );
+ std::sort(first, last);
+ }
+ }
+}
+}
+}
+
+#endif
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