0266c9d969
The new numbering uses the partition information to sort border nodes first to compactify storages that need access indexed by border node ID. We also get an optimized cache performance for free sincr we can also recursively sort the nodes by cell ID. This implements issue #3779.
45 lines
1.2 KiB
C++
45 lines
1.2 KiB
C++
#ifndef OSRM_UTIL_PERMUTATION_HPP
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#define OSRM_UTIL_PERMUTATION_HPP
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#include "util/integer_range.hpp"
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#include <vector>
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namespace osrm
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{
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namespace util
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{
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template <typename RandomAccesIterator, typename IndexT>
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void inplacePermutation(RandomAccesIterator begin,
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RandomAccesIterator end,
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const std::vector<IndexT> &old_to_new)
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{
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std::size_t size = std::distance(begin, end);
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BOOST_ASSERT(old_to_new.size() == size);
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// we need a little bit auxililary space since we need to mark
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// replaced elements in a non-destructive way
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std::vector<bool> was_replaced(size, false);
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for (auto index : util::irange<IndexT>(0, size))
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{
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if (was_replaced[index])
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continue;
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// iterate over a cycle in the permutation
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auto buffer = begin[index];
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auto old_index = index;
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auto new_index = old_to_new[old_index];
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for (; new_index != index; old_index = new_index, new_index = old_to_new[new_index])
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{
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was_replaced[old_index] = true;
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std::swap(buffer, begin[new_index]);
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}
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was_replaced[old_index] = true;
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std::swap(buffer, begin[index]);
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}
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}
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}
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}
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#endif
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