Neighbors find_neighbors_bruteforce_impl(const RandomAccessIterator& begin, const RandomAccessIterator& end,
Callback callback, IndexType k)
{
timed_context context("Distance sorting based neighbors search");
typedef std::pair<RandomAccessIterator, ScalarType> DistanceRecord;
typedef std::vector<DistanceRecord> Distances;
Neighbors neighbors;
neighbors.reserve(end-begin);
for (RandomAccessIterator iter=begin; iter!=end; ++iter)
{
Distances distances;
for (RandomAccessIterator around_iter=begin; around_iter!=end; ++around_iter)
distances.push_back(std::make_pair(around_iter, callback.distance(iter,around_iter)));
std::nth_element(distances.begin(),distances.begin()+k+1,distances.end(),
distances_comparator<DistanceRecord>());
LocalNeighbors local_neighbors;
local_neighbors.reserve(k);
for (typename Distances::const_iterator neighbors_iter=distances.begin();
neighbors_iter!=distances.begin()+k+1; ++neighbors_iter)
{
if (neighbors_iter->first != iter)
local_neighbors.push_back(neighbors_iter->first - begin);
}
neighbors.push_back(local_neighbors);
}
return neighbors;
}
Neighbors find_neighbors_vptree_impl(const RandomAccessIterator& begin, const RandomAccessIterator& end,
Callback callback, IndexType k)
{
timed_context context("VP-Tree based neighbors search");
Neighbors neighbors;
neighbors.reserve(end-begin);
VantagePointTree<RandomAccessIterator,Callback> tree(begin,end,callback);
for (RandomAccessIterator i=begin; i!=end; ++i)
{
LocalNeighbors local_neighbors = tree.search(i,k+1);
std::remove(local_neighbors.begin(),local_neighbors.end(),i-begin);
neighbors.push_back(local_neighbors);
}
return neighbors;
}
