ompl/datastructures/NearestNeighborsSqrtApprox.h
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00034 
00035 /* Author: Ioan Sucan */
00036 
00037 #ifndef OMPL_DATASTRUCTURES_NEAREST_NEIGHBORS_SQRT_APPROX_
00038 #define OMPL_DATASTRUCTURES_NEAREST_NEIGHBORS_SQRT_APPROX_
00039 
00040 #include "ompl/datastructures/NearestNeighborsLinear.h"
00041 #include <algorithm>
00042 #include <cmath>
00043 
00044 namespace ompl
00045 {
00056     template<typename _T>
00057     class NearestNeighborsSqrtApprox : public NearestNeighborsLinear<_T>
00058     {
00059     public:
00060         NearestNeighborsSqrtApprox() : NearestNeighborsLinear<_T>(), checks_(0), offset_(0)
00061         {
00062         }
00063 
00064         virtual ~NearestNeighborsSqrtApprox()
00065         {
00066         }
00067 
00068         virtual void clear()
00069         {
00070             NearestNeighborsLinear<_T>::clear();
00071             checks_ = 0;
00072             offset_ = 0;
00073         }
00074 
00075         virtual void add(const _T &data)
00076         {
00077             NearestNeighborsLinear<_T>::add(data);
00078             updateCheckCount();
00079         }
00080 
00081         virtual void add(const std::vector<_T> &data)
00082         {
00083             NearestNeighborsLinear<_T>::add(data);
00084             updateCheckCount();
00085         }
00086 
00087         virtual bool remove(const _T &data)
00088         {
00089             bool result = NearestNeighborsLinear<_T>::remove(data);
00090             if (result)
00091                 updateCheckCount();
00092             return result;
00093         }
00094 
00095         virtual _T nearest(const _T &data) const
00096         {
00097             const std::size_t n = NearestNeighborsLinear<_T>::data_.size();
00098             std::size_t pos = n;
00099 
00100             if (checks_ > 0 && n > 0)
00101             {
00102                 double dmin = 0.0;
00103                 for (std::size_t j = 0 ; j < checks_ ; ++j)
00104                 {
00105                     std::size_t i = (j * checks_ + offset_) % n;
00106 
00107                     double distance = NearestNeighbors<_T>::distFun_(NearestNeighborsLinear<_T>::data_[i], data);
00108                     if (pos == n || dmin > distance)
00109                     {
00110                         pos = i;
00111                         dmin = distance;
00112                     }
00113                 }
00114                 offset_ = (offset_ + 1) % checks_;
00115             }
00116             if (pos != n)
00117                 return NearestNeighborsLinear<_T>::data_[pos];
00118 
00119             throw Exception("No elements found in nearest neighbors data structure");
00120         }
00121 
00122     protected:
00123 
00125         inline void updateCheckCount()
00126         {
00127             checks_ = 1 + (std::size_t)floor(sqrt((double)NearestNeighborsLinear<_T>::data_.size()));
00128         }
00129 
00131         std::size_t         checks_;
00132 
00134         mutable std::size_t offset_;
00135 
00136     };
00137 
00138 }
00139 
00140 #endif
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