index_heap.h

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/*

Copyright (c) 2010--2011, Stephane Magnenat, ASL, ETHZ, Switzerland
You can contact the author at <stephane at magnenat dot net>

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      documentation and/or other materials provided with the distribution.
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      names of its contributors may be used to endorse or promote products
      derived from this software without specific prior written permission.

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*/

#ifndef __INDEX_HEAP_H
#define __INDEX_HEAP_H

#include "nabo.h"
#include <vector>
#include <algorithm>
#include <limits>
#include <iostream>

namespace Nabo
{

    template<typename IT, typename VT>
    struct IndexHeapSTL
    {
        typedef IT Index;
        typedef VT Value;
        
        struct Entry
        {
            IT index; 
            VT value; 
            
            Entry(const IT index, const VT value): index(index), value(value) {}
            friend bool operator<(const Entry& e0, const Entry& e1) { return e0.value < e1.value; }
        };
        typedef std::vector<Entry> Entries;
        typedef typename Eigen::Matrix<Index, Eigen::Dynamic, 1> IndexVector;
        typedef typename Eigen::Matrix<Value, Eigen::Dynamic, 1> ValueVector;
        
        Entries data;
        const size_t nbNeighbours;

        

        IndexHeapSTL(const size_t size):
            data(1, Entry(0, std::numeric_limits<VT>::infinity())),
            nbNeighbours(size)
        {
            data.reserve(size);
        }
        
        inline void reset()
        {
            data.clear();
            data.push_back(Entry(0, std::numeric_limits<VT>::infinity()));
        }
        

        inline const VT& headValue() const { return data.front().value; }
        

        inline void replaceHead(const Index index, const Value value)
        {

            if (data.size() == nbNeighbours)
            {   // we have enough neighbours to discard largest
                pop_heap(data.begin(), data.end());
                data.back() = Entry(index, value);
            }
            else
            {   // missing neighbours
                data.push_back(Entry(index, value));
            }
            // ensure heap
            push_heap(data.begin(), data.end());
        }
        
        inline void sort()
        {
            sort_heap (data.begin(), data.end());
        }
        

        template<typename DI, typename DV>
        inline void getData(const Eigen::MatrixBase<DI>& indices, const Eigen::MatrixBase<DV> & values) const
        {
            // note: we must implement this hack because of problem with reference to temporary
            // C++0x will solve this with rvalue
            // see: http://eigen.tuxfamily.org/dox-devel/TopicFunctionTakingEigenTypes.html
            // for more informations
            size_t i = 0;
            for (; i < data.size(); ++i)
            {
                const_cast<Eigen::MatrixBase<DI>&>(indices).coeffRef(i) = data[i].index;
                const_cast<Eigen::MatrixBase<DV>&>(values).coeffRef(i) = data[i].value;
            }
            for (; i < nbNeighbours; ++i)
            {
                const_cast<Eigen::MatrixBase<DI>&>(indices).coeffRef(i) = 0;
                const_cast<Eigen::MatrixBase<DV>&>(values).coeffRef(i) = std::numeric_limits<VT>::infinity();
            }
        }
        
#if 0


        inline IndexVector getIndexes() const
        {
            IndexVector indexes(data.capacity());
            size_t i = 0;
            for (; i < data.size(); ++i)
                indexes.coeffRef(i) = data[i].index;
            for (; i < data.capacity(); ++i)
                indexes.coeffRef(i) = 0;
            return indexes;
        }
#endif
    };
    
#if 0


    template<typename IT, typename VT>
    struct IndexHeapBruteForceVector
    {
        typedef IT Index;
        typedef VT Value;
        
        struct Entry
        {
            IT index; 
            VT value;  
            
            Entry(const IT index, const VT value): index(index), value(value) {} 
            friend bool operator<(const Entry& e0, const Entry& e1) { return e0.value < e1.value; }
        };
        typedef std::vector<Entry> Entries;
        typedef typename Eigen::Matrix<Index, Eigen::Dynamic, 1> IndexVector;
        
        Entries data;
        const VT& headValueRef;
        const size_t sizeMinusOne;
        

        IndexHeapBruteForceVector(const size_t size):
            data(size, Entry(0, std::numeric_limits<VT>::infinity())),
            headValueRef((data.end() - 1)->value),
            sizeMinusOne(data.size() - 1)
        {
        }
        
        inline void reset()
        {
            for (typename Entries::iterator it(data.begin()); it != data.end(); ++it)
                it->value = std::numeric_limits<VT>::infinity();
        }
        

        inline const VT& headValue() const { return data[0].value; }
        

        inline void replaceHead(const Index index, const Value value)
        {
            register size_t i = 0;
            for (; i < sizeMinusOne; ++i)
            {
                if (data[i + 1].value > value)
                    data[i] = data[i + 1];
                else
                    break;
            }
            data[i].value = value;
            data[i].index = index;
        }
        
        inline void sort()
        {
            // no need to sort as data are already sorted
        }
        

        inline IndexVector getIndexes() const
        {
            IndexVector indexes(data.size());
            for (size_t i = 0; i < data.size(); ++i)
                indexes.coeffRef(i) = data[sizeMinusOne-i].index;
            return indexes;
        }
    };
#endif
    

    template<typename IT, typename VT>
    struct IndexHeapBruteForceVector
    {
        typedef IT Index;
        typedef VT Value;
        
        struct Entry
        {
            IT index; 
            VT value;  
            
            Entry(const IT index, const VT value): index(index), value(value) {} 
            friend bool operator<(const Entry& e0, const Entry& e1) { return e0.value < e1.value; }
        };
        typedef std::vector<Entry> Entries;
        typedef typename Eigen::Matrix<Index, Eigen::Dynamic, 1> IndexVector;
        typedef typename Eigen::Matrix<Value, Eigen::Dynamic, 1> ValueVector;
        
        Entries data;
        const VT& headValueRef;
        const size_t sizeMinusOne;
        

        IndexHeapBruteForceVector(const size_t size):
        data(size, Entry(0, std::numeric_limits<VT>::infinity())),
        headValueRef((data.end() - 1)->value),
        sizeMinusOne(data.size() - 1)
        {
        }
        
        inline void reset()
        {
            for (typename Entries::iterator it(data.begin()); it != data.end(); ++it)
                it->value = std::numeric_limits<VT>::infinity();
        }
        

        inline const VT& headValue() const { return headValueRef; }
        

        inline void replaceHead(const Index index, const Value value)
        {
            register size_t i;
            for (i = sizeMinusOne; i > 0; --i)
            {
                if (data[i-1].value > value)
                    data[i] = data[i-1];
                else
                    break;
            }
            data[i].value = value;
            data[i].index = index;
        }
        
        inline void sort()
        {
            // no need to sort as data are already sorted
        }
        

        template<typename DI, typename DV>
        inline void getData(const Eigen::MatrixBase<DI>& indices, const Eigen::MatrixBase<DV> & values) const
        {
            // note: we must implement this hack because of problem with reference to temporary
            // C++0x will solve this with rvalue
            // see: http://eigen.tuxfamily.org/dox-devel/TopicFunctionTakingEigenTypes.html
            // for more informations
            for (size_t i = 0; i < data.size(); ++i)
            {
                const_cast<Eigen::MatrixBase<DI>&>(indices).coeffRef(i) = data[i].index;
                const_cast<Eigen::MatrixBase<DV>&>(values).coeffRef(i) = data[i].value;
            }
        }
#if 0


        inline IndexVector getIndexes() const
        {
            IndexVector indexes(data.size());
            for (size_t i = 0; i < data.size(); ++i)
                indexes.coeffRef(i) = data[i].index;
            return indexes;
        }
#endif
    };
}

#endif // __INDEX_HEAP_H