DTreeWSPD.h

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#pragma once
 
#include <ogdf/basic/basic.h>
#include <ogdf/energybased/dtree/DTree.h>
 
#include <algorithm>
#include <utility>
 
namespace ogdf {
namespace energybased {
namespace dtree {
 
class IWSPD {
public:
    virtual void onWellSeparatedPair(int aIndex, int bIndex) = 0;
};
 
template<int Dim>
class DTreeWSPD {
public:
    using IntType = unsigned int;
    using Tree = DTree<IntType, Dim>;
 
    explicit DTreeWSPD(int numPoints);
 
    ~DTreeWSPD();
 
    struct NodeData {
        double x[Dim];
 
        double min_x[Dim];
 
        double max_x[Dim];
 
        double radius_sq;
    };
 
    struct PointData {
        double x[Dim];
    };
 
    void update();
 
    const Tree& tree() const { return *m_pTree; };
 
    const NodeData& node(int i) const { return m_nodeData[i]; };
 
    void setPoint(int i, int d, double coord);
 
    const PointData& point(int i) const { return m_pointData[i]; };
 
    // temp function for
    void computeWSPD(IWSPD* m_pIWSPD);
 
    double separationFactor() const { return m_wspdSeparationFactor; };
 
    void setSeparationFactor(double s) { m_wspdSeparationFactor = s; };
 
protected:
    IWSPD* m_pIWSPD = nullptr;
 
    NodeData& node(int i) { return m_nodeData[i]; };
 
    void updateBoundingBox();
 
    void updateTreeGridPoints();
 
    void updateTreeNodeGeometry();
 
    void updateTreeNodeGeometry(int curr);
 
    void wspdRecursive(int a);
 
    void wspdRecursive(int a, int b);
 
    bool areWellSeparated(int a, int b) const;
 
    void allocate();
 
    void deallocate();
 
    int m_numPoints;
 
    double m_wspdSeparationFactor;
 
    double m_wspdSeparationFactorPlus2Squared_cached;
 
    Tree* m_pTree = nullptr;
 
    NodeData* m_nodeData = nullptr;
 
    PointData* m_pointData = nullptr;
 
    double m_bboxMin[Dim];
 
    double m_bboxMax[Dim];
};
 
template<int Dim>
DTreeWSPD<Dim>::DTreeWSPD(int numPoints)
    : m_numPoints(numPoints)
    , m_wspdSeparationFactor(1.0)
    , m_wspdSeparationFactorPlus2Squared_cached(9.0) {
    // get the memory
    allocate();
 
    // init arrays
    for (int i = 0; i < Dim; i++) {
        m_bboxMin[i] = m_bboxMax[i] = 0.0;
    }
}
 
template<int Dim>
DTreeWSPD<Dim>::~DTreeWSPD() {
    // free the mem
    deallocate();
}
 
template<int Dim>
void DTreeWSPD<Dim>::allocate() {
    m_pTree = new Tree(m_numPoints);
    m_nodeData = new NodeData[m_pTree->maxNumNodes()];
    m_pointData = new PointData[m_numPoints];
}
 
template<int Dim>
void DTreeWSPD<Dim>::deallocate() {
    delete m_pTree;
    delete[] m_nodeData;
    delete[] m_pointData;
}
 
template<int Dim>
void DTreeWSPD<Dim>::update() {
    // update the bounding box of the point set
    updateBoundingBox();
 
    // update grid points inside the quadtree
    updateTreeGridPoints();
 
    // rebuild the tree
    m_pTree->build();
 
    // compute center, radius and bbox for each node
    updateTreeNodeGeometry();
}
 
template<int Dim>
void DTreeWSPD<Dim>::computeWSPD(IWSPD* pIWSPD) {
    m_pIWSPD = pIWSPD;
 
    // update this cached value for the well-sep test
    const double s = (m_wspdSeparationFactor + 2.0);
 
    // precompute this
    m_wspdSeparationFactorPlus2Squared_cached = s * s;
 
    // go ahead with the decomposition
    wspdRecursive(m_pTree->rootIndex());
}
 
// the unary recursive function generating the binary calls
template<int Dim>
void DTreeWSPD<Dim>::wspdRecursive(int curr) {
    // iterate over all ordered pairs of children
    for (int i = 0; i < m_pTree->numChilds(curr); i++) {
        // the first child index
        const int first_child = m_pTree->child(curr, i);
 
        // the second loop for the pair
        for (int j = i + 1; j < m_pTree->numChilds(curr); j++) {
            // the second child index
            const int second_child = m_pTree->child(curr, j);
 
            // call for each ordered pair the binary function
            wspdRecursive(first_child, second_child);
        }
 
        // now do all this for every child
        wspdRecursive(first_child);
    }
}
 
template<int Dim>
void DTreeWSPD<Dim>::wspdRecursive(int a, int b) {
    if (areWellSeparated(a, b)) {
        // far enough away => approx
        if (m_pIWSPD) {
            m_pIWSPD->onWellSeparatedPair(a, b);
        }
    } else {
        // two cells are too close
        int small_node = a;
        int large_node = b;
 
        // make sure the small one is not the bigger one
        if (node(small_node).radius_sq > node(large_node).radius_sq) {
            std::swap(small_node, large_node);
        }
 
        // split the bigger one
        for (int i = 0; i < tree().numChilds(large_node); ++i) {
            // recurse on the child
            wspdRecursive(small_node, tree().child(large_node, i));
        }
    }
}
 
template<int Dim>
bool DTreeWSPD<Dim>::areWellSeparated(int a, int b) const {
    // take the bigger radius
    double r_max_sq = std::max(node(a).radius_sq, node(b).radius_sq);
 
    // compute the square distance
    double dist_sq = 0.0;
 
    // the d^2 loop
    for (int d = 0; d < Dim; d++) {
        double dx = node(a).x[d] - node(b).x[d];
        dist_sq += dx * dx;
    }
 
    // two circles are well separated iff d - 2r > sr
    // where d is the distance between the two centers
    // (not the distance of circles!)
    // this ws <=> d > (s + 2)r
    // more efficient: d^2 > (s + 2)^2 r^2
    // d_sq > (s^2 + 4s + 4) * r_max
#if 0
#   if 0
    const double s = (m_wspdSeparationFactor + 2.0);
    return dist_sq > (m_wspdSeparationFactor * m_wspdSeparationFactor + 4.0 * m_wspdSeparationFactor + 4) * r_max * r_max;
#   else
    return dist_sq > s * s * r_max_sq;
#   endif
#else
    return dist_sq > m_wspdSeparationFactorPlus2Squared_cached * r_max_sq;
#endif
}
 
template<>
bool DTreeWSPD<2>::areWellSeparated(int a, int b) const {
    // take the bigger radius
    double r_max_sq = std::max(node(a).radius_sq, node(b).radius_sq);
 
    // compute the square distance
    double dx_0 = node(a).x[0] - node(b).x[0];
    double dx_1 = node(a).x[1] - node(b).x[1];
    double dist_sq = dx_0 * dx_0 + dx_1 * dx_1;
 
    // compare the sq distance
    return dist_sq > m_wspdSeparationFactorPlus2Squared_cached * r_max_sq;
}
 
template<>
bool DTreeWSPD<3>::areWellSeparated(int a, int b) const {
    // take the bigger radius
    double r_max_sq = std::max(node(a).radius_sq, node(b).radius_sq);
 
    // compute the square distance
    double dx_0 = node(a).x[0] - node(b).x[0];
    double dx_1 = node(a).x[1] - node(b).x[1];
    double dx_2 = node(a).x[2] - node(b).x[2];
    double dist_sq = dx_0 * dx_0 + dx_1 * dx_1 + dx_2 * dx_2;
 
    // compare the sq distance
    return dist_sq > m_wspdSeparationFactorPlus2Squared_cached * r_max_sq;
}
 
template<int Dim>
void DTreeWSPD<Dim>::setPoint(int i, int d, double coord) {
    m_pointData[i].x[d] = coord;
}
 
template<int Dim>
void DTreeWSPD<Dim>::updateBoundingBox() {
    if (!m_numPoints) {
        return;
    }
 
    // initial values
    for (int d = 0; d < Dim; d++) {
        m_bboxMin[d] = m_bboxMax[d] = point(0).x[d];
    }
 
    // no magic here
    for (int i = 1; i < m_numPoints; i++) {
        for (int d = 0; d < Dim; d++) {
            m_bboxMin[d] = std::min(m_bboxMin[d], point(i).x[d]);
            m_bboxMax[d] = std::max(m_bboxMax[d], point(i).x[d]);
        }
    }
}
 
// updates the integer grid points in the quadtree
template<int Dim>
void DTreeWSPD<Dim>::updateTreeGridPoints() {
    for (int d = 0; d < Dim; d++) {
        double noise_max = (m_bboxMax[d] - m_bboxMin[d]) * 0.25;
        m_bboxMax[d] += randomDouble(0.0, noise_max);
        m_bboxMin[d] -= randomDouble(0.0, noise_max);
    }
    // lets assume the bbox is updated. find the longest side
    double quad_size = m_bboxMax[0] - m_bboxMin[0];
    for (int d = 1; d < Dim; d++) {
        quad_size = std::max(quad_size, m_bboxMax[d] - m_bboxMin[d]);
    }
 
    const double factor = (double)(0xffffffff);
 
    double scale = factor / quad_size;
    // iterate over all points
    for (int i = 0; i < m_numPoints; i++) {
        for (int d = 0; d < Dim; d++) {
            // put it in the bounding square
#if 0
            double nx = ((point(i).x[d] - m_bboxMin[d] + 0.01) / quad_size + 0.02);
#endif
            double nx = ((point(i).x[d] - m_bboxMin[d]) * scale);
 
            // dirty put on grid here
            unsigned int ix = static_cast<unsigned int>(nx); //nx * (double)(unsigned int)(0x1fffffff);
 
            // set the point coord
            m_pTree->setPoint(i, d, ix);
        }
    }
}
 
template<int Dim>
void DTreeWSPD<Dim>::updateTreeNodeGeometry() {
    updateTreeNodeGeometry(m_pTree->rootIndex());
}
 
// updates the geometry of the quadtree nodes
template<int Dim>
void DTreeWSPD<Dim>::updateTreeNodeGeometry(int curr) {
    // if this is an inner node
    if (m_pTree->numChilds(curr)) {
        // init with the bbox of the first child
 
        // iterate over the rest of the children
        for (int i = 0; i < m_pTree->numChilds(curr); i++) {
            // the child index
            const int child = m_pTree->child(curr, i);
 
            // compute the size of the subtree
            updateTreeNodeGeometry(child);
 
            // lazy set the first
            if (!i) {
                for (int d = 0; d < Dim; d++) {
                    node(curr).min_x[d] = node(child).min_x[d];
                    node(curr).max_x[d] = node(child).max_x[d];
                }
            } else {
                for (int d = 0; d < Dim; d++) {
                    node(curr).min_x[d] = std::min(node(curr).min_x[d], node(child).min_x[d]);
                    node(curr).max_x[d] = std::max(node(curr).max_x[d], node(child).max_x[d]);
                }
            }
        };
    } else { // else it is a leaf
        // init from first point
        for (int d = 0; d < Dim; d++) {
            node(curr).min_x[d] = node(curr).max_x[d] = point(tree().point(curr, 0)).x[d];
        }
 
        // and the remaining points
        for (int i = 1; i < tree().numPoints(curr); ++i) {
            for (int d = 0; d < Dim; d++) {
                node(curr).min_x[d] =
                        std::min(node(curr).min_x[d], point(tree().point(curr, i)).x[d]);
                node(curr).max_x[d] =
                        std::max(node(curr).max_x[d], point(tree().point(curr, i)).x[d]);
            }
        }
    }
 
    // init the radius
    node(curr).radius_sq = 0.0;
 
    // compute the center and radius of the rect
    for (int d = 0; d < Dim; d++) {
        node(curr).x[d] = (node(curr).min_x[d] + node(curr).max_x[d]) * 0.5;
        double s_x = (node(curr).max_x[d] - node(curr).min_x[d]);
        node(curr).radius_sq += s_x * s_x;
    }
 
    // and the smallest enclosing circle radius squared
    node(curr).radius_sq *= 0.25; // sqrt(node(curr).radius) * 0.5 squared;
}
 
}
}
}