DTreeForceTypes.h

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#pragma once
 
#include <cmath>
#include <type_traits>
 
namespace ogdf {
namespace energybased {
namespace dtree {
 
template<int Dim>
inline typename std::enable_if<Dim != 2, double>::type computeDeltaAndDistance(const double a[Dim],
        const double b[Dim], double delta[Dim]) {
    // distance var
    double dist = 0;
 
    // for all dim
    for (int d = 0; d < Dim; d++) {
        // delta in d dim
        delta[d] = a[d] - b[d];
 
        // squared distance sum
        dist += delta[d] * delta[d];
    }
 
    // distance square root
    return sqrt(dist);
}
 
template<int Dim>
inline typename std::enable_if<Dim == 2, double>::type computeDeltaAndDistance(const double a[Dim],
        const double b[Dim], double delta[Dim]) {
    // delta in d dim
    delta[0] = a[0] - b[0];
    delta[1] = a[1] - b[1];
 
    // distance square root
    return sqrt(delta[0] * delta[0] + delta[1] * delta[1]);
}
 
template<int Dim, int K>
inline typename std::enable_if<Dim != 2 || (K != 1 && K != 2), void>::type RepForceFunctionNewton(
        double dist, double& force, double& force_prime) {
    // distance square root
    dist = dist + 0.1;
 
    double t = dist;
    for (int i = 1; i < K; i++) {
        t *= dist;
    }
 
    force = 1.0 / (t);
    force_prime = (double)(K) / (t * dist);
}
 
template<int Dim, int K>
inline typename std::enable_if<Dim == 2 && K == 2, void>::type RepForceFunctionNewton(double dist,
        double& force, double& force_prime) {
    // distance square root
    dist = dist + 0.1;
    force_prime = 2.0 / (dist * dist * dist);
    force = force_prime * dist * 0.5;
}
 
template<int Dim, int K>
inline typename std::enable_if<Dim == 2 && K == 1, void>::type RepForceFunctionNewton(double dist,
        double& force, double& force_prime) {
    // distance square root
    dist = dist + 0.1;
    force_prime = 1.0 / (dist * dist);
    force = 1.0 / (dist);
}
 
template<int Dim>
inline void AttrForceFunctionLog(double dist, double& force, double& force_prime) {
    // distance square root
    force = log(dist / 1.0);
    force_prime = 1.0 / dist;
}
 
template<int Dim, int K>
inline typename std::enable_if<Dim != 2 || (K != 1 && K != 2), void>::type AttrForceFunctionPow(
        double dist, double& force, double& force_prime) {
    // distance square root
    dist = dist + 0.1;
 
    double t = dist;
    for (int i = 1; i < K; i++) {
        t *= dist;
    }
 
    force = t;
    force_prime = (double)(K) * (t / dist);
}
 
template<int Dim, int K>
inline typename std::enable_if<Dim == 2 && K == 2, void>::type AttrForceFunctionPow(double dist,
        double& force, double& force_prime) {
    // distance square root
    dist = dist + 0.1;
 
    force = dist * dist;
    force_prime = 2.0 * dist;
}
 
template<int Dim, int K>
inline typename std::enable_if<Dim == 2 && K == 1, void>::type AttrForceFunctionPow(double dist,
        double& force, double& force_prime) {
    // distance square root
    dist = dist + 0.1;
 
    force = dist;
    force_prime = 1.0;
}
 
#if 0
template<int Dim>
inline void RepForceFunctionInvGauss(const double a[Dim], const double b[Dim], double result[Dim])
{
    // the range of the repulsive force
    const double force_range = 10.0;
 
    // the amount of repulsive force
    const double force_amount = 20.0;
 
    // vector from b to a
    double delta[Dim];
 
    // distance var
    double dist = 0;
 
    // for all dim
    for (int d = 0; d < Dim; d++) {
        // delta in d dim
        delta[d] = a[d] - b[d];
 
        // squared distance sum
        dist += delta[d] * delta[d];
    }
 
    // distance square root
    dist =  sqrt(dist);
 
    // force function
    double f = (exp(- (dist * dist) / force_range ) * force_amount);
#   if 0
    double f = exp(-dist * dist * 0.01) * 10.0) / dist;
#   endif
 
 
    // compute the force vector for each dim
    for (int d = 0; d < Dim; d++) {
        result[d] = delta[d] * f/dist;
    };
}
#endif
 
}
}
}