void FruchtermanReingold::make_initialisations(double bl, DPoint d_l_c, int grid_quot)
{
grid_quotient(grid_quot);
down_left_corner = d_l_c; //export this two values from FMMM
boxlength = bl;
}
FruchtermanReingold:: FruchtermanReingold()
{
grid_quotient(2);
}
void FruchtermanReingold::calculate_approx_repulsive_forces(
const Graph &G,
NodeArray<NodeAttributes> &A,
NodeArray<DPoint>& F_rep)
{
//GRID algorithm by Fruchterman & Reingold
numexcept N;
List<IPoint> neighbour_boxes;
List<node> neighbour_box;
IPoint act_neighbour_box;
IPoint neighbour;
DPoint f_rep_u_on_v;
DPoint vector_v_minus_u;
DPoint nullpoint(0, 0);
DPoint pos_u, pos_v;
double norm_v_minus_u;
double scalar;
int i, j, act_i, act_j, k, l, length;
double gridboxlength;//length of a box in the GRID
//init F_rep
for (node v : G.nodes)
F_rep[v] = nullpoint;
//init max_gridindex and set contained_nodes;
max_gridindex = static_cast<int> (sqrt(double(G.numberOfNodes())) / grid_quotient()) - 1;
max_gridindex = ((max_gridindex > 0) ? max_gridindex : 0);
Array2D<List<node> > contained_nodes(0, max_gridindex, 0, max_gridindex);
for (i = 0; i <= max_gridindex; i++)
for (j = 0; j <= max_gridindex; j++)
{
contained_nodes(i, j).clear();
}
gridboxlength = boxlength / (max_gridindex + 1);
for (node v : G.nodes)
{
double x = A[v].get_x() - down_left_corner.m_x;//shift comput. box to nullpoint
double y = A[v].get_y() - down_left_corner.m_y;
int x_index = static_cast<int>(x / gridboxlength);
int y_index = static_cast<int>(y / gridboxlength);
contained_nodes(x_index, y_index).pushBack(v);
}
//force calculation
for (i = 0; i <= max_gridindex; i++)
for (j = 0; j <= max_gridindex; j++)
{
//step1: calculate forces inside contained_nodes(i,j)
length = contained_nodes(i, j).size();
Array<node> nodearray_i_j(length + 1);
k = 1;
for (node v : contained_nodes(i, j))
{
nodearray_i_j[k] = v;
k++;
}
for (k = 1; k < length; k++)
for (l = k + 1; l <= length; l++)
{
node u = nodearray_i_j[k];
node v = nodearray_i_j[l];
pos_u = A[u].get_position();
pos_v = A[v].get_position();
if (pos_u == pos_v)
{//if2 (Exception handling if two nodes have the same position)
pos_u = N.choose_distinct_random_point_in_radius_epsilon(pos_u);
}//if2
vector_v_minus_u = pos_v - pos_u;
norm_v_minus_u = vector_v_minus_u.norm();
if (!N.f_rep_near_machine_precision(norm_v_minus_u, f_rep_u_on_v))
{
scalar = f_rep_scalar(norm_v_minus_u) / norm_v_minus_u;
f_rep_u_on_v.m_x = scalar * vector_v_minus_u.m_x;
f_rep_u_on_v.m_y = scalar * vector_v_minus_u.m_y;
}
F_rep[v] = F_rep[v] + f_rep_u_on_v;
F_rep[u] = F_rep[u] - f_rep_u_on_v;
}
//step 2: calculated forces to nodes in neighbour boxes
//find_neighbour_boxes
neighbour_boxes.clear();
for (k = i - 1; k <= i + 1; k++)
for (l = j - 1; l <= j + 1; l++)
if ((k >= 0) && (l >= 0) && (k <= max_gridindex) && (l <= max_gridindex))
{
neighbour.m_x = k;
neighbour.m_y = l;
if ((k != i) || (l != j))
neighbour_boxes.pushBack(neighbour);
}
//forget neighbour_boxes that already had access to this box
for (const IPoint &act_neighbour_box : neighbour_boxes)
{
act_i = act_neighbour_box.m_x;
act_j = act_neighbour_box.m_y;
if ((act_j == j + 1) || ((act_j == j) && (act_i == i + 1)))
{
for (node v : contained_nodes(i, j)) {
for (node u : contained_nodes(act_i, act_j))
{
pos_u = A[u].get_position();
pos_v = A[v].get_position();
if (pos_u == pos_v)
{// (Exception handling if two nodes have the same position)
pos_u = N.choose_distinct_random_point_in_radius_epsilon(pos_u);
}
vector_v_minus_u = pos_v - pos_u;
norm_v_minus_u = vector_v_minus_u.norm();
if (!N.f_rep_near_machine_precision(norm_v_minus_u, f_rep_u_on_v))
{
scalar = f_rep_scalar(norm_v_minus_u) / norm_v_minus_u;
f_rep_u_on_v.m_x = scalar * vector_v_minus_u.m_x;
f_rep_u_on_v.m_y = scalar * vector_v_minus_u.m_y;
}
F_rep[v] = F_rep[v] + f_rep_u_on_v;
F_rep[u] = F_rep[u] - f_rep_u_on_v;
}
}
}
}
}
}