chomp_cost.cpp

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/* Author: Mrinal Kalakrishnan */

#include <chomp_motion_planner/chomp_cost.h>
#include <chomp_motion_planner/chomp_utils.h>
#include <eigen3/Eigen/LU>

using namespace Eigen;
using namespace std;

namespace chomp
{
ChompCost::ChompCost(const ChompTrajectory& trajectory, int joint_number, const std::vector<double>& derivative_costs,
                     double ridge_factor)
{
  int num_vars_all = trajectory.getNumPoints();
  int num_vars_free = num_vars_all - 2 * (DIFF_RULE_LENGTH - 1);
  MatrixXd diff_matrix = MatrixXd::Zero(num_vars_all, num_vars_all);
  quad_cost_full_ = MatrixXd::Zero(num_vars_all, num_vars_all);

  // construct the quad cost for all variables, as a sum of squared differentiation matrices
  double multiplier = 1.0;
  for (unsigned int i = 0; i < derivative_costs.size(); i++)
  {
    multiplier *= trajectory.getDiscretization();
    diff_matrix = getDiffMatrix(num_vars_all, &DIFF_RULES[i][0]);
    quad_cost_full_ += (derivative_costs[i] * multiplier) * (diff_matrix.transpose() * diff_matrix);
  }
  quad_cost_full_ += MatrixXd::Identity(num_vars_all, num_vars_all) * ridge_factor;

  // extract the quad cost just for the free variables:
  quad_cost_ = quad_cost_full_.block(DIFF_RULE_LENGTH - 1, DIFF_RULE_LENGTH - 1, num_vars_free, num_vars_free);

  // invert the matrix:
  quad_cost_inv_ = quad_cost_.inverse();

  // cout << quad_cost_inv_ << endl;
}

Eigen::MatrixXd ChompCost::getDiffMatrix(int size, const double* diff_rule) const
{
  MatrixXd matrix = MatrixXd::Zero(size, size);
  for (int i = 0; i < size; i++)
  {
    for (int j = -DIFF_RULE_LENGTH / 2; j <= DIFF_RULE_LENGTH / 2; j++)
    {
      int index = i + j;
      if (index < 0)
        continue;
      if (index >= size)
        continue;
      matrix(i, index) = diff_rule[j + DIFF_RULE_LENGTH / 2];
    }
  }
  return matrix;
}

double ChompCost::getMaxQuadCostInvValue() const
{
  return quad_cost_inv_.maxCoeff();
}

void ChompCost::scale(double scale)
{
  double inv_scale = 1.0 / scale;
  quad_cost_inv_ *= inv_scale;
  quad_cost_ *= scale;
  quad_cost_full_ *= scale;
}

ChompCost::~ChompCost()
{
}
}