vector_bound_box.h

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/*
 * Copyright (c) 2018, The Regents of the University of California (Regents).
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 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS AS IS
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 * Please contact the author(s) of this library if you have any questions.
 * Authors: David Fridovich-Keil   ( dfk@eecs.berkeley.edu )
 */

//
// Class to specify a box constraint on a vector-valued control variable.
//

#ifndef FASTRACK_CONTROL_VECTOR_BOUND_BOX_H
#define FASTRACK_CONTROL_VECTOR_BOUND_BOX_H

#include <fastrack/control/control_bound.h>
#include <fastrack/control/scalar_bound_interval.h>

namespace fastrack {
namespace control {

class VectorBoundBox : public ControlBound<VectorXd> {
 public:
  ~VectorBoundBox() {}
  explicit VectorBoundBox(const VectorXd& min, const VectorXd& max)
      : min_(min), max_(max) {
    if (min_.size() != max_.size())
      throw std::runtime_error("Inconsistent bound dimensions.");
  }

  // Assume 'params' is laid out such that the first half of the parameters
  // form the 'min_' and the second form the 'max_'.
  explicit VectorBoundBox(const std::vector<double>& params) {
    if (!params.size() || params.size() & 1)
      throw std::runtime_error("Incorrect number of parameters.");

    const size_t dimension = params.size() >> 1;

    min_.resize(dimension);
    for (size_t ii = 0; ii < dimension; ii++) min_(ii) = params[ii];

    max_.resize(dimension);
    for (size_t ii = 0; ii < dimension; ii++) max_(ii) = params[dimension + ii];
  }

  // Accessors.
  inline const VectorXd& Min() const { return min_; }
  inline const VectorXd& Max() const { return max_; }

  // Custom definition of copy-assign operator.
  VectorBoundBox& operator=(const VectorBoundBox& other) {
    if (&other == this) return *this;

    min_ = other.min_;
    max_ = other.max_;
    return *this;
  }

  // Derived classes must be able to check whether a query is inside the bound.
  inline bool Contains(const VectorXd& query) const {
    if (min_.size() != query.size())
      throw std::runtime_error("Incorrect query dimension.");

    for (size_t ii = 0; ii < min_.size(); ii++) {
      if (min_(ii) > query(ii) || query(ii) > max_(ii)) return false;
    }

    return true;
  }

  // Derived classes must be able to compute the projection of a vector
  // (represented as the templated type) onto the surface of the bound.
  // NOTE: this is basically solving an LP with the bound as the feasible
  // set and the query as the coefficients.
  inline VectorXd ProjectToSurface(const VectorXd& query) const {
    if (min_.size() != query.size())
      throw std::runtime_error("Incorrect query dimension.");

    VectorXd projection(min_.size());
    for (size_t ii = 0; ii < min_.size(); ii++)
      projection(ii) = (query(ii) >= 0.0) ? max_(ii) : min_(ii);

    return projection;
  }

 private:
  // Lower and upper bounds..
  VectorXd min_, max_;
};  //\class ControlBound

}  // namespace control
}  // namespace fastrack

#endif