single_player_dynamical_system.h

/*
 * Copyright (c) 2019, The Regents of the University of California (Regents).
 * All rights reserved.
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 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met:
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 *    1. Redistributions of source code must retain the above copyright
 *       notice, this list of conditions and the following disclaimer.
 *
 *    2. Redistributions in binary form must reproduce the above
 *       copyright notice, this list of conditions and the following
 *       disclaimer in the documentation and/or other materials provided
 *       with the distribution.
 *
 *    3. Neither the name of the copyright holder nor the names of its
 *       contributors may be used to endorse or promote products derived
 *       from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS AS IS
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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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 )
 */

///////////////////////////////////////////////////////////////////////////////
//
// Base class for all single-player dynamical systems. Supports (discrete-time)
// linearization.
//
///////////////////////////////////////////////////////////////////////////////

#ifndef ILQGAMES_DYNAMICS_SINGLE_PLAYER_DYNAMICAL_SYSTEM_H
#define ILQGAMES_DYNAMICS_SINGLE_PLAYER_DYNAMICAL_SYSTEM_H

#include <ilqgames/utils/types.h>

namespace ilqgames {

class SinglePlayerDynamicalSystem {
 public:
  virtual ~SinglePlayerDynamicalSystem() {}

  // Compute time derivative of state.
  virtual VectorXf Evaluate(Time t, const VectorXf& x,
                            const VectorXf& u) const = 0;

  // Compute a discrete-time Jacobian linearization.
  // NOTE: assumes A, B already initialized (to I, 0 respectively) for speed.
  // NOTE: this function signature violates Google style guide return by
  // pointer convention intentionally, in order to comply with Eigen standard:
  // https://eigen.tuxfamily.org/dox/TopicFunctionTakingEigenTypes.html
  virtual void Linearize(Time t, const VectorXf& x, const VectorXf& u,
                         Eigen::Ref<MatrixXf> A,
                         Eigen::Ref<MatrixXf> B) const = 0;

  // Distance metric on the state space. By default, just the *squared* 2-norm.
  virtual float DistanceBetween(const VectorXf& x0, const VectorXf& x1) const {
    return (x0 - x1).squaredNorm();
  }

  // Getters.
  Dimension XDim() const { return xdim_; }
  Dimension UDim() const { return udim_; }
  virtual std::vector<Dimension> PositionDimensions() const = 0;

 protected:
  SinglePlayerDynamicalSystem(Dimension xdim, Dimension udim)
      : xdim_(xdim), udim_(udim) {}

  // Dimensions.
  const Dimension xdim_;
  const Dimension udim_;
};  //\class SinglePlayerDynamicalSystem

}  // namespace ilqgames

#endif