OptionalJacobian.h

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/* ----------------------------------------------------------------------------

 * GTSAM Copyright 2010, Georgia Tech Research Corporation,
 * Atlanta, Georgia 30332-0415
 * All Rights Reserved
 * Authors: Frank Dellaert, et al. (see THANKS for the full author list)

 * See LICENSE for the license information

 * -------------------------------------------------------------------------- */

#pragma once
#include <gtsam/config.h>      // Configuration from CMake
#include <Eigen/Dense>

#ifndef OPTIONALJACOBIAN_NOBOOST
#include <boost/optional.hpp>
#endif

namespace gtsam {

template<int Rows, int Cols>
class OptionalJacobian {

public:

  typedef Eigen::Matrix<double, Rows, Cols> Jacobian;

private:

  Eigen::Map<Jacobian> map_; 

  // Trick from http://eigen.tuxfamily.org/dox/group__TutorialMapClass.html
  // uses "placement new" to make map_ usurp the memory of the fixed size matrix
  void usurp(double* data) {
    new (&map_) Eigen::Map<Jacobian>(data);
  }

  // Private and very dangerous constructor straight from memory
  OptionalJacobian(double* data) : map_(nullptr) {
    if (data) usurp(data);
  }

  template<int M, int N>
  friend class OptionalJacobian;

public:

  OptionalJacobian() :
      map_(nullptr) {
  }

  OptionalJacobian(Jacobian& fixed) :
      map_(nullptr) {
    usurp(fixed.data());
  }

  OptionalJacobian(Jacobian* fixedPtr) :
      map_(nullptr) {
    if (fixedPtr)
      usurp(fixedPtr->data());
  }

  OptionalJacobian(Eigen::MatrixXd& dynamic) :
      map_(nullptr) {
    dynamic.resize(Rows, Cols); // no malloc if correct size
    usurp(dynamic.data());
  }

#ifndef OPTIONALJACOBIAN_NOBOOST

  OptionalJacobian(boost::none_t /*none*/) :
      map_(nullptr) {
  }

  OptionalJacobian(const boost::optional<Eigen::MatrixXd&> optional) :
      map_(nullptr) {
    if (optional) {
      optional->resize(Rows, Cols);
      usurp(optional->data());
    }
  }

#endif

  //  template <typename Derived, bool InnerPanel>
  //  OptionalJacobian(Eigen::Block<Derived,Rows,Cols,InnerPanel> block) : map_(nullptr) { ?? }

  operator bool() const {
    return map_.data() != nullptr;
  }

  Eigen::Map<Jacobian>& operator*() {
    return map_;
  }

  Eigen::Map<Jacobian>* operator->() {
    return &map_;
  }

  //  template <int M, int N>
  //  OptionalJacobian<M, N> block(int startRow, int startCol) {
  //    if (*this)
  //      OptionalJacobian<M, N>(map_.block<M, N>(startRow, startCol));
  //    else
  //      return OptionalJacobian<M, N>();
  //  }

  template <int N>
  OptionalJacobian<Rows, N> cols(int startCol) {
    if (*this)
      return OptionalJacobian<Rows, N>(&map_(0,startCol));
    else
      return OptionalJacobian<Rows, N>();
  }

};

// The pure dynamic specialization of this is needed to support
// variable-sized types. Note that this is designed to work like the
// boost optional scheme from GTSAM 3.
template<>
class OptionalJacobian<Eigen::Dynamic, Eigen::Dynamic> {

public:

  typedef Eigen::MatrixXd Jacobian;

private:

  Jacobian* pointer_; 

public:

  OptionalJacobian() :
    pointer_(nullptr) {
  }

  OptionalJacobian(Jacobian* pointer) : pointer_(pointer) {}

  OptionalJacobian(Jacobian& dynamic) : pointer_(&dynamic) {}

#ifndef OPTIONALJACOBIAN_NOBOOST

  OptionalJacobian(boost::none_t /*none*/) :
    pointer_(nullptr) {
  }

  OptionalJacobian(const boost::optional<Eigen::MatrixXd&> optional) :
      pointer_(nullptr) {
    if (optional) pointer_ = &(*optional);
  }

#endif

  operator bool() const {
    return pointer_!=nullptr;
  }

  Jacobian& operator*() {
    return *pointer_;
  }

  Jacobian* operator->(){ return pointer_; }
};

// forward declare
template <typename T> struct traits;

template <class T, class A>
struct MakeJacobian {
  typedef Eigen::Matrix<double, traits<T>::dimension, traits<A>::dimension> type;
};

template<class T, class A>
struct MakeOptionalJacobian {
  typedef OptionalJacobian<traits<T>::dimension,
      traits<A>::dimension> type;
};

} // namespace gtsam