2norm-barrier.hpp

// BSD 3-Clause License
//
// Copyright (C) 2021, LAAS-CNRS, Airbus, University of Edinburgh
// Copyright note valid unless otherwise stated in individual files.
// All rights reserved.

#ifndef CROCODDYL_CORE_ACTIVATIONS_2NORM_BARRIER_HPP_
#define CROCODDYL_CORE_ACTIVATIONS_2NORM_BARRIER_HPP_

#include <stdexcept>
#include <pinocchio/utils/static-if.hpp>
#include "crocoddyl/core/fwd.hpp"
#include "crocoddyl/core/activation-base.hpp"
#include "crocoddyl/core/utils/exception.hpp"

namespace crocoddyl {

template <typename _Scalar>
class ActivationModel2NormBarrierTpl : public ActivationModelAbstractTpl<_Scalar> {
 public:
  EIGEN_MAKE_ALIGNED_OPERATOR_NEW

  typedef _Scalar Scalar;
  typedef MathBaseTpl<Scalar> MathBase;
  typedef ActivationModelAbstractTpl<Scalar> Base;
  typedef ActivationDataAbstractTpl<Scalar> ActivationDataAbstract;
  typedef ActivationData2NormBarrierTpl<Scalar> Data;
  typedef typename MathBase::VectorXs VectorXs;

  explicit ActivationModel2NormBarrierTpl(const std::size_t nr, const Scalar alpha = Scalar(0.1),
                                          const bool true_hessian = false)
      : Base(nr), alpha_(alpha), true_hessian_(true_hessian) {
    if (alpha < Scalar(0.)) {
      throw_pretty("Invalid argument: "
                   << "alpha should be a positive value");
    }
  };
  virtual ~ActivationModel2NormBarrierTpl(){};

  virtual void calc(const boost::shared_ptr<ActivationDataAbstract>& data, const Eigen::Ref<const VectorXs>& r) {
    if (static_cast<std::size_t>(r.size()) != nr_) {
      throw_pretty("Invalid argument: "
                   << "r has wrong dimension (it should be " + std::to_string(nr_) + ")");
    }
    boost::shared_ptr<Data> d = boost::static_pointer_cast<Data>(data);

    d->d = r.norm();
    if (d->d < alpha_) {
      data->a_value = Scalar(0.5) * (d->d - alpha_) * (d->d - alpha_);
    } else {
      data->a_value = Scalar(0.0);
    }
  };

  virtual void calcDiff(const boost::shared_ptr<ActivationDataAbstract>& data, const Eigen::Ref<const VectorXs>& r) {
    if (static_cast<std::size_t>(r.size()) != nr_) {
      throw_pretty("Invalid argument: "
                   << "r has wrong dimension (it should be " + std::to_string(nr_) + ")");
    }
    boost::shared_ptr<Data> d = boost::static_pointer_cast<Data>(data);

    if (d->d < alpha_) {
      data->Ar = (d->d - alpha_) / d->d * r;
      if (true_hessian_) {
        data->Arr.diagonal() = alpha_ * r.array().square() / std::pow(d->d, 3);  // True Hessian
        data->Arr.diagonal().array() += (d->d - alpha_) / d->d;
      } else {
        data->Arr.diagonal() = r.array().square() / std::pow(d->d, 2);  // GN Hessian approximation
      }
    } else {
      data->Ar.setZero();
      data->Arr.setZero();
    }
  };

  virtual boost::shared_ptr<ActivationDataAbstract> createData() {
    return boost::allocate_shared<Data>(Eigen::aligned_allocator<Data>(), this);
  };

  const Scalar& get_alpha() const { return alpha_; };
  void set_alpha(const Scalar& alpha) { alpha_ = alpha; };

  virtual void print(std::ostream& os) const {
    os << "ActivationModel2NormBarrier {nr=" << nr_ << ", alpha=" << alpha_ << ", hessian=" << true_hessian_ << "}";
  }

 protected:
  using Base::nr_;     
  Scalar alpha_;       
  bool true_hessian_;  
};

template <typename _Scalar>
struct ActivationData2NormBarrierTpl : public ActivationDataAbstractTpl<_Scalar> {
  EIGEN_MAKE_ALIGNED_OPERATOR_NEW

  typedef _Scalar Scalar;
  typedef ActivationDataAbstractTpl<Scalar> Base;

  template <typename Activation>
  explicit ActivationData2NormBarrierTpl(Activation* const activation) : Base(activation), d(Scalar(0)) {}

  Scalar d;  

  using Base::a_value;
  using Base::Ar;
  using Base::Arr;
};

}  // namespace crocoddyl

#endif  // CROCODDYL_CORE_ACTIVATIONS_2NORM_BARRIER_HPP_