weighted-smooth-1norm.hpp

// BSD 3-Clause License
//
// Copyright (C) 2026, Heriot-Watt University
// Copyright note valid unless otherwise stated in individual files.
// All rights reserved.

#ifndef CROCODDYL_CORE_ACTIVATIONS_WEIGHTED_SMOOTH_1NORM_HPP_
#define CROCODDYL_CORE_ACTIVATIONS_WEIGHTED_SMOOTH_1NORM_HPP_

#include "crocoddyl/core/activation-base.hpp"
#include "crocoddyl/core/fwd.hpp"

namespace crocoddyl {

template <typename _Scalar>
class ActivationModelWeightedSmooth1NormTpl
 : public ActivationModelAbstractTpl<_Scalar> {
 public:
 EIGEN_MAKE_ALIGNED_OPERATOR_NEW
 CROCODDYL_DERIVED_CAST(ActivationModelBase,
 ActivationModelWeightedSmooth1NormTpl)

 typedef _Scalar Scalar;
 typedef MathBaseTpl<Scalar> MathBase;
 typedef ActivationModelAbstractTpl<Scalar> Base;
 typedef ActivationDataAbstractTpl<Scalar> ActivationDataAbstract;
 typedef ActivationDataWeightedSmooth1NormTpl<Scalar> Data;
 typedef typename MathBase::VectorXs VectorXs;

 explicit ActivationModelWeightedSmooth1NormTpl(
 const VectorXs& weights, const Scalar delta = Scalar(1.))
 : Base(weights.size()), weights_(weights), delta_(delta) {
 check_weights(weights_);
 if (delta_ <= Scalar(0.)) {
 throw_pretty(
 "Invalid argument: delta should be a strictly positive value");
 }
 }
 virtual ~ActivationModelWeightedSmooth1NormTpl() = default;

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

 d->a = (r.array().square() + delta_ * delta_).sqrt().matrix();
 data->a_value =
 delta_ *
 (weights_.array() * r.array().square() / (d->a.array() + delta_)).sum();
 }

 virtual void calcDiff(const std::shared_ptr<ActivationDataAbstract>& data,
 const Eigen::Ref<const VectorXs>& r) override {
 if (static_cast<std::size_t>(r.size()) != nr_) {
 throw_pretty(
 "Invalid argument: " << "r has wrong dimension (it should be " +
 std::to_string(nr_) + ")");
 }
 std::shared_ptr<Data> d = std::static_pointer_cast<Data>(data);
 const VectorXs a_inv = d->a.cwiseInverse();
 data->Ar = delta_ * weights_.cwiseProduct(r).cwiseProduct(a_inv);
 data->Arr.diagonal() =
 delta_ * delta_ * delta_ *
 weights_.cwiseProduct(a_inv.cwiseProduct(a_inv).cwiseProduct(a_inv));
 }

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

 template <typename NewScalar>
 ActivationModelWeightedSmooth1NormTpl<NewScalar> cast() const {
 typedef ActivationModelWeightedSmooth1NormTpl<NewScalar> ReturnType;
 return ReturnType(weights_.template cast<NewScalar>(),
 scalar_cast<NewScalar>(delta_));
 }

 const VectorXs& get_weights() const { return weights_; }
 Scalar get_delta() const { return delta_; }

 void set_weights(const VectorXs& weights) {
 if (weights.size() != weights_.size()) {
 throw_pretty("Invalid argument: "
 << "weight vector has wrong dimension (it should be " +
 std::to_string(weights_.size()) + ")");
 }
 check_weights(weights);
 weights_ = weights;
 }

 virtual void print(std::ostream& os) const override {
 os << "ActivationModelWeightedSmooth1Norm {nr=" << nr_
 << ", delta=" << delta_ << "}";
 }

 protected:
 using Base::nr_;

 private:
 static void check_weights(const VectorXs& weights) {
 for (Eigen::Index i = 0; i < weights.size(); ++i) {
 if (weights[i] < Scalar(0.)) {
 throw_pretty(
 "Invalid argument: weights should contain nonnegative values");
 }
 }
 }

 VectorXs weights_;
 Scalar delta_;
};

template <typename _Scalar>
struct ActivationDataWeightedSmooth1NormTpl
 : public ActivationDataAbstractTpl<_Scalar> {
 EIGEN_MAKE_ALIGNED_OPERATOR_NEW

 typedef _Scalar Scalar;
 typedef ActivationDataAbstractTpl<Scalar> Base;
 typedef MathBaseTpl<Scalar> MathBase;
 typedef typename MathBase::VectorXs VectorXs;

 template <typename Activation>
 explicit ActivationDataWeightedSmooth1NormTpl(Activation* const activation)
 : Base(activation), a(VectorXs::Zero(activation->get_nr())) {}
 virtual ~ActivationDataWeightedSmooth1NormTpl() = default;

 VectorXs a;

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

} // namespace crocoddyl

CROCODDYL_DECLARE_EXTERN_TEMPLATE_CLASS(
 crocoddyl::ActivationModelWeightedSmooth1NormTpl)
CROCODDYL_DECLARE_EXTERN_TEMPLATE_STRUCT(
 crocoddyl::ActivationDataWeightedSmooth1NormTpl)

#endif // CROCODDYL_CORE_ACTIVATIONS_WEIGHTED_SMOOTH_1NORM_HPP_