Line data    Source code

       1             : #pragma once
       2             : 
       3             : #include <optional>
       4             : 
       5             : #include "DataContainer.h"
       6             : #include "StrongTypes.h"
       7             : 
       8             : namespace elsa
       9             : {
      10             :     /// @brief Proximal operator of the indicator functions for box and
      11             :     /// non-negativity sets. The proximal operator is the projection of onto
      12             :     /// the given set.
      13             :     ///
      14             :     /// Given the set \f$P\f$ of elements \f$a \leq x \leq b\f$, the proximal operator
      15             :     /// for the indicator function:
      16             :     /// \f[
      17             :     /// f(x) =
      18             :     /// \begin{cases}
      19             :     ///     0      & \text{if } a \leq x \leq b \text{ everywhere}, \\ \infty & \text{else}
      20             :     /// \end{cases}
      21             :     /// \f]
      22             :     /// is given by:
      23             :     /// \f[
      24             :     /// f(x) =
      25             :     /// \begin{cases}
      26             :     ///     a & \text{if } x < a, \\ x & \text{if } a \leq x \leq b, \\ b & \text{if } x > b
      27             :     /// \end{cases}
      28             :     /// \f]
      29             :     /// The proximal operator is independent for each dimension, and hence,
      30             :     /// can be computed coefficient wise.
      31             :     ///
      32             :     /// Note: the proximal operator is independent of the step length
      33             :     ///
      34             :     /// @see IndicatorBox IndicatorNonNegativity
      35             :     template <class data_t>
      36             :     class ProximalBoxConstraint
      37             :     {
      38             :     public:
      39             :         /// defaulted default constructor
      40           4 :         ProximalBoxConstraint() = default;
      41             : 
      42             :         /// defaulted copy constructor
      43             :         ProximalBoxConstraint(const ProximalBoxConstraint<data_t>&) = default;
      44             : 
      45             :         /// defaulted copy assignment operator
      46             :         ProximalBoxConstraint& operator=(const ProximalBoxConstraint<data_t>&) = default;
      47             : 
      48             :         /// defaulted move constructor
      49             :         ProximalBoxConstraint(ProximalBoxConstraint<data_t>&&) noexcept = default;
      50             : 
      51             :         /// defaulted move assignment operator
      52             :         ProximalBoxConstraint& operator=(ProximalBoxConstraint<data_t>&&) noexcept = default;
      53             : 
      54             :         /// defaulted deconstructor
      55             :         ~ProximalBoxConstraint() = default;
      56             : 
      57             :         /// Construct proximal operator with only a lower bound
      58             :         explicit ProximalBoxConstraint(data_t lower);
      59             : 
      60             :         /// Construct proximal operator with a lower and upper bound
      61             :         ProximalBoxConstraint(data_t lower, data_t upper);
      62             : 
      63             :         /// Apply proximal operator to the given vector
      64             :         DataContainer<data_t> apply(const DataContainer<data_t>& v, SelfType_t<data_t> t) const;
      65             : 
      66             :         /// Apply proximal operator to the given vector, by projection the
      67             :         /// vector v onto the given set
      68             :         void apply(const DataContainer<data_t>& v, SelfType_t<data_t> t,
      69             :                    DataContainer<data_t>& prox) const;
      70             : 
      71             :         template <class T>
      72             :         friend bool operator==(const ProximalBoxConstraint<T>&, const ProximalBoxConstraint<T>&);
      73             : 
      74             :         template <class T>
      75             :         friend bool operator!=(const ProximalBoxConstraint<T>&, const ProximalBoxConstraint<T>&);
      76             : 
      77             :     private:
      78             :         std::optional<data_t> lower_ = {};
      79             :         std::optional<data_t> upper_ = {};
      80             :     };
      81             : } // namespace elsa