Line data    Source code

       1             : #pragma once
       2             : 
       3             : #include "LineSearchMethod.h"
       4             : #include "LeastSquares.h"
       5             : 
       6             : namespace elsa
       7             : {
       8             :     /**
       9             :      * @brief Steepest Descent Step for Least Squares
      10             :      *
      11             :      * SteepestDescentStepLS returns the step size @f$\alpha@f$ that minimizes the objective
      12             :      * function along the descent direction using the analytical solution:
      13             :      *
      14             :      * @f[
      15             :      * \alpha = \frac{b^T A d_i - x_i^T A^T A d_i}{d_i^TA^TAd_i}
      16             :      * @f]
      17             :      *
      18             :      * where @f$A: \mathbb{R}^{n \times m} is the system matrix@f$,
      19             :      * @f$ x_i: \mathbb{R}^n is the current solution guess@f$
      20             :      * @f$b: \mathbb{R}^m data to use in the linear residual@f$, and
      21             :      * @f$ d_i: \mathbb{R}^n is the search direction @f$
      22             :      *
      23             :      * @author
      24             :      * - Said Alghabra - initial code
      25             :      *
      26             :      * @tparam data_t data type for the domain and range of the problem, defaulting to real_t
      27             :      */
      28             :     template <typename data_t = real_t>
      29             :     class SteepestDescentStepLS : public LineSearchMethod<data_t>
      30             :     {
      31             :     public:
      32             :         SteepestDescentStepLS(const LeastSquares<data_t>& problem);
      33          20 :         ~SteepestDescentStepLS() override = default;
      34             : 
      35             :         /// make copy constructor deletion explicit
      36             :         SteepestDescentStepLS(const SteepestDescentStepLS<data_t>&) = delete;
      37             : 
      38             :         data_t solve(DataContainer<data_t> xi, DataContainer<data_t> di) override;
      39             : 
      40             :         /// implement the polymorphic comparison operation
      41             :         bool isEqual(const LineSearchMethod<data_t>& other) const override;
      42             : 
      43             :     private:
      44             :         // the system matrix
      45             :         std::unique_ptr<LinearOperator<data_t>> _A{};
      46             : 
      47             :         // the projections vector (sinogram)
      48             :         DataContainer<data_t> _b{};
      49             : 
      50             :         /// implement the polymorphic clone operation
      51             :         SteepestDescentStepLS<data_t>* cloneImpl() const override;
      52             :     };
      53             : } // namespace elsa