QuadraticPrior.h

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//
//
/*
    Copyright (C) 2000- 2011, Hammersmith Imanet Ltd
    This file is part of STIR.

    SPDX-License-Identifier: Apache-2.0

    See STIR/LICENSE.txt for details.
*/
#ifndef __stir_recon_buildblock_QuadraticPrior_H__
#define __stir_recon_buildblock_QuadraticPrior_H__

#include "stir/RegisteredParsingObject.h"
#include "stir/recon_buildblock/PriorWithParabolicSurrogate.h"
#include "stir/Array.h"
#include "stir/DiscretisedDensity.h"
#include "stir/shared_ptr.h"
#include <string>

START_NAMESPACE_STIR

template <typename elemT>
class QuadraticPrior : public RegisteredParsingObject<QuadraticPrior<elemT>,
                                                      GeneralisedPrior<DiscretisedDensity<3, elemT>>,
                                                      PriorWithParabolicSurrogate<DiscretisedDensity<3, elemT>>>
{
private:
  typedef RegisteredParsingObject<QuadraticPrior<elemT>,
                                  GeneralisedPrior<DiscretisedDensity<3, elemT>>,
                                  PriorWithParabolicSurrogate<DiscretisedDensity<3, elemT>>>
      base_type;

public:
  static const char* const registered_name;

  QuadraticPrior();

  QuadraticPrior(const bool only_2D, float penalization_factor);

  bool parabolic_surrogate_curvature_depends_on_argument() const override { return false; }

  bool is_convex() const override;

  double compute_value(const DiscretisedDensity<3, elemT>& current_image_estimate) override;

  void compute_gradient(DiscretisedDensity<3, elemT>& prior_gradient,
                        const DiscretisedDensity<3, elemT>& current_image_estimate) override;


  void parabolic_surrogate_curvature(DiscretisedDensity<3, elemT>& parabolic_surrogate_curvature,
                                     const DiscretisedDensity<3, elemT>& current_image_estimate) override;

  void compute_Hessian(DiscretisedDensity<3, elemT>& prior_Hessian_for_single_densel,
                       const BasicCoordinate<3, int>& coords,
                       const DiscretisedDensity<3, elemT>& current_image_estimate) const override;

  void add_multiplication_with_approximate_Hessian(DiscretisedDensity<3, elemT>& output,
                                                   const DiscretisedDensity<3, elemT>& input) const override;

  void accumulate_Hessian_times_input(DiscretisedDensity<3, elemT>& output,
                                      const DiscretisedDensity<3, elemT>& current_estimate,
                                      const DiscretisedDensity<3, elemT>& input) const override;

  Array<3, float> get_weights() const;

  void set_weights(const Array<3, float>&);


  shared_ptr<const DiscretisedDensity<3, elemT>> get_kappa_sptr() const;

  void set_kappa_sptr(const shared_ptr<const DiscretisedDensity<3, elemT>>&);

  Succeeded set_up(shared_ptr<const DiscretisedDensity<3, elemT>> const& target_sptr) override;

protected:
  bool only_2D;

  std::string gradient_filename_prefix;


  mutable Array<3, float> weights;
  std::string kappa_filename;

  void check(DiscretisedDensity<3, elemT> const& current_image_estimate) const override;

  void set_defaults() override;
  void initialise_keymap() override;
  bool post_processing() override;

private:
  shared_ptr<const DiscretisedDensity<3, elemT>> kappa_ptr;


  elemT derivative_20(const elemT x_j, const elemT x_k) const;
  elemT derivative_11(const elemT x_j, const elemT x_k) const;
};

END_NAMESPACE_STIR

#endif