// Ceres Solver - A fast non-linear least squares minimizer

// Copyright 2015 Google Inc. All rights reserved.

// http://ceres-solver.org/

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// Author: sameeragarwal@google.com (Sameer Agarwal)

#ifndef CERES_INTERNAL_LINE_SEARCH_DIRECTION_H_

#define CERES_INTERNAL_LINE_SEARCH_DIRECTION_H_

#include "ceres/internal/eigen.h"

#include "ceres/line_search_minimizer.h"

#include "ceres/types.h"

namespace ceres {

namespace internal {

class LineSearchDirection {

 public:

  struct Options {

    Options()

        : num_parameters(0),

          type(LBFGS),

          nonlinear_conjugate_gradient_type(FLETCHER_REEVES),

          function_tolerance(1e-12),

          max_lbfgs_rank(20),

          use_approximate_eigenvalue_bfgs_scaling(true) {

    }

    int num_parameters;

    LineSearchDirectionType type;

    NonlinearConjugateGradientType nonlinear_conjugate_gradient_type;

    double function_tolerance;

    int max_lbfgs_rank;

    bool use_approximate_eigenvalue_bfgs_scaling;

  };

  static LineSearchDirection* Create(const Options& options);

  virtual ~LineSearchDirection() {}

  virtual bool NextDirection(const LineSearchMinimizer::State& previous,

                             const LineSearchMinimizer::State& current,

                             Vector* search_direction) = 0;

};

}  // namespace internal

}  // namespace ceres

#endif  // CERES_INTERNAL_LINE_SEARCH_DIRECTION_H_