// 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_