1 // Ceres Solver - A fast non-linear least squares minimizer
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29 // Author: sameeragarwal@google.com (Sameer Agarwal)
31 // Limited memory positive definite approximation to the inverse
32 // Hessian, using the LBFGS algorithm
34 #ifndef CERES_INTERNAL_LOW_RANK_INVERSE_HESSIAN_H_
35 #define CERES_INTERNAL_LOW_RANK_INVERSE_HESSIAN_H_
39 #include "ceres/internal/eigen.h"
40 #include "ceres/linear_operator.h"
45 // LowRankInverseHessian is a positive definite approximation to the
46 // Hessian using the limited memory variant of the
47 // Broyden-Fletcher-Goldfarb-Shanno (BFGS)secant formula for
48 // approximating the Hessian.
50 // Other update rules like the Davidon-Fletcher-Powell (DFP) are
51 // possible, but the BFGS rule is considered the best performing one.
53 // The limited memory variant was developed by Nocedal and further
54 // enhanced with scaling rule by Byrd, Nocedal and Schanbel.
56 // Nocedal, J. (1980). "Updating Quasi-Newton Matrices with Limited
57 // Storage". Mathematics of Computation 35 (151): 773–782.
59 // Byrd, R. H.; Nocedal, J.; Schnabel, R. B. (1994).
60 // "Representations of Quasi-Newton Matrices and their use in
61 // Limited Memory Methods". Mathematical Programming 63 (4):
62 class LowRankInverseHessian : public LinearOperator {
64 // num_parameters is the row/column size of the Hessian.
65 // max_num_corrections is the rank of the Hessian approximation.
66 // use_approximate_eigenvalue_scaling controls whether the initial
67 // inverse Hessian used during Right/LeftMultiply() is scaled by
68 // the approximate eigenvalue of the true inverse Hessian at the
69 // current operating point.
70 // The approximation uses:
71 // 2 * max_num_corrections * num_parameters + max_num_corrections
73 LowRankInverseHessian(int num_parameters,
74 int max_num_corrections,
75 bool use_approximate_eigenvalue_scaling);
76 virtual ~LowRankInverseHessian() {}
78 // Update the low rank approximation. delta_x is the change in the
79 // domain of Hessian, and delta_gradient is the change in the
80 // gradient. The update copies the delta_x and delta_gradient
81 // vectors, and gets rid of the oldest delta_x and delta_gradient
82 // vectors if the number of corrections is already equal to
83 // max_num_corrections.
84 bool Update(const Vector& delta_x, const Vector& delta_gradient);
86 // LinearOperator interface
87 virtual void RightMultiply(const double* x, double* y) const;
88 virtual void LeftMultiply(const double* x, double* y) const {
91 virtual int num_rows() const { return num_parameters_; }
92 virtual int num_cols() const { return num_parameters_; }
95 const int num_parameters_;
96 const int max_num_corrections_;
97 const bool use_approximate_eigenvalue_scaling_;
98 double approximate_eigenvalue_scale_;
99 ColMajorMatrix delta_x_history_;
100 ColMajorMatrix delta_gradient_history_;
101 Vector delta_x_dot_delta_gradient_;
102 std::list<int> indices_;
105 } // namespace internal
108 #endif // CERES_INTERNAL_LOW_RANK_INVERSE_HESSIAN_H_