1// Ceres Solver - A fast non-linear least squares minimizer
2// Copyright 2014 Google Inc. All rights reserved.
3// http://code.google.com/p/ceres-solver/
4//
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28//
29// Author: richie.stebbing@gmail.com (Richard Stebbing)
30//
31// A compressed row sparse matrix that provides an extended interface to
32// allow dynamic insertion of entries. This is provided for the use case
33// where the sparsity structure and number of non-zero entries is dynamic.
34// This flexibility is achieved by using an (internal) scratch space that
35// allows independent insertion of entries into each row (thread-safe).
36// Once insertion is complete, the `Finalize` method must be called to ensure
37// that the underlying `CompressedRowSparseMatrix` is consistent.
38//
39// This should only be used if you really do need a dynamic sparsity pattern.
40
41#ifndef CERES_INTERNAL_DYNAMIC_COMPRESSED_ROW_SPARSE_MATRIX_H_
42#define CERES_INTERNAL_DYNAMIC_COMPRESSED_ROW_SPARSE_MATRIX_H_
43
44#include "ceres/compressed_row_sparse_matrix.h"
45
46namespace ceres {
47namespace internal {
48
49class DynamicCompressedRowSparseMatrix : public CompressedRowSparseMatrix {
50 public:
51  // Set the number of rows and columns for the underlyig
52  // `CompressedRowSparseMatrix` and set the initial number of maximum non-zero
53  // entries. Note that following the insertion of entries, when `Finalize`
54  // is called the number of non-zeros is determined and all internal
55  // structures are adjusted as required. If you know the upper limit on the
56  // number of non-zeros, then passing this value here can prevent future
57  // memory reallocations which may improve performance. Otherwise, if no
58  // upper limit is available a value of 0 is sufficient.
59  //
60  // Typical usage of this class is to define a new instance with a given
61  // number of rows, columns and maximum number of non-zero elements
62  // (if available). Next, entries are inserted at row and column positions
63  // using `InsertEntry`. Finally, once all elements have been inserted,
64  // `Finalize` must be called to make the underlying
65  // `CompressedRowSparseMatrix` consistent.
66  DynamicCompressedRowSparseMatrix(int num_rows,
67                                   int num_cols,
68                                   int initial_max_num_nonzeros);
69
70  // Insert an entry at a given row and column position. This method is
71  // thread-safe across rows i.e. different threads can insert values
72  // simultaneously into different rows. It should be emphasised that this
73  // method always inserts a new entry and does not check for existing
74  // entries at the specified row and column position. Duplicate entries
75  // for a given row and column position will result in undefined
76  // behavior.
77  void InsertEntry(int row, int col, const double& value);
78
79  // Clear all entries for rows, starting from row index `row_start`
80  // and proceeding for `num_rows`.
81  void ClearRows(int row_start, int num_rows);
82
83  // Make the underlying internal `CompressedRowSparseMatrix` data structures
84  // consistent. Additional space for non-zero entries in the
85  // `CompressedRowSparseMatrix` can be reserved by specifying
86  // `num_additional_elements`. This is useful when it is known that rows will
87  // be appended to the `CompressedRowSparseMatrix` (e.g. appending a diagonal
88  // matrix to the jacobian) as it prevents need for future reallocation.
89  void Finalize(int num_additional_elements);
90
91 private:
92  vector<vector<int> > dynamic_cols_;
93  vector<vector<double> > dynamic_values_;
94};
95
96}  // namespace internal
97}  // namespace ceres
98
99#endif // CERES_INTERNAL_DYNAMIC_COMPRESSED_ROW_SPARSE_MATRIX_H_
100