1 // Ceres Solver - A fast non-linear least squares minimizer
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29 // Author: sameeragarwal@google.com (Sameer Agarwal)
30 
31 #ifndef CERES_INTERNAL_BLOCK_RANDOM_ACCESS_SPARSE_MATRIX_H_
32 #define CERES_INTERNAL_BLOCK_RANDOM_ACCESS_SPARSE_MATRIX_H_
33 
34 #include <cstdint>
35 #include <memory>
36 #include <set>
37 #include <unordered_map>
38 #include <utility>
39 #include <vector>
40 
41 #include "ceres/block_random_access_matrix.h"
42 #include "ceres/internal/port.h"
43 #include "ceres/small_blas.h"
44 #include "ceres/triplet_sparse_matrix.h"
45 #include "ceres/types.h"
46 
47 namespace ceres {
48 namespace internal {
49 
50 // A thread safe square block sparse implementation of
51 // BlockRandomAccessMatrix. Internally a TripletSparseMatrix is used
52 // for doing the actual storage. This class augments this matrix with
53 // an unordered_map that allows random read/write access.
54 class CERES_EXPORT_INTERNAL BlockRandomAccessSparseMatrix
55     : public BlockRandomAccessMatrix {
56  public:
57   // blocks is an array of block sizes. block_pairs is a set of
58   // <row_block_id, col_block_id> pairs to identify the non-zero cells
59   // of this matrix.
60   BlockRandomAccessSparseMatrix(
61       const std::vector<int>& blocks,
62       const std::set<std::pair<int, int>>& block_pairs);
63   BlockRandomAccessSparseMatrix(const BlockRandomAccessSparseMatrix&) = delete;
64   void operator=(const BlockRandomAccessSparseMatrix&) = delete;
65 
66   // The destructor is not thread safe. It assumes that no one is
67   // modifying any cells when the matrix is being destroyed.
68   virtual ~BlockRandomAccessSparseMatrix();
69 
70   // BlockRandomAccessMatrix Interface.
71   CellInfo* GetCell(int row_block_id,
72                     int col_block_id,
73                     int* row,
74                     int* col,
75                     int* row_stride,
76                     int* col_stride) final;
77 
78   // This is not a thread safe method, it assumes that no cell is
79   // locked.
80   void SetZero() final;
81 
82   // Assume that the matrix is symmetric and only one half of the
83   // matrix is stored.
84   //
85   // y += S * x
86   void SymmetricRightMultiply(const double* x, double* y) const;
87 
88   // Since the matrix is square, num_rows() == num_cols().
num_rows()89   int num_rows() const final { return tsm_->num_rows(); }
num_cols()90   int num_cols() const final { return tsm_->num_cols(); }
91 
92   // Access to the underlying matrix object.
matrix()93   const TripletSparseMatrix* matrix() const { return tsm_.get(); }
mutable_matrix()94   TripletSparseMatrix* mutable_matrix() { return tsm_.get(); }
95 
96  private:
IntPairToLong(int row,int col)97   int64_t IntPairToLong(int row, int col) const {
98     return row * kMaxRowBlocks + col;
99   }
100 
LongToIntPair(int64_t index,int * row,int * col)101   void LongToIntPair(int64_t index, int* row, int* col) const {
102     *row = index / kMaxRowBlocks;
103     *col = index % kMaxRowBlocks;
104   }
105 
106   const int64_t kMaxRowBlocks;
107 
108   // row/column block sizes.
109   const std::vector<int> blocks_;
110   std::vector<int> block_positions_;
111 
112   // A mapping from <row_block_id, col_block_id> to the position in
113   // the values array of tsm_ where the block is stored.
114   typedef std::unordered_map<long int, CellInfo*> LayoutType;
115   LayoutType layout_;
116 
117   // In order traversal of contents of the matrix. This allows us to
118   // implement a matrix-vector which is 20% faster than using the
119   // iterator in the Layout object instead.
120   std::vector<std::pair<std::pair<int, int>, double*>> cell_values_;
121   // The underlying matrix object which actually stores the cells.
122   std::unique_ptr<TripletSparseMatrix> tsm_;
123 
124   friend class BlockRandomAccessSparseMatrixTest;
125 };
126 
127 }  // namespace internal
128 }  // namespace ceres
129 
130 #endif  // CERES_INTERNAL_BLOCK_RANDOM_ACCESS_SPARSE_MATRIX_H_
131