| // Ceres Solver - A fast non-linear least squares minimizer |
| // Copyright 2015 Google Inc. All rights reserved. |
| // http://ceres-solver.org/ |
| // |
| // Redistribution and use in source and binary forms, with or without |
| // modification, are permitted provided that the following conditions are met: |
| // |
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| // this list of conditions and the following disclaimer. |
| // * Redistributions in binary form must reproduce the above copyright notice, |
| // this list of conditions and the following disclaimer in the documentation |
| // and/or other materials provided with the distribution. |
| // * Neither the name of Google Inc. nor the names of its contributors may be |
| // used to endorse or promote products derived from this software without |
| // specific prior written permission. |
| // |
| // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" |
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| // |
| // Author: sameeragarwal@google.com (Sameer Agarwal) |
| // |
| // Interface for matrices that allow block based random access. |
| |
| #ifndef CERES_INTERNAL_BLOCK_RANDOM_ACCESS_MATRIX_H_ |
| #define CERES_INTERNAL_BLOCK_RANDOM_ACCESS_MATRIX_H_ |
| |
| #include <mutex> |
| |
| namespace ceres { |
| namespace internal { |
| |
| // A matrix implementing the BlockRandomAccessMatrix interface is a |
| // matrix whose rows and columns are divided into blocks. For example |
| // the matrix A: |
| // |
| // 3 4 5 |
| // A = 5 [c_11 c_12 c_13] |
| // 4 [c_21 c_22 c_23] |
| // |
| // has row blocks of size 5 and 4, and column blocks of size 3, 4 and |
| // 5. It has six cells corresponding to the six row-column block |
| // combinations. |
| // |
| // BlockRandomAccessMatrix objects provide access to cells c_ij using |
| // the GetCell method. when a cell is present, GetCell will return a |
| // CellInfo object containing a pointer to an array which contains the |
| // cell as a submatrix and a mutex that guards this submatrix. If the |
| // user is accessing the matrix concurrently, it is his responsibility |
| // to use the mutex to exclude other writers from writing to the cell |
| // concurrently. |
| // |
| // There is no requirement that all cells be present, i.e. the matrix |
| // itself can be block sparse. When a cell is not present, the GetCell |
| // method will return a NULL pointer. |
| // |
| // There is no requirement about how the cells are stored beyond that |
| // form a dense submatrix of a larger dense matrix. Like everywhere |
| // else in Ceres, RowMajor storage assumed. |
| // |
| // Example usage: |
| // |
| // BlockRandomAccessMatrix* A = new BlockRandomAccessMatrixSubClass(...) |
| // |
| // int row, col, row_stride, col_stride; |
| // CellInfo* cell = A->GetCell(row_block_id, col_block_id, |
| // &row, &col, |
| // &row_stride, &col_stride); |
| // |
| // if (cell != NULL) { |
| // MatrixRef m(cell->values, row_stride, col_stride); |
| // std::lock_guard<std::mutex> l(&cell->m); |
| // m.block(row, col, row_block_size, col_block_size) = ... |
| // } |
| |
| // Structure to carry a pointer to the array containing a cell and the |
| // mutex guarding it. |
| struct CellInfo { |
| CellInfo() : values(nullptr) {} |
| explicit CellInfo(double* values) : values(values) {} |
| |
| double* values; |
| std::mutex m; |
| }; |
| |
| class BlockRandomAccessMatrix { |
| public: |
| virtual ~BlockRandomAccessMatrix(); |
| |
| // If the cell (row_block_id, col_block_id) is present, then return |
| // a CellInfo with a pointer to the dense matrix containing it, |
| // otherwise return NULL. The dense matrix containing this cell has |
| // size row_stride, col_stride and the cell is located at position |
| // (row, col) within this matrix. |
| // |
| // The size of the cell is row_block_size x col_block_size is |
| // assumed known to the caller. row_block_size less than or equal to |
| // row_stride and col_block_size is upper bounded by col_stride. |
| virtual CellInfo* GetCell(int row_block_id, |
| int col_block_id, |
| int* row, |
| int* col, |
| int* row_stride, |
| int* col_stride) = 0; |
| |
| // Zero out the values of the array. The structure of the matrix |
| // (size and sparsity) is preserved. |
| virtual void SetZero() = 0; |
| |
| // Number of scalar rows and columns in the matrix, i.e the sum of |
| // all row blocks and column block sizes respectively. |
| virtual int num_rows() const = 0; |
| virtual int num_cols() const = 0; |
| }; |
| |
| } // namespace internal |
| } // namespace ceres |
| |
| #endif // CERES_INTERNAL_BLOCK_RANDOM_ACCESS_MATRIX_H_ |