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// 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:
//
// * Redistributions of source code must retain the above copyright notice,
// 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"
// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
// ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
// LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
// CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
// SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
// CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
// ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
// POSSIBILITY OF SUCH DAMAGE.
//
// 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 "ceres/mutex.h"
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);
// CeresMutexLock 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(NULL) {
}
explicit CellInfo(double* ptr)
: values(ptr) {
}
double* values;
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_
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