// Ceres Solver - A fast non-linear least squares minimizer

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// Author: richie.stebbing@gmail.com (Richard Stebbing)

//

// A compressed row sparse matrix that provides an extended interface to

// allow dynamic insertion of entries. This is provided for the use case

// where the sparsity structure and number of non-zero entries is dynamic.

// This flexibility is achieved by using an (internal) scratch space that

// allows independent insertion of entries into each row (thread-safe).

// Once insertion is complete, the `Finalize` method must be called to ensure

// that the underlying `CompressedRowSparseMatrix` is consistent.

//

// This should only be used if you really do need a dynamic sparsity pattern.

#ifndef CERES_INTERNAL_DYNAMIC_COMPRESSED_ROW_SPARSE_MATRIX_H_

#define CERES_INTERNAL_DYNAMIC_COMPRESSED_ROW_SPARSE_MATRIX_H_

#include <vector>

#include "ceres/compressed_row_sparse_matrix.h"

namespace ceres {

namespace internal {

class DynamicCompressedRowSparseMatrix : public CompressedRowSparseMatrix {

 public:

  // Set the number of rows and columns for the underlyig

  // `CompressedRowSparseMatrix` and set the initial number of maximum non-zero

  // entries. Note that following the insertion of entries, when `Finalize`

  // is called the number of non-zeros is determined and all internal

  // structures are adjusted as required. If you know the upper limit on the

  // number of non-zeros, then passing this value here can prevent future

  // memory reallocations which may improve performance. Otherwise, if no

  // upper limit is available a value of 0 is sufficient.

  //

  // Typical usage of this class is to define a new instance with a given

  // number of rows, columns and maximum number of non-zero elements

  // (if available). Next, entries are inserted at row and column positions

  // using `InsertEntry`. Finally, once all elements have been inserted,

  // `Finalize` must be called to make the underlying

  // `CompressedRowSparseMatrix` consistent.

  DynamicCompressedRowSparseMatrix(int num_rows,

                                   int num_cols,

                                   int initial_max_num_nonzeros);

  // Insert an entry at a given row and column position. This method is

  // thread-safe across rows i.e. different threads can insert values

  // simultaneously into different rows. It should be emphasised that this

  // method always inserts a new entry and does not check for existing

  // entries at the specified row and column position. Duplicate entries

  // for a given row and column position will result in undefined

  // behavior.

  void InsertEntry(int row, int col, const double& value);

  // Clear all entries for rows, starting from row index `row_start`

  // and proceeding for `num_rows`.

  void ClearRows(int row_start, int num_rows);

  // Make the underlying internal `CompressedRowSparseMatrix` data structures

  // consistent. Additional space for non-zero entries in the

  // `CompressedRowSparseMatrix` can be reserved by specifying

  // `num_additional_elements`. This is useful when it is known that rows will

  // be appended to the `CompressedRowSparseMatrix` (e.g. appending a diagonal

  // matrix to the jacobian) as it prevents need for future reallocation.

  void Finalize(int num_additional_elements);

 private:

  std::vector<std::vector<int> > dynamic_cols_;

  std::vector<std::vector<double> > dynamic_values_;

};

}  // namespace internal

}  // namespace ceres

#endif  // CERES_INTERNAL_DYNAMIC_COMPRESSED_ROW_SPARSE_MATRIX_H_