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+// Ceres Solver - A fast non-linear least squares minimizer
+// Copyright 2014 Google Inc. All rights reserved.
+// http://code.google.com/p/ceres-solver/
+//
+// 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: 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 "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:
+  vector<vector<int> > dynamic_cols_;
+  vector<vector<double> > dynamic_values_;
+};
+
+}  // namespace internal
+}  // namespace ceres
+
+#endif // CERES_INTERNAL_DYNAMIC_COMPRESSED_ROW_SPARSE_MATRIX_H_