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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)
+
+#ifndef CERES_INTERNAL_COMPRESSED_ROW_SPARSE_MATRIX_H_
+#define CERES_INTERNAL_COMPRESSED_ROW_SPARSE_MATRIX_H_
+
+#include <vector>
+#include "ceres/internal/port.h"
+#include "ceres/sparse_matrix.h"
+#include "ceres/types.h"
+#include "glog/logging.h"
+
+namespace ceres {
+
+struct CRSMatrix;
+
+namespace internal {
+
+class TripletSparseMatrix;
+
+class CompressedRowSparseMatrix : public SparseMatrix {
+ public:
+  enum StorageType {
+    UNSYMMETRIC,
+    // Matrix is assumed to be symmetric but only the lower triangular
+    // part of the matrix is stored.
+    LOWER_TRIANGULAR,
+    // Matrix is assumed to be symmetric but only the upper triangular
+    // part of the matrix is stored.
+    UPPER_TRIANGULAR
+  };
+
+  // Create a matrix with the same content as the TripletSparseMatrix
+  // input. We assume that input does not have any repeated
+  // entries.
+  //
+  // The storage type of the matrix is set to UNSYMMETRIC.
+  //
+  // Caller owns the result.
+  static CompressedRowSparseMatrix* FromTripletSparseMatrix(
+      const TripletSparseMatrix& input);
+
+  // Create a matrix with the same content as the TripletSparseMatrix
+  // input transposed. We assume that input does not have any repeated
+  // entries.
+  //
+  // The storage type of the matrix is set to UNSYMMETRIC.
+  //
+  // Caller owns the result.
+  static CompressedRowSparseMatrix* FromTripletSparseMatrixTransposed(
+      const TripletSparseMatrix& input);
+
+  // Use this constructor only if you know what you are doing. This
+  // creates a "blank" matrix with the appropriate amount of memory
+  // allocated. However, the object itself is in an inconsistent state
+  // as the rows and cols matrices do not match the values of
+  // num_rows, num_cols and max_num_nonzeros.
+  //
+  // The use case for this constructor is that when the user knows the
+  // size of the matrix to begin with and wants to update the layout
+  // manually, instead of going via the indirect route of first
+  // constructing a TripletSparseMatrix, which leads to more than
+  // double the peak memory usage.
+  //
+  // The storage type is set to UNSYMMETRIC.
+  CompressedRowSparseMatrix(int num_rows, int num_cols, int max_num_nonzeros);
+
+  // Build a square sparse diagonal matrix with num_rows rows and
+  // columns. The diagonal m(i,i) = diagonal(i);
+  //
+  // The storage type is set to UNSYMMETRIC
+  CompressedRowSparseMatrix(const double* diagonal, int num_rows);
+
+  // SparseMatrix interface.
+  virtual ~CompressedRowSparseMatrix();
+  virtual void SetZero();
+  virtual void RightMultiply(const double* x, double* y) const;
+  virtual void LeftMultiply(const double* x, double* y) const;
+  virtual void SquaredColumnNorm(double* x) const;
+  virtual void ScaleColumns(const double* scale);
+  virtual void ToDenseMatrix(Matrix* dense_matrix) const;
+  virtual void ToTextFile(FILE* file) const;
+  virtual int num_rows() const { return num_rows_; }
+  virtual int num_cols() const { return num_cols_; }
+  virtual int num_nonzeros() const { return rows_[num_rows_]; }
+  virtual const double* values() const { return &values_[0]; }
+  virtual double* mutable_values() { return &values_[0]; }
+
+  // Delete the bottom delta_rows.
+  // num_rows -= delta_rows
+  void DeleteRows(int delta_rows);
+
+  // Append the contents of m to the bottom of this matrix. m must
+  // have the same number of columns as this matrix.
+  void AppendRows(const CompressedRowSparseMatrix& m);
+
+  void ToCRSMatrix(CRSMatrix* matrix) const;
+
+  CompressedRowSparseMatrix* Transpose() const;
+
+  // Destructive array resizing method.
+  void SetMaxNumNonZeros(int num_nonzeros);
+
+  // Non-destructive array resizing method.
+  void set_num_rows(const int num_rows) { num_rows_ = num_rows; }
+  void set_num_cols(const int num_cols) { num_cols_ = num_cols; }
+
+  // Low level access methods that expose the structure of the matrix.
+  const int* cols() const { return &cols_[0]; }
+  int* mutable_cols() { return &cols_[0]; }
+
+  const int* rows() const { return &rows_[0]; }
+  int* mutable_rows() { return &rows_[0]; }
+
+  const StorageType storage_type() const { return storage_type_; }
+  void set_storage_type(const StorageType storage_type) {
+    storage_type_ = storage_type;
+  }
+
+  const std::vector<int>& row_blocks() const { return row_blocks_; }
+  std::vector<int>* mutable_row_blocks() { return &row_blocks_; }
+
+  const std::vector<int>& col_blocks() const { return col_blocks_; }
+  std::vector<int>* mutable_col_blocks() { return &col_blocks_; }
+
+  // Create a block diagonal CompressedRowSparseMatrix with the given
+  // block structure. The individual blocks are assumed to be laid out
+  // contiguously in the diagonal array, one block at a time.
+  //
+  // Caller owns the result.
+  static CompressedRowSparseMatrix* CreateBlockDiagonalMatrix(
+      const double* diagonal, const std::vector<int>& blocks);
+
+  // Options struct to control the generation of random block sparse
+  // matrices in compressed row sparse format.
+  //
+  // The random matrix generation proceeds as follows.
+  //
+  // First the row and column block structure is determined by
+  // generating random row and column block sizes that lie within the
+  // given bounds.
+  //
+  // Then we walk the block structure of the resulting matrix, and with
+  // probability block_density detemine whether they are structurally
+  // zero or not. If the answer is no, then we generate entries for the
+  // block which are distributed normally.
+  struct RandomMatrixOptions {
+    // Type of matrix to create.
+    //
+    // If storage_type is UPPER_TRIANGULAR (LOWER_TRIANGULAR), then
+    // create a square symmetric matrix with just the upper triangular
+    // (lower triangular) part. In this case, num_col_blocks,
+    // min_col_block_size and max_col_block_size will be ignored and
+    // assumed to be equal to the corresponding row settings.
+    StorageType storage_type = UNSYMMETRIC;
+
+    int num_row_blocks = 0;
+    int min_row_block_size = 0;
+    int max_row_block_size = 0;
+    int num_col_blocks = 0;
+    int min_col_block_size = 0;
+    int max_col_block_size = 0;
+
+    // 0 < block_density <= 1 is the probability of a block being
+    // present in the matrix. A given random matrix will not have
+    // precisely this density.
+    double block_density = 0.0;
+  };
+
+  // Create a random CompressedRowSparseMatrix whose entries are
+  // normally distributed and whose structure is determined by
+  // RandomMatrixOptions.
+  //
+  // Caller owns the result.
+  static CompressedRowSparseMatrix* CreateRandomMatrix(
+      RandomMatrixOptions options);
+
+ private:
+  static CompressedRowSparseMatrix* FromTripletSparseMatrix(
+      const TripletSparseMatrix& input, bool transpose);
+
+  int num_rows_;
+  int num_cols_;
+  std::vector<int> rows_;
+  std::vector<int> cols_;
+  std::vector<double> values_;
+  StorageType storage_type_;
+
+  // If the matrix has an underlying block structure, then it can also
+  // carry with it row and column block sizes. This is auxilliary and
+  // optional information for use by algorithms operating on the
+  // matrix. The class itself does not make use of this information in
+  // any way.
+  std::vector<int> row_blocks_;
+  std::vector<int> col_blocks_;
+};
+
+}  // namespace internal
+}  // namespace ceres
+
+#endif  // CERES_INTERNAL_COMPRESSED_ROW_SPARSE_MATRIX_H_