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

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// http://ceres-solver.org/

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// Author: sameeragarwal@google.com (Sameer Agarwal)

//

// Interface definition for sparse matrices.

#ifndef CERES_INTERNAL_SPARSE_MATRIX_H_

#define CERES_INTERNAL_SPARSE_MATRIX_H_

#include <cstdio>

#include "ceres/linear_operator.h"

#include "ceres/internal/eigen.h"

#include "ceres/types.h"

namespace ceres {

namespace internal {

// This class defines the interface for storing and manipulating

// sparse matrices. The key property that differentiates different

// sparse matrices is how they are organized in memory and how the

// information about the sparsity structure of the matrix is

// stored. This has significant implications for linear solvers

// operating on these matrices.

//

// To deal with the different kinds of layouts, we will assume that a

// sparse matrix will have a two part representation. A values array

// that will be used to store the entries of the sparse matrix and

// some sort of a layout object that tells the user the sparsity

// structure and layout of the values array. For example in case of

// the TripletSparseMatrix, this information is carried in the rows

// and cols arrays and for the BlockSparseMatrix, this information is

// carried in the CompressedRowBlockStructure object.

//

// This interface deliberately does not contain any information about

// the structure of the sparse matrix as that seems to be highly

// matrix type dependent and we are at this stage unable to come up

// with an efficient high level interface that spans multiple sparse

// matrix types.

class SparseMatrix : public LinearOperator {

 public:

  virtual ~SparseMatrix();

  // y += Ax;

  virtual void RightMultiply(const double* x, double* y) const = 0;

  // y += A'x;

  virtual void LeftMultiply(const double* x, double* y) const = 0;

  // In MATLAB notation sum(A.*A, 1)

  virtual void SquaredColumnNorm(double* x) const = 0;

  // A = A * diag(scale)

  virtual void ScaleColumns(const double* scale) = 0;

  // A = 0. A->num_nonzeros() == 0 is true after this call. The

  // sparsity pattern is preserved.

  virtual void SetZero() = 0;

  // Resize and populate dense_matrix with a dense version of the

  // sparse matrix.

  virtual void ToDenseMatrix(Matrix* dense_matrix) const = 0;

  // Write out the matrix as a sequence of (i,j,s) triplets. This

  // format is useful for loading the matrix into MATLAB/octave as a

  // sparse matrix.

  virtual void ToTextFile(FILE* file) const = 0;

  // Accessors for the values array that stores the entries of the

  // sparse matrix. The exact interpreptation of the values of this

  // array depends on the particular kind of SparseMatrix being

  // accessed.

  virtual double* mutable_values() = 0;

  virtual const double* values() const = 0;

  virtual int num_rows() const = 0;

  virtual int num_cols() const = 0;

  virtual int num_nonzeros() const = 0;

};

}  // namespace internal

}  // namespace ceres

#endif  // CERES_INTERNAL_SPARSE_MATRIX_H_