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

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

//

// For generalized bi-partite Jacobian matrices that arise in

// Structure from Motion related problems, it is sometimes useful to

// have access to the two parts of the matrix as linear operators

// themselves. This class provides that functionality.

#ifndef CERES_INTERNAL_PARTITIONED_MATRIX_VIEW_H_

#define CERES_INTERNAL_PARTITIONED_MATRIX_VIEW_H_

#include <algorithm>

#include <cstring>

#include <vector>

#include "ceres/block_structure.h"

#include "ceres/internal/eigen.h"

#include "ceres/linear_solver.h"

#include "ceres/small_blas.h"

#include "glog/logging.h"

namespace ceres {

namespace internal {

// Given generalized bi-partite matrix A = [E F], with the same block

// structure as required by the Schur complement based solver, found

// in explicit_schur_complement_solver.h, provide access to the

// matrices E and F and their outer products E'E and F'F with

// themselves.

//

// Lack of BlockStructure object will result in a crash and if the

// block structure of the matrix does not satisfy the requirements of

// the Schur complement solver it will result in unpredictable and

// wrong output.

class PartitionedMatrixViewBase {

 public:

  virtual ~PartitionedMatrixViewBase() {}

  // y += E'x

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

  // y += F'x

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

  // y += Ex

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

  // y += Fx

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

  // Create and return the block diagonal of the matrix E'E.

  virtual BlockSparseMatrix* CreateBlockDiagonalEtE() const = 0;

  // Create and return the block diagonal of the matrix F'F. Caller

  // owns the result.

  virtual BlockSparseMatrix* CreateBlockDiagonalFtF() const = 0;

  // Compute the block diagonal of the matrix E'E and store it in

  // block_diagonal. The matrix block_diagonal is expected to have a

  // BlockStructure (preferably created using

  // CreateBlockDiagonalMatrixEtE) which is has the same structure as

  // the block diagonal of E'E.

  virtual void UpdateBlockDiagonalEtE(

      BlockSparseMatrix* block_diagonal) const = 0;

  // Compute the block diagonal of the matrix F'F and store it in

  // block_diagonal. The matrix block_diagonal is expected to have a

  // BlockStructure (preferably created using

  // CreateBlockDiagonalMatrixFtF) which is has the same structure as

  // the block diagonal of F'F.

  virtual void UpdateBlockDiagonalFtF(

      BlockSparseMatrix* block_diagonal) const = 0;

  virtual int num_col_blocks_e() const = 0;

  virtual int num_col_blocks_f() const = 0;

  virtual int num_cols_e()       const = 0;

  virtual int num_cols_f()       const = 0;

  virtual int num_rows()         const = 0;

  virtual int num_cols()         const = 0;

  static PartitionedMatrixViewBase* Create(const LinearSolver::Options& options,

                                           const BlockSparseMatrix& matrix);

};

template 

          int kEBlockSize = Eigen::Dynamic,

          int kFBlockSize = Eigen::Dynamic >

class PartitionedMatrixView : public PartitionedMatrixViewBase {

 public:

  // matrix = [E F], where the matrix E contains the first

  // num_col_blocks_a column blocks.

  PartitionedMatrixView(const BlockSparseMatrix& matrix, int num_col_blocks_e);

  virtual ~PartitionedMatrixView();

  virtual void LeftMultiplyE(const double* x, double* y) const;

  virtual void LeftMultiplyF(const double* x, double* y) const;

  virtual void RightMultiplyE(const double* x, double* y) const;

  virtual void RightMultiplyF(const double* x, double* y) const;

  virtual BlockSparseMatrix* CreateBlockDiagonalEtE() const;

  virtual BlockSparseMatrix* CreateBlockDiagonalFtF() const;

  virtual void UpdateBlockDiagonalEtE(BlockSparseMatrix* block_diagonal) const;

  virtual void UpdateBlockDiagonalFtF(BlockSparseMatrix* block_diagonal) const;

  virtual int num_col_blocks_e() const { return num_col_blocks_e_;  }

  virtual int num_col_blocks_f() const { return num_col_blocks_f_;  }

  virtual int num_cols_e()       const { return num_cols_e_;        }

  virtual int num_cols_f()       const { return num_cols_f_;        }

  virtual int num_rows()         const { return matrix_.num_rows(); }

  virtual int num_cols()         const { return matrix_.num_cols(); }

 private:

  BlockSparseMatrix* CreateBlockDiagonalMatrixLayout(int start_col_block,

                                                     int end_col_block) const;

  const BlockSparseMatrix& matrix_;

  int num_row_blocks_e_;

  int num_col_blocks_e_;

  int num_col_blocks_f_;

  int num_cols_e_;

  int num_cols_f_;

};

}  // namespace internal

}  // namespace ceres

#endif  // CERES_INTERNAL_PARTITIONED_MATRIX_VIEW_H_