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

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// Author: keir@google.com (Keir Mierle)

#include "ceres/block_jacobi_preconditioner.h"

#include "ceres/block_sparse_matrix.h"

#include "ceres/block_structure.h"

#include "ceres/block_random_access_diagonal_matrix.h"

#include "ceres/casts.h"

#include "ceres/integral_types.h"

#include "ceres/internal/eigen.h"

namespace ceres {

namespace internal {

BlockJacobiPreconditioner::BlockJacobiPreconditioner(

    const BlockSparseMatrix& A) {

  const CompressedRowBlockStructure* bs = A.block_structure();

  std::vector<int> blocks(bs->cols.size());

  for (int i = 0; i < blocks.size(); ++i) {

    blocks[i] = bs->cols[i].size;

  }

  m_.reset(new BlockRandomAccessDiagonalMatrix(blocks));

}

BlockJacobiPreconditioner::~BlockJacobiPreconditioner() {}

bool BlockJacobiPreconditioner::UpdateImpl(const BlockSparseMatrix& A,

                                           const double* D) {

  const CompressedRowBlockStructure* bs = A.block_structure();

  const double* values = A.values();

  m_->SetZero();

  for (int i = 0; i < bs->rows.size(); ++i) {

    const int row_block_size = bs->rows[i].block.size;

    const std::vector<Cell>& cells = bs->rows[i].cells;

    for (int j = 0; j < cells.size(); ++j) {

      const int block_id = cells[j].block_id;

      const int col_block_size = bs->cols[block_id].size;

      int r, c, row_stride, col_stride;

      CellInfo* cell_info = m_->GetCell(block_id, block_id,

                                        &r, &c,

                                        &row_stride, &col_stride);

      MatrixRef m(cell_info->values, row_stride, col_stride);

      ConstMatrixRef b(values + cells[j].position,

                       row_block_size,

                       col_block_size);

      m.block(r, c, col_block_size, col_block_size) += b.transpose() * b;

    }

  }

  if (D != NULL) {

    // Add the diagonal.

    int position = 0;

    for (int i = 0; i < bs->cols.size(); ++i) {

      const int block_size = bs->cols[i].size;

      int r, c, row_stride, col_stride;

      CellInfo* cell_info = m_->GetCell(i, i,

                                        &r, &c,

                                        &row_stride, &col_stride);

      MatrixRef m(cell_info->values, row_stride, col_stride);

      m.block(r, c, block_size, block_size).diagonal() +=

          ConstVectorRef(D + position, block_size).array().square().matrix();

      position += block_size;

    }

  }

  m_->Invert();

  return true;

}

void BlockJacobiPreconditioner::RightMultiply(const double* x,

                                              double* y) const {

  m_->RightMultiply(x, y);

}

}  // namespace internal

}  // namespace ceres