// 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)

#include "ceres/block_random_access_diagonal_matrix.h"

#include <algorithm>

#include <set>

#include <utility>

#include <vector>

#include "Eigen/Dense"

#include "ceres/internal/port.h"

#include "ceres/internal/scoped_ptr.h"

#include "ceres/stl_util.h"

#include "ceres/triplet_sparse_matrix.h"

#include "ceres/types.h"

#include "glog/logging.h"

namespace ceres {

namespace internal {

using std::vector;

// TODO(sameeragarwal): Drop the dependence on TripletSparseMatrix.

BlockRandomAccessDiagonalMatrix::BlockRandomAccessDiagonalMatrix(

    const vector<int>& blocks)

    : blocks_(blocks) {

  // Build the row/column layout vector and count the number of scalar

  // rows/columns.

  int num_cols = 0;

  int num_nonzeros = 0;

  vector<int> block_positions;

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

    block_positions.push_back(num_cols);

    num_cols += blocks_[i];

    num_nonzeros += blocks_[i] * blocks_[i];

  }

  VLOG(1) << "Matrix Size [" << num_cols

          << "," << num_cols

          << "] " << num_nonzeros;

  tsm_.reset(new TripletSparseMatrix(num_cols, num_cols, num_nonzeros));

  tsm_->set_num_nonzeros(num_nonzeros);

  int* rows = tsm_->mutable_rows();

  int* cols = tsm_->mutable_cols();

  double* values = tsm_->mutable_values();

  int pos = 0;

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

    const int block_size = blocks_[i];

    layout_.push_back(new CellInfo(values + pos));

    const int block_begin = block_positions[i];

    for (int r = 0; r < block_size; ++r) {

      for (int c = 0; c < block_size; ++c, ++pos) {

        rows[pos] = block_begin + r;

        cols[pos] = block_begin + c;

      }

    }

  }

}

// Assume that the user does not hold any locks on any cell blocks

// when they are calling SetZero.

BlockRandomAccessDiagonalMatrix::~BlockRandomAccessDiagonalMatrix() {

  STLDeleteContainerPointers(layout_.begin(), layout_.end());

}

CellInfo* BlockRandomAccessDiagonalMatrix::GetCell(int row_block_id,

                                                   int col_block_id,

                                                   int* row,

                                                   int* col,

                                                   int* row_stride,

                                                   int* col_stride) {

  if (row_block_id != col_block_id) {

    return NULL;

  }

  const int stride = blocks_[row_block_id];

  // Each cell is stored contiguously as its own little dense matrix.

  *row = 0;

  *col = 0;

  *row_stride = stride;

  *col_stride = stride;

  return layout_[row_block_id];

}

// Assume that the user does not hold any locks on any cell blocks

// when they are calling SetZero.

void BlockRandomAccessDiagonalMatrix::SetZero() {

  if (tsm_->num_nonzeros()) {

    VectorRef(tsm_->mutable_values(),

              tsm_->num_nonzeros()).setZero();

  }

}

void BlockRandomAccessDiagonalMatrix::Invert() {

  double* values = tsm_->mutable_values();

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

    const int block_size = blocks_[i];

    MatrixRef block(values, block_size, block_size);

    block =

        block

        .selfadjointView<Eigen::Upper>()

        .llt()

        .solve(Matrix::Identity(block_size, block_size));

    values += block_size * block_size;

  }

}

void BlockRandomAccessDiagonalMatrix::RightMultiply(const double* x,

                                                    double* y) const {

  CHECK_NOTNULL(x);

  CHECK_NOTNULL(y);

  const double* values = tsm_->values();

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

    const int block_size = blocks_[i];

    ConstMatrixRef block(values, block_size, block_size);

    VectorRef(y, block_size).noalias() += block * ConstVectorRef(x, block_size);

    x += block_size;

    y += block_size;

    values += block_size * block_size;

  }

}

}  // namespace internal

}  // namespace ceres