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

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

//

// A jacobian writer that writes to dense Eigen matrices.

#ifndef CERES_INTERNAL_DENSE_JACOBIAN_WRITER_H_

#define CERES_INTERNAL_DENSE_JACOBIAN_WRITER_H_

#include "ceres/casts.h"

#include "ceres/dense_sparse_matrix.h"

#include "ceres/parameter_block.h"

#include "ceres/program.h"

#include "ceres/residual_block.h"

#include "ceres/scratch_evaluate_preparer.h"

#include "ceres/internal/eigen.h"

namespace ceres {

namespace internal {

class DenseJacobianWriter {

 public:

  DenseJacobianWriter(Evaluator::Options /* ignored */,

                      Program* program)

    : program_(program) {

  }

  // JacobianWriter interface.

  // Since the dense matrix has different layout than that assumed by the cost

  // functions, use scratch space to store the jacobians temporarily then copy

  // them over to the larger jacobian later.

  ScratchEvaluatePreparer* CreateEvaluatePreparers(int num_threads) {

    return ScratchEvaluatePreparer::Create(*program_, num_threads);

  }

  SparseMatrix* CreateJacobian() const {

    return new DenseSparseMatrix(program_->NumResiduals(),

                                 program_->NumEffectiveParameters(),

                                 true);

  }

  void Write(int residual_id,

             int residual_offset,

             double **jacobians,

             SparseMatrix* jacobian) {

    DenseSparseMatrix* dense_jacobian = down_cast<DenseSparseMatrix*>(jacobian);

    const ResidualBlock* residual_block =

        program_->residual_blocks()[residual_id];

    int num_parameter_blocks = residual_block->NumParameterBlocks();

    int num_residuals = residual_block->NumResiduals();

    // Now copy the jacobians for each parameter into the dense jacobian matrix.

    for (int j = 0; j < num_parameter_blocks; ++j) {

      ParameterBlock* parameter_block = residual_block->parameter_blocks()[j];

      // If the parameter block is fixed, then there is nothing to do.

      if (parameter_block->IsConstant()) {

        continue;

      }

      const int parameter_block_size = parameter_block->LocalSize();

      ConstMatrixRef parameter_jacobian(jacobians[j],

                                        num_residuals,

                                        parameter_block_size);

      dense_jacobian->mutable_matrix().block(

          residual_offset,

          parameter_block->delta_offset(),

          num_residuals,

          parameter_block_size) = parameter_jacobian;

    }

  }

 private:

  Program* program_;

};

}  // namespace internal

}  // namespace ceres

#endif  // CERES_INTERNAL_DENSE_JACOBIAN_WRITER_H_