// 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/internal/eigen.h"
#include "ceres/parameter_block.h"
#include "ceres/program.h"
#include "ceres/residual_block.h"
#include "ceres/scratch_evaluate_preparer.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_
