internal/ceres/scratch_evaluate_preparer.h

// Ceres Solver - A fast non-linear least squares minimizer
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// Author: keir@google.com (Keir Mierle)
//
// A scratch evaluate preparer provides temporary storage for the jacobians that
// are created when running user-provided cost functions. The evaluator takes
// care to avoid evaluating the jacobian for fixed parameters.

#ifndef CERES_INTERNAL_SCRATCH_EVALUATE_PREPARER_H_
#define CERES_INTERNAL_SCRATCH_EVALUATE_PREPARER_H_

#include <memory>

namespace ceres {
namespace internal {

class Program;
class ResidualBlock;
class SparseMatrix;

class ScratchEvaluatePreparer {
 public:
  // Create num_threads ScratchEvaluatePreparers.
  static ScratchEvaluatePreparer* Create(const Program &program,
                                         int num_threads);

  // EvaluatePreparer interface
  void Init(int max_derivatives_per_residual_block);
  void Prepare(const ResidualBlock* residual_block,
               int residual_block_index,
               SparseMatrix* jacobian,
               double** jacobians);

 private:
  // Scratch space for the jacobians; each jacobian is packed one after another.
  // There is enough scratch to hold all the jacobians for the largest residual.
  std::unique_ptr<double[]> jacobian_scratch_;
};

}  // namespace internal
}  // namespace ceres

#endif  // CERES_INTERNAL_SCRATCH_EVALUATE_PREPARER_H_