// Ceres Solver - A fast non-linear least squares minimizer
// Copyright 2015 Google Inc. All rights reserved.
// http://ceres-solver.org/
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// Author: richie.stebbing@gmail.com (Richard Stebbing)
//
// A jacobian writer that directly writes to dynamic compressed row sparse
// matrices.

#ifndef CERES_INTERNAL_DYNAMIC_COMPRESSED_ROW_JACOBIAN_WRITER_H_
#define CERES_INTERNAL_DYNAMIC_COMPRESSED_ROW_JACOBIAN_WRITER_H_

#include "ceres/evaluator.h"
#include "ceres/scratch_evaluate_preparer.h"

namespace ceres {
namespace internal {

class Program;
class SparseMatrix;

class DynamicCompressedRowJacobianWriter {
 public:
  DynamicCompressedRowJacobianWriter(Evaluator::Options /* ignored */,
                                     Program* program)
    : program_(program) {
  }

  // JacobianWriter interface.

  // The compressed row matrix has different layout than that assumed by
  // the cost functions. The scratch space is therefore used to store
  // the jacobians (including zeros) temporarily before only the non-zero
  // entries are copied over to the larger jacobian in `Write`.
  ScratchEvaluatePreparer* CreateEvaluatePreparers(int num_threads);

  // Return a `DynamicCompressedRowSparseMatrix` which is filled by
  // `Write`. Note that `Finalize` must be called to make the
  // `CompressedRowSparseMatrix` interface valid.
  SparseMatrix* CreateJacobian() const;

  // Write only the non-zero jacobian entries for a residual block
  // (specified by `residual_id`) into `base_jacobian`, starting at the row
  // specifed by `residual_offset`.
  //
  // This method is thread-safe over residual blocks (each `residual_id`).
  void Write(int residual_id,
             int residual_offset,
             double **jacobians,
             SparseMatrix* base_jacobian);

 private:
  Program* program_;
};

}  // namespace internal
}  // namespace ceres

#endif  // CERES_INTERNAL_DYNAMIC_COMPRESSED_ROW_JACOBIAN_WRITER_H_