// Ceres Solver - A fast non-linear least squares minimizer
// Copyright 2010, 2011, 2012 Google Inc. All rights reserved.
// http://code.google.com/p/ceres-solver/
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// Author: keir@google.com (Keir Mierle)
//
// A jacobian writer that directly writes to compressed row sparse matrices.

#ifndef CERES_INTERNAL_COMPRESSED_ROW_JACOBIAN_WRITER_H_
#define CERES_INTERNAL_COMPRESSED_ROW_JACOBIAN_WRITER_H_

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

namespace ceres {
namespace internal {

class CompressedRowSparseMatrix;
class Program;
class SparseMatrix;

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

  // `PopulateJacobianRowAndColumnBlockVectors` sets `col_blocks` and
  // `row_blocks` for a `CompressedRowSparseMatrix`, based on the parameter
  // block sizes and residual sizes respectively from the program. This is
  // useful when Solver::Options::use_block_amd = true;
  //
  // This function is static so that it is available to other jacobian
  // writers which use `CompressedRowSparseMatrix` (or derived types).
  // (Jacobian writers do not fall under any type hierarchy; they only
  // have to provide an interface as specified in program_evaluator.h).
  static void PopulateJacobianRowAndColumnBlockVectors(
      const Program* program,
      CompressedRowSparseMatrix* jacobian);

  // It is necessary to determine the order of the jacobian blocks before
  // copying them into a `CompressedRowSparseMatrix` (or derived type).
  // Just because a cost function uses parameter blocks 1 after 2 in its
  // arguments does not mean that the block 1 occurs before block 2 in the
  // column layout of the jacobian. Thus, `GetOrderedParameterBlocks`
  // determines the order by sorting the jacobian blocks by their position in
  // the state vector.
  //
  // This function is static so that it is available to other jacobian
  // writers which use `CompressedRowSparseMatrix` (or derived types).
  // (Jacobian writers do not fall under any type hierarchy; they only
  // have to provide an interface as specified in program_evaluator.h).
  static void GetOrderedParameterBlocks(
      const Program* program,
      int residual_id,
      vector<pair<int, int> >* evaluated_jacobian_blocks);

  // JacobianWriter interface.

  // Since the compressed row 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 in the Write() function.
  ScratchEvaluatePreparer* CreateEvaluatePreparers(int num_threads) {
    return ScratchEvaluatePreparer::Create(*program_, num_threads);
  }

  SparseMatrix* CreateJacobian() const;

  void Write(int residual_id,
             int residual_offset,
             double **jacobians,
             SparseMatrix* base_jacobian);

 private:
  Program* program_;
};

}  // namespace internal
}  // namespace ceres

#endif  // CERES_INTERNAL_COMPRESSED_ROW_JACOBIAN_WRITER_H_