// 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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// modification, are permitted provided that the following conditions are met:
//
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//   this list of conditions and the following disclaimer.
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// Author: keir@google.com (Keir Mierle)

#include "ceres/block_evaluate_preparer.h"

#include <vector>
#include "ceres/block_sparse_matrix.h"
#include "ceres/casts.h"
#include "ceres/parameter_block.h"
#include "ceres/residual_block.h"
#include "ceres/sparse_matrix.h"

namespace ceres {
namespace internal {

void BlockEvaluatePreparer::Init(int** jacobian_layout) {
  jacobian_layout_ = jacobian_layout;
}

// Point the jacobian blocks directly into the block sparse matrix.
void BlockEvaluatePreparer::Prepare(const ResidualBlock* residual_block,
                                    int residual_block_index,
                                    SparseMatrix* jacobian,
                                    double** jacobians) const {
  CHECK(jacobian != NULL);
  double* jacobian_values =
      down_cast<BlockSparseMatrix*>(jacobian)->mutable_values();

  const int* jacobian_block_offset = jacobian_layout_[residual_block_index];
  const int num_parameter_blocks = residual_block->NumParameterBlocks();
  for (int j = 0; j < num_parameter_blocks; ++j) {
    if (!residual_block->parameter_blocks()[j]->IsConstant()) {
      jacobians[j] = jacobian_values + *jacobian_block_offset;

      // The jacobian_block_offset can't be indexed with 'j' since the code
      // that creates the layout strips out any blocks for inactive
      // parameters. Instead, bump the pointer for active parameters only.
      jacobian_block_offset++;
    } else {
      jacobians[j] = NULL;
    }
  }
}

}  // namespace internal
}  // namespace ceres