// Ceres Solver - A fast non-linear least squares minimizer

// Copyright 2015 Google Inc. All rights reserved.

// http://ceres-solver.org/

//

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// modification, are permitted provided that the following conditions are met:

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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 const* const* jacobian_layout,

                                 int max_derivatives_per_residual_block) {

  jacobian_layout_ = jacobian_layout;

  scratch_evaluate_preparer_.Init(max_derivatives_per_residual_block);

}

// 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) {

  // If the overall jacobian is not available, use the scratch space.

  if (jacobian == NULL) {

    scratch_evaluate_preparer_.Prepare(residual_block,

                                       residual_block_index,

                                       jacobian,

                                       jacobians);

    return;

  }

  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