text: // 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:
  //
  // * Redistributions of source code must retain the above copyright notice,
  //   this list of conditions and the following disclaimer.
  // * Redistributions in binary form must reproduce the above copyright notice,
  //   this list of conditions and the following disclaimer in the documentation
  //   and/or other materials provided with the distribution.
  // * Neither the name of Google Inc. nor the names of its contributors may be
  //   used to endorse or promote products derived from this software without
  //   specific prior written permission.
  //
  // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
  // AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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  // ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
  // LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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  // SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
  // INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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  // ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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  //
  // Author: keir@google.com (Keir Mierle)
  
  #include "ceres/compressed_row_jacobian_writer.h"
  
  #include <iterator>
  #include <utility>
  #include <vector>
  
  #include "ceres/casts.h"
  #include "ceres/compressed_row_sparse_matrix.h"
  #include "ceres/parameter_block.h"
  #include "ceres/program.h"
  #include "ceres/residual_block.h"
  #include "ceres/scratch_evaluate_preparer.h"
  
  namespace ceres {
  namespace internal {
  
  using std::make_pair;
  using std::pair;
  using std::vector;
  using std::adjacent_find;
  
  void CompressedRowJacobianWriter::PopulateJacobianRowAndColumnBlockVectors(
      const Program* program, CompressedRowSparseMatrix* jacobian) {
    const vector<ParameterBlock*>& parameter_blocks =
        program->parameter_blocks();
    vector<int>& col_blocks = *(jacobian->mutable_col_blocks());
    col_blocks.resize(parameter_blocks.size());
    for (int i = 0; i < parameter_blocks.size(); ++i) {
      col_blocks[i] = parameter_blocks[i]->LocalSize();
    }
  
    const vector<ResidualBlock*>& residual_blocks =
        program->residual_blocks();
    vector<int>& row_blocks = *(jacobian->mutable_row_blocks());
    row_blocks.resize(residual_blocks.size());
    for (int i = 0; i < residual_blocks.size(); ++i) {
      row_blocks[i] = residual_blocks[i]->NumResiduals();
    }
  }
  
  void CompressedRowJacobianWriter::GetOrderedParameterBlocks(
        const Program* program,
        int residual_id,
        vector<pair<int, int> >* evaluated_jacobian_blocks) {
    const ResidualBlock* residual_block =
        program->residual_blocks()[residual_id];
    const int num_parameter_blocks = residual_block->NumParameterBlocks();
  
    for (int j = 0; j < num_parameter_blocks; ++j) {
      const ParameterBlock* parameter_block =
          residual_block->parameter_blocks()[j];
      if (!parameter_block->IsConstant()) {
        evaluated_jacobian_blocks->push_back(
            make_pair(parameter_block->index(), j));
      }
    }
    sort(evaluated_jacobian_blocks->begin(), evaluated_jacobian_blocks->end());
  }
  
  SparseMatrix* CompressedRowJacobianWriter::CreateJacobian() const {
    const vector<ResidualBlock*>& residual_blocks =
        program_->residual_blocks();
  
    int total_num_residuals = program_->NumResiduals();
    int total_num_effective_parameters = program_->NumEffectiveParameters();
  
    // Count the number of jacobian nonzeros.
    int num_jacobian_nonzeros = 0;
    for (int i = 0; i < residual_blocks.size(); ++i) {
      ResidualBlock* residual_block = residual_blocks[i];
      const int num_residuals = residual_block->NumResiduals();
      const int num_parameter_blocks = residual_block->NumParameterBlocks();
      for (int j = 0; j < num_parameter_blocks; ++j) {
        ParameterBlock* parameter_block = residual_block->parameter_blocks()[j];
        if (!parameter_block->IsConstant()) {
          num_jacobian_nonzeros += num_residuals * parameter_block->LocalSize();
        }
      }
    }
  
    // Allocate storage for the jacobian with some extra space at the end.
    // Allocate more space than needed to store the jacobian so that when the LM
    // algorithm adds the diagonal, no reallocation is necessary. This reduces
    // peak memory usage significantly.
    CompressedRowSparseMatrix* jacobian =
        new CompressedRowSparseMatrix(
            total_num_residuals,
            total_num_effective_parameters,
            num_jacobian_nonzeros + total_num_effective_parameters);
  
    // At this stage, the CompressedRowSparseMatrix is an invalid state. But this
    // seems to be the only way to construct it without doing a memory copy.
    int* rows = jacobian->mutable_rows();
    int* cols = jacobian->mutable_cols();
  
    // Initialize crsb rows and cols.
    std::vector<int>& crsb_rows = *jacobian->mutable_crsb_rows();
    std::vector<int>& crsb_cols = *jacobian->mutable_crsb_cols();
    crsb_rows.resize(residual_blocks.size() + 1);
    crsb_rows[0] = 0;
  
    int row_pos = 0;
    rows[0] = 0;
    for (int i = 0; i < residual_blocks.size(); ++i) {
      const ResidualBlock* residual_block = residual_blocks[i];
      const int num_parameter_blocks = residual_block->NumParameterBlocks();
  
      // Count the number of derivatives for a row of this residual block and
      // build a list of active parameter block indices.
      int num_derivatives = 0;
      vector<int> parameter_indices;
      for (int j = 0; j < num_parameter_blocks; ++j) {
        ParameterBlock* parameter_block = residual_block->parameter_blocks()[j];
        if (!parameter_block->IsConstant()) {
          parameter_indices.push_back(parameter_block->index());
          num_derivatives += parameter_block->LocalSize();
        }
      }
  
      // Sort the parameters by their position in the state vector.
      sort(parameter_indices.begin(), parameter_indices.end());
      if (adjacent_find(parameter_indices.begin(), parameter_indices.end()) !=
          parameter_indices.end()) {
        std::string parameter_block_description;
        for (int j = 0; j < num_parameter_blocks; ++j) {
          ParameterBlock* parameter_block = residual_block->parameter_blocks()[j];
          parameter_block_description +=
              parameter_block->ToString() + "\n";
        }
        LOG(FATAL) << "Ceres internal error: "
                   << "Duplicate parameter blocks detected in a cost function. "
                   << "This should never happen. Please report this to "
                   << "the Ceres developers.\n"
                   << "Residual Block: " << residual_block->ToString() << "\n"
                   << "Parameter Blocks: " << parameter_block_description;
      }
  
      // Populate crsb rows and cols.
      crsb_rows[i + 1] = crsb_rows[i] + parameter_indices.size();
      std::copy(parameter_indices.begin(), parameter_indices.end(),
                std::back_inserter(crsb_cols));
  
      // Update the row indices.
      const int num_residuals = residual_block->NumResiduals();
      for (int j = 0; j < num_residuals; ++j) {
        rows[row_pos + j + 1] = rows[row_pos + j] + num_derivatives;
      }
  
      // Iterate over parameter blocks in the order which they occur in the
      // parameter vector. This code mirrors that in Write(), where jacobian
      // values are updated.
      int col_pos = 0;
      for (int j = 0; j < parameter_indices.size(); ++j) {
        ParameterBlock* parameter_block =
            program_->parameter_blocks()[parameter_indices[j]];
        const int parameter_block_size = parameter_block->LocalSize();
  
        for (int r = 0; r < num_residuals; ++r) {
          // This is the position in the values array of the jacobian where this
          // row of the jacobian block should go.
          const int column_block_begin = rows[row_pos + r] + col_pos;
  
          for (int c = 0; c < parameter_block_size; ++c) {
            cols[column_block_begin + c] = parameter_block->delta_offset() + c;
          }
        }
        col_pos += parameter_block_size;
      }
      row_pos += num_residuals;
    }
    CHECK_EQ(num_jacobian_nonzeros, rows[total_num_residuals]);
  
    PopulateJacobianRowAndColumnBlockVectors(program_, jacobian);
  
    return jacobian;
  }
  
  void CompressedRowJacobianWriter::Write(int residual_id,
                                          int residual_offset,
                                          double **jacobians,
                                          SparseMatrix* base_jacobian) {
    CompressedRowSparseMatrix* jacobian =
        down_cast<CompressedRowSparseMatrix*>(base_jacobian);
  
    double* jacobian_values = jacobian->mutable_values();
    const int* jacobian_rows = jacobian->rows();
  
    const ResidualBlock* residual_block =
        program_->residual_blocks()[residual_id];
    const int num_residuals = residual_block->NumResiduals();
  
    vector<pair<int, int> > evaluated_jacobian_blocks;
    GetOrderedParameterBlocks(program_, residual_id, &evaluated_jacobian_blocks);
  
    // Where in the current row does the jacobian for a parameter block begin.
    int col_pos = 0;
  
    // Iterate over the jacobian blocks in increasing order of their
    // positions in the reduced parameter vector.
    for (int i = 0; i < evaluated_jacobian_blocks.size(); ++i) {
      const ParameterBlock* parameter_block =
          program_->parameter_blocks()[evaluated_jacobian_blocks[i].first];
      const int argument = evaluated_jacobian_blocks[i].second;
      const int parameter_block_size = parameter_block->LocalSize();
  
      // Copy one row of the jacobian block at a time.
      for (int r = 0; r < num_residuals; ++r) {
        // Position of the r^th row of the current jacobian block.
        const double* block_row_begin =
            jacobians[argument] + r * parameter_block_size;
  
        // Position in the values array of the jacobian where this
        // row of the jacobian block should go.
        double* column_block_begin =
            jacobian_values + jacobian_rows[residual_offset + r] + col_pos;
  
        std::copy(block_row_begin,
                  block_row_begin + parameter_block_size,
                  column_block_begin);
      }
      col_pos += parameter_block_size;
    }
  }
  
  }  // namespace internal
  }  // namespace ceres
  