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      1 // Ceres Solver - A fast non-linear least squares minimizer
      2 // Copyright 2010, 2011, 2012 Google Inc. All rights reserved.
      3 // http://code.google.com/p/ceres-solver/
      4 //
      5 // Redistribution and use in source and binary forms, with or without
      6 // modification, are permitted provided that the following conditions are met:
      7 //
      8 // * Redistributions of source code must retain the above copyright notice,
      9 //   this list of conditions and the following disclaimer.
     10 // * Redistributions in binary form must reproduce the above copyright notice,
     11 //   this list of conditions and the following disclaimer in the documentation
     12 //   and/or other materials provided with the distribution.
     13 // * Neither the name of Google Inc. nor the names of its contributors may be
     14 //   used to endorse or promote products derived from this software without
     15 //   specific prior written permission.
     16 //
     17 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
     18 // AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     19 // IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     20 // ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
     21 // LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
     22 // CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
     23 // SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
     24 // INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
     25 // CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
     26 // ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
     27 // POSSIBILITY OF SUCH DAMAGE.
     28 //
     29 // Author: sameeragarwal (at) google.com (Sameer Agarwal)
     30 
     31 #include "ceres/parameter_block_ordering.h"
     32 
     33 #include "ceres/graph.h"
     34 #include "ceres/graph_algorithms.h"
     35 #include "ceres/internal/scoped_ptr.h"
     36 #include "ceres/map_util.h"
     37 #include "ceres/parameter_block.h"
     38 #include "ceres/program.h"
     39 #include "ceres/residual_block.h"
     40 #include "glog/logging.h"
     41 
     42 namespace ceres {
     43 namespace internal {
     44 
     45 int ComputeStableSchurOrdering(const Program& program,
     46                          vector<ParameterBlock*>* ordering) {
     47   CHECK_NOTNULL(ordering)->clear();
     48 
     49   scoped_ptr<Graph< ParameterBlock*> > graph(CreateHessianGraph(program));
     50   const vector<ParameterBlock*>& parameter_blocks = program.parameter_blocks();
     51   const HashSet<ParameterBlock*>& vertices = graph->vertices();
     52   for (int i = 0; i < parameter_blocks.size(); ++i) {
     53     if (vertices.count(parameter_blocks[i]) > 0) {
     54       ordering->push_back(parameter_blocks[i]);
     55     }
     56   }
     57 
     58   int independent_set_size = StableIndependentSetOrdering(*graph, ordering);
     59 
     60   // Add the excluded blocks to back of the ordering vector.
     61   for (int i = 0; i < parameter_blocks.size(); ++i) {
     62     ParameterBlock* parameter_block = parameter_blocks[i];
     63     if (parameter_block->IsConstant()) {
     64       ordering->push_back(parameter_block);
     65     }
     66   }
     67 
     68   return independent_set_size;
     69 }
     70 
     71 int ComputeSchurOrdering(const Program& program,
     72                          vector<ParameterBlock*>* ordering) {
     73   CHECK_NOTNULL(ordering)->clear();
     74 
     75   scoped_ptr<Graph< ParameterBlock*> > graph(CreateHessianGraph(program));
     76   int independent_set_size = IndependentSetOrdering(*graph, ordering);
     77   const vector<ParameterBlock*>& parameter_blocks = program.parameter_blocks();
     78 
     79   // Add the excluded blocks to back of the ordering vector.
     80   for (int i = 0; i < parameter_blocks.size(); ++i) {
     81     ParameterBlock* parameter_block = parameter_blocks[i];
     82     if (parameter_block->IsConstant()) {
     83       ordering->push_back(parameter_block);
     84     }
     85   }
     86 
     87   return independent_set_size;
     88 }
     89 
     90 void ComputeRecursiveIndependentSetOrdering(const Program& program,
     91                                             ParameterBlockOrdering* ordering) {
     92   CHECK_NOTNULL(ordering)->Clear();
     93   const vector<ParameterBlock*> parameter_blocks = program.parameter_blocks();
     94   scoped_ptr<Graph< ParameterBlock*> > graph(CreateHessianGraph(program));
     95 
     96   int num_covered = 0;
     97   int round = 0;
     98   while (num_covered < parameter_blocks.size()) {
     99     vector<ParameterBlock*> independent_set_ordering;
    100     const int independent_set_size =
    101         IndependentSetOrdering(*graph, &independent_set_ordering);
    102     for (int i = 0; i < independent_set_size; ++i) {
    103       ParameterBlock* parameter_block = independent_set_ordering[i];
    104       ordering->AddElementToGroup(parameter_block->mutable_user_state(), round);
    105       graph->RemoveVertex(parameter_block);
    106     }
    107     num_covered += independent_set_size;
    108     ++round;
    109   }
    110 }
    111 
    112 Graph<ParameterBlock*>*
    113 CreateHessianGraph(const Program& program) {
    114   Graph<ParameterBlock*>* graph = CHECK_NOTNULL(new Graph<ParameterBlock*>);
    115   const vector<ParameterBlock*>& parameter_blocks = program.parameter_blocks();
    116   for (int i = 0; i < parameter_blocks.size(); ++i) {
    117     ParameterBlock* parameter_block = parameter_blocks[i];
    118     if (!parameter_block->IsConstant()) {
    119       graph->AddVertex(parameter_block);
    120     }
    121   }
    122 
    123   const vector<ResidualBlock*>& residual_blocks = program.residual_blocks();
    124   for (int i = 0; i < residual_blocks.size(); ++i) {
    125     const ResidualBlock* residual_block = residual_blocks[i];
    126     const int num_parameter_blocks = residual_block->NumParameterBlocks();
    127     ParameterBlock* const* parameter_blocks =
    128         residual_block->parameter_blocks();
    129     for (int j = 0; j < num_parameter_blocks; ++j) {
    130       if (parameter_blocks[j]->IsConstant()) {
    131         continue;
    132       }
    133 
    134       for (int k = j + 1; k < num_parameter_blocks; ++k) {
    135         if (parameter_blocks[k]->IsConstant()) {
    136           continue;
    137         }
    138 
    139         graph->AddEdge(parameter_blocks[j], parameter_blocks[k]);
    140       }
    141     }
    142   }
    143 
    144   return graph;
    145 }
    146 
    147 }  // namespace internal
    148 }  // namespace ceres
    149