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//
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6// modification, are permitted provided that the following conditions are met:
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16//
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28//
29// Author: sameeragarwal@google.com (Sameer Agarwal)
30
31#include "ceres/schur_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
42namespace ceres {
43namespace internal {
44
45int ComputeSchurOrdering(const Program& program,
46                         vector<ParameterBlock*>* ordering) {
47  CHECK_NOTNULL(ordering)->clear();
48
49  scoped_ptr<Graph< ParameterBlock*> > graph(
50      CHECK_NOTNULL(CreateHessianGraph(program)));
51  int independent_set_size = IndependentSetOrdering(*graph, ordering);
52  const vector<ParameterBlock*>& parameter_blocks = program.parameter_blocks();
53
54  // Add the excluded blocks to back of the ordering vector.
55  for (int i = 0; i < parameter_blocks.size(); ++i) {
56    ParameterBlock* parameter_block = parameter_blocks[i];
57    if (parameter_block->IsConstant()) {
58      ordering->push_back(parameter_block);
59    }
60  }
61
62  return independent_set_size;
63}
64
65Graph<ParameterBlock*>*
66CreateHessianGraph(const Program& program) {
67  Graph<ParameterBlock*>* graph = new Graph<ParameterBlock*>;
68  const vector<ParameterBlock*>& parameter_blocks = program.parameter_blocks();
69  for (int i = 0; i < parameter_blocks.size(); ++i) {
70    ParameterBlock* parameter_block = parameter_blocks[i];
71    if (!parameter_block->IsConstant()) {
72      graph->AddVertex(parameter_block);
73    }
74  }
75
76  const vector<ResidualBlock*>& residual_blocks = program.residual_blocks();
77  for (int i = 0; i < residual_blocks.size(); ++i) {
78    const ResidualBlock* residual_block = residual_blocks[i];
79    const int num_parameter_blocks = residual_block->NumParameterBlocks();
80    ParameterBlock* const* parameter_blocks =
81        residual_block->parameter_blocks();
82    for (int j = 0; j < num_parameter_blocks; ++j) {
83      if (parameter_blocks[j]->IsConstant()) {
84        continue;
85      }
86
87      for (int k = j + 1; k < num_parameter_blocks; ++k) {
88        if (parameter_blocks[k]->IsConstant()) {
89          continue;
90        }
91
92        graph->AddEdge(parameter_blocks[j], parameter_blocks[k]);
93      }
94    }
95  }
96
97  return graph;
98}
99
100}  // namespace internal
101}  // namespace ceres
102