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#ifndef CERES_INTERNAL_PARAMETER_BLOCK_ORDERING_H_
32#define CERES_INTERNAL_PARAMETER_BLOCK_ORDERING_H_
33
34#include <vector>
35#include "ceres/ordered_groups.h"
36#include "ceres/graph.h"
37#include "ceres/types.h"
38
39namespace ceres {
40namespace internal {
41
42class Program;
43class ParameterBlock;
44
45// Uses an approximate independent set ordering to order the parameter
46// blocks of a problem so that it is suitable for use with Schur
47// complement based solvers. The output variable ordering contains an
48// ordering of the parameter blocks and the return value is size of
49// the independent set or the number of e_blocks (see
50// schur_complement_solver.h for an explanation). Constant parameters
51// are added to the end.
52//
53// The ordering vector has the structure
54//
55// ordering = [independent set,
56//             complement of the independent set,
57//             fixed blocks]
58int ComputeSchurOrdering(const Program& program,
59                         vector<ParameterBlock* >* ordering);
60
61// Same as above, except that ties while computing the independent set
62// ordering are resolved in favour of the order in which the parameter
63// blocks occur in the program.
64int ComputeStableSchurOrdering(const Program& program,
65                               vector<ParameterBlock* >* ordering);
66
67// Use an approximate independent set ordering to decompose the
68// parameter blocks of a problem in a sequence of independent
69// sets. The ordering covers all the non-constant parameter blocks in
70// the program.
71void ComputeRecursiveIndependentSetOrdering(const Program& program,
72                                            ParameterBlockOrdering* ordering);
73
74// Builds a graph on the parameter blocks of a Problem, whose
75// structure reflects the sparsity structure of the Hessian. Each
76// vertex corresponds to a parameter block in the Problem except for
77// parameter blocks that are marked constant. An edge connects two
78// parameter blocks, if they co-occur in a residual block.
79Graph<ParameterBlock*>* CreateHessianGraph(const Program& program);
80
81// Iterate over each of the groups in order of their priority and fill
82// summary with their sizes.
83void OrderingToGroupSizes(const ParameterBlockOrdering* ordering,
84                          vector<int>* group_sizes);
85
86}  // namespace internal
87}  // namespace ceres
88
89#endif  // CERES_INTERNAL_PARAMETER_BLOCK_ORDERING_H_
90