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:
7//
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16//
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28//
29// Author: kushalav@google.com (Avanish Kushal)
30//         sameeragarwal@google.com (Sameer Agarwal)
31//
32// Functions to manipulate visibility information from the block
33// structure of sparse matrices.
34
35#ifndef CERES_INTERNAL_VISIBILITY_H_
36#define CERES_INTERNAL_VISIBILITY_H_
37
38// This include must come before any #ifndef check on Ceres compile options.
39#include "ceres/internal/port.h"
40
41#ifndef CERES_NO_SUITESPARSE
42
43#include <set>
44#include <vector>
45#include "ceres/graph.h"
46
47namespace ceres {
48namespace internal {
49
50struct CompressedRowBlockStructure;
51
52// Given a compressed row block structure, computes the set of
53// e_blocks "visible" to each f_block. If an e_block co-occurs with an
54// f_block in a residual block, it is visible to the f_block. The
55// first num_eliminate_blocks columns blocks are e_blocks and the rest
56// f_blocks.
57//
58// In a structure from motion problem, e_blocks correspond to 3D
59// points and f_blocks correspond to cameras.
60void ComputeVisibility(const CompressedRowBlockStructure& block_structure,
61                       int num_eliminate_blocks,
62                       vector<set<int> >* visibility);
63
64// Given f_block visibility as computed by the ComputeVisibility
65// function above, construct and return a graph whose vertices are
66// f_blocks and an edge connects two vertices if they have atleast one
67// e_block in common. The weight of this edge is normalized dot
68// product between the visibility vectors of the two
69// vertices/f_blocks.
70//
71// This graph reflects the sparsity structure of reduced camera
72// matrix/Schur complement matrix obtained by eliminating the e_blocks
73// from the normal equations.
74//
75// Caller acquires ownership of the returned Graph pointer
76// (heap-allocated).
77Graph<int>* CreateSchurComplementGraph(const vector<set<int> >& visibility);
78
79}  // namespace internal
80}  // namespace ceres
81
82#endif  // CERES_NO_SUITESPARSE
83#endif  // CERES_INTERNAL_VISIBILITY_H_
84