Squashed 'third_party/ceres/' content from commit e51e9b4
Change-Id: I763587619d57e594d3fa158dc3a7fe0b89a1743b
git-subtree-dir: third_party/ceres
git-subtree-split: e51e9b46f6ca88ab8b2266d0e362771db6d98067
diff --git a/internal/ceres/visibility.cc b/internal/ceres/visibility.cc
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+// Ceres Solver - A fast non-linear least squares minimizer
+// Copyright 2015 Google Inc. All rights reserved.
+// http://ceres-solver.org/
+//
+// Redistribution and use in source and binary forms, with or without
+// 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
+// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+// ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
+// LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+// CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+// SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+// CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+// ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+// POSSIBILITY OF SUCH DAMAGE.
+//
+// Author: kushalav@google.com (Avanish Kushal)
+
+#include "ceres/visibility.h"
+
+#include <cmath>
+#include <ctime>
+#include <algorithm>
+#include <set>
+#include <vector>
+#include <unordered_map>
+#include <utility>
+#include "ceres/block_structure.h"
+#include "ceres/graph.h"
+#include "ceres/pair_hash.h"
+#include "glog/logging.h"
+
+namespace ceres {
+namespace internal {
+
+using std::make_pair;
+using std::max;
+using std::pair;
+using std::set;
+using std::vector;
+
+void ComputeVisibility(const CompressedRowBlockStructure& block_structure,
+ const int num_eliminate_blocks,
+ vector<set<int>>* visibility) {
+ CHECK(visibility != nullptr);
+
+ // Clear the visibility vector and resize it to hold a
+ // vector for each camera.
+ visibility->resize(0);
+ visibility->resize(block_structure.cols.size() - num_eliminate_blocks);
+
+ for (int i = 0; i < block_structure.rows.size(); ++i) {
+ const vector<Cell>& cells = block_structure.rows[i].cells;
+ int block_id = cells[0].block_id;
+ // If the first block is not an e_block, then skip this row block.
+ if (block_id >= num_eliminate_blocks) {
+ continue;
+ }
+
+ for (int j = 1; j < cells.size(); ++j) {
+ int camera_block_id = cells[j].block_id - num_eliminate_blocks;
+ DCHECK_GE(camera_block_id, 0);
+ DCHECK_LT(camera_block_id, visibility->size());
+ (*visibility)[camera_block_id].insert(block_id);
+ }
+ }
+}
+
+WeightedGraph<int>* CreateSchurComplementGraph(
+ const vector<set<int>>& visibility) {
+ const time_t start_time = time(NULL);
+ // Compute the number of e_blocks/point blocks. Since the visibility
+ // set for each e_block/camera contains the set of e_blocks/points
+ // visible to it, we find the maximum across all visibility sets.
+ int num_points = 0;
+ for (int i = 0; i < visibility.size(); i++) {
+ if (visibility[i].size() > 0) {
+ num_points = max(num_points, (*visibility[i].rbegin()) + 1);
+ }
+ }
+
+ // Invert the visibility. The input is a camera->point mapping,
+ // which tells us which points are visible in which
+ // cameras. However, to compute the sparsity structure of the Schur
+ // Complement efficiently, its better to have the point->camera
+ // mapping.
+ vector<set<int>> inverse_visibility(num_points);
+ for (int i = 0; i < visibility.size(); i++) {
+ const set<int>& visibility_set = visibility[i];
+ for (const int v : visibility_set) {
+ inverse_visibility[v].insert(i);
+ }
+ }
+
+ // Map from camera pairs to number of points visible to both cameras
+ // in the pair.
+ std::unordered_map<pair<int, int>, int, pair_hash> camera_pairs;
+
+ // Count the number of points visible to each camera/f_block pair.
+ for (const auto& inverse_visibility_set : inverse_visibility) {
+ for (set<int>::const_iterator camera1 = inverse_visibility_set.begin();
+ camera1 != inverse_visibility_set.end();
+ ++camera1) {
+ set<int>::const_iterator camera2 = camera1;
+ for (++camera2; camera2 != inverse_visibility_set.end(); ++camera2) {
+ ++(camera_pairs[make_pair(*camera1, *camera2)]);
+ }
+ }
+ }
+
+ WeightedGraph<int>* graph = new WeightedGraph<int>;
+
+ // Add vertices and initialize the pairs for self edges so that self
+ // edges are guaranteed. This is needed for the Canonical views
+ // algorithm to work correctly.
+ static const double kSelfEdgeWeight = 1.0;
+ for (int i = 0; i < visibility.size(); ++i) {
+ graph->AddVertex(i);
+ graph->AddEdge(i, i, kSelfEdgeWeight);
+ }
+
+ // Add an edge for each camera pair.
+ for (const auto& camera_pair_count : camera_pairs) {
+ const int camera1 = camera_pair_count.first.first;
+ const int camera2 = camera_pair_count.first.second;
+ const int count = camera_pair_count.second;
+ DCHECK_NE(camera1, camera2);
+ // Static cast necessary for Windows.
+ const double weight = static_cast<double>(count) /
+ (sqrt(static_cast<double>(
+ visibility[camera1].size() * visibility[camera2].size())));
+ graph->AddEdge(camera1, camera2, weight);
+ }
+
+ VLOG(2) << "Schur complement graph time: " << (time(NULL) - start_time);
+ return graph;
+}
+
+} // namespace internal
+} // namespace ceres