GridDecomposition.cpp
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34 
35 /* Author: Matt Maly */
36 
37 #include "ompl/control/planners/syclop/GridDecomposition.h"
38 
39 namespace
40 {
42  static int calcNumGridCells(int len, int dim);
43 }
44 
46  : Decomposition(dim, b), length_(len), cellVolume_(b.getVolume()), numGridCells_(calcNumGridCells(len, dim))
47 {
48  double lenInv = 1.0 / len;
49  for (int i = 0; i < dim; ++i)
50  cellVolume_ *= lenInv;
51 }
52 
53 void ompl::control::GridDecomposition::getNeighbors(int rid, std::vector<int> &neighbors) const
54 {
55  // We efficiently compute neighbors for dim = 1, 2, or 3; for higher dimensions we use a general approach.
56  if (dimension_ == 1)
57  {
58  if (rid > 0)
59  neighbors.push_back(rid - 1);
60  if (rid < length_ - 1)
61  neighbors.push_back(rid + 1);
62  }
63  else if (dimension_ == 2)
64  {
65  static const int offset[] = {-1, -1, 0, -1, +1, -1, -1, 0, +1, 0, -1, +1, 0, +1, +1, +1};
66  std::vector<int> coord(2);
67  regionToGridCoord(rid, coord);
68  std::vector<int> nc(2);
69  for (std::size_t i = 0; i < 16; i += 2)
70  {
71  nc[0] = coord[0] + offset[i];
72  nc[1] = coord[1] + offset[i + 1];
73  if (nc[0] >= 0 && (int)nc[0] < length_ && nc[1] >= 0 && (int)nc[1] < length_)
74  neighbors.push_back(nc[0] * length_ + nc[1]);
75  }
76  }
77  else if (dimension_ == 3)
78  {
79  static const int offset[] = {-1, 0, 0, +1, 0, 0, 0, -1, 0, 0, +1, 0, -1, -1, 0, -1, +1, 0, +1, -1,
80  0, +1, +1, 0, -1, 0, -1, +1, 0, -1, 0, -1, -1, 0, +1, -1, -1, -1, -1, -1,
81  +1, -1, +1, -1, -1, +1, +1, -1, -1, 0, +1, +1, 0, +1, 0, -1, +1, 0, +1, +1,
82  -1, -1, +1, -1, +1, +1, +1, -1, +1, +1, +1, +1, 0, 0, -1, 0, 0, +1};
83  std::vector<int> coord(3);
84  regionToGridCoord(rid, coord);
85  std::vector<int> nc(3);
86  for (int i = 0; i < 78; i += 3)
87  {
88  nc[0] = coord[0] + offset[i];
89  nc[1] = coord[1] + offset[i + 1];
90  nc[2] = coord[2] + offset[i + 2];
91  if (nc[0] >= 0 && (int)nc[0] < length_ && nc[1] >= 0 && (int)nc[1] < length_ && nc[2] >= 0 &&
92  (int)nc[2] < length_)
93  neighbors.push_back(nc[0] * length_ * length_ + nc[1] * length_ + nc[2]);
94  }
95  }
96  else
97  {
98  computeGridNeighbors(rid, neighbors);
99  }
100 }
101 
103 {
104  std::vector<double> coord(dimension_);
105  project(s, coord);
106  return coordToRegion(coord);
107 }
108 
109 void ompl::control::GridDecomposition::sampleFromRegion(int rid, RNG &rng, std::vector<double> &coord) const
110 {
111  coord.resize(dimension_);
112  const base::RealVectorBounds &regionBounds(getRegionBounds(rid));
113  for (int i = 0; i < dimension_; ++i)
114  coord[i] = rng.uniformReal(regionBounds.low[i], regionBounds.high[i]);
115 }
116 
117 void ompl::control::GridDecomposition::computeGridNeighbors(int rid, std::vector<int> &neighbors) const
118 {
119  std::vector<int> candidate(dimension_, -1);
120  std::vector<int> coord;
121  regionToGridCoord(rid, coord);
122 
123  computeGridNeighborsSub(coord, neighbors, 0, candidate);
124 }
125 
127  std::vector<int> &neighbors, int dim,
128  std::vector<int> &candidate) const
129 {
130  // Stopping condition for recursive method.
131  if (dim == dimension_)
132  {
133  // Make sure we don't push back ourselves as a neighbor
134  bool same = true;
135  for (unsigned int i = 0; i < coord.size() && same; ++i)
136  same = (coord[i] == candidate[i]);
137 
138  if (!same)
139  {
140  neighbors.push_back(gridCoordToRegion(candidate));
141  }
142  }
143  else
144  {
145  // Check neighbor in the cell preceding this one in this dimension
146  if (coord[dim] >= 1)
147  {
148  candidate[dim] = coord[dim] - 1;
149  computeGridNeighborsSub(coord, neighbors, dim + 1, candidate);
150  }
151 
152  // Make sure to include the same coordinate, for neighbors "above", "below", "in front of", "behind", etcetera.
153  candidate[dim] = coord[dim];
154  computeGridNeighborsSub(coord, neighbors, dim + 1, candidate);
155 
156  // Check neighbor in the cell after this one in this dimension
157  if (coord[dim] + 1 < length_)
158  {
159  candidate[dim] = coord[dim] + 1;
160  computeGridNeighborsSub(coord, neighbors, dim + 1, candidate);
161  }
162  }
163 }
164 
165 void ompl::control::GridDecomposition::regionToGridCoord(int rid, std::vector<int> &coord) const
166 {
167  coord.resize(dimension_);
168  for (int i = dimension_ - 1; i >= 0; --i)
169  {
170  int remainder = rid % length_;
171  coord[i] = remainder;
172  rid /= length_;
173  }
174 }
175 
176 int ompl::control::GridDecomposition::gridCoordToRegion(const std::vector<int> &coord) const
177 {
178  int region = 0;
179  for (unsigned int i = 0; i < coord.size(); i++)
180  {
181  // Computing length_^(dimension of coord -1)
182  int multiplicand = 1;
183  for (unsigned int j = 1; j < coord.size() - i; j++)
184  multiplicand *= length_;
185 
186  region += (coord[i] * multiplicand);
187  }
188  return region;
189 }
190 
191 int ompl::control::GridDecomposition::coordToRegion(const std::vector<double> &coord) const
192 {
193  int region = 0;
194  int factor = 1;
195  int index;
196  for (int i = dimension_ - 1; i >= 0; --i)
197  {
198  index = (int)(length_ * (coord[i] - bounds_.low[i]) / (bounds_.high[i] - bounds_.low[i]));
199 
200  // There is an edge case when the coordinate lies exactly on the upper bound where
201  // the region index will be out of bounds. Ensure index lies within [0, length_)
202  if (index >= length_)
203  index = length_ - 1;
204 
205  region += factor * index;
206  factor *= length_;
207  }
208  return region;
209 }
210 
211 void ompl::control::GridDecomposition::coordToGridCoord(const std::vector<double> &coord,
212  std::vector<int> &gridCoord) const
213 {
214  gridCoord.resize(dimension_);
215  for (int i = 0; i < dimension_; ++i)
216  {
217  gridCoord[i] = (int)(length_ * (coord[i] - bounds_.low[i]) / (bounds_.high[i] - bounds_.low[i]));
218 
219  // There is an edge case when the coordinate lies exactly on the upper bound where
220  // the region index will be out of bounds. Ensure index lies within [0, length_)
221  if (gridCoord[i] >= length_)
222  gridCoord[i] = length_ - 1;
223  }
224 }
225 
227 {
228  if (regToBounds_.count(rid) > 0)
229  return *regToBounds_[rid];
230  auto regionBounds(std::make_shared<ompl::base::RealVectorBounds>(dimension_));
231  std::vector<int> rc(dimension_);
232  regionToGridCoord(rid, rc);
233  for (int i = 0; i < dimension_; ++i)
234  {
235  const double length = (bounds_.high[i] - bounds_.low[i]) / length_;
236  regionBounds->low[i] = bounds_.low[i] + length * rc[i];
237  regionBounds->high[i] = regionBounds->low[i] + length;
238  }
239  regToBounds_[rid] = regionBounds;
240  return *regToBounds_[rid];
241 }
242 
243 namespace
244 {
245  int calcNumGridCells(int len, int dim)
246  {
247  int numCells = 1;
248  for (int i = 0; i < dim; ++i)
249  numCells *= len;
250  return numCells;
251  }
252 }
virtual const base::RealVectorBounds & getRegionBounds(int rid) const
Helper method to return the bounds of a given region.
std::vector< double > low
Lower bound.
void coordToGridCoord(const std::vector< double > &coord, std::vector< int > &gridCoord) const
Converts a decomposition space coordinate to a grid coordinate.
int gridCoordToRegion(const std::vector< int > &coord) const
Converts the given grid coordinate to its corresponding region ID.
int coordToRegion(const std::vector< double > &coord) const
Converts a decomposition space coordinate to the ID of the region that contains iit.
void getNeighbors(int rid, std::vector< int > &neighbors) const override
Stores a given region&#39;s neighbors into a given vector.
A Decomposition is a partition of a bounded Euclidean space into a fixed number of regions which are ...
Definition: Decomposition.h:62
Random number generation. An instance of this class cannot be used by multiple threads at once (membe...
Definition: RandomNumbers.h:58
std::vector< double > high
Upper bound.
double uniformReal(double lower_bound, double upper_bound)
Generate a random real within given bounds: [lower_bound, upper_bound)
Definition: RandomNumbers.h:74
Definition of an abstract state.
Definition: State.h:49
virtual void project(const base::State *s, std::vector< double > &coord) const =0
Project a given State to a set of coordinates in R^k, where k is the dimension of this Decomposition...
GridDecomposition(int len, int dim, const base::RealVectorBounds &b)
Constructor. Creates a GridDecomposition as a hypercube with a given dimension, side length...
The lower and upper bounds for an Rn space.
void sampleFromRegion(int rid, RNG &rng, std::vector< double > &coord) const override
Samples a projected coordinate from a given region.
void regionToGridCoord(int rid, std::vector< int > &coord) const
Converts a given region to a coordinate in the grid.
void computeGridNeighbors(int rid, std::vector< int > &neighbors) const
Computes the neighbors of the given region in a n-dimensional grid.
void computeGridNeighborsSub(const std::vector< int > &coord, std::vector< int > &neighbors, int dim, std::vector< int > &candidate) const
int locateRegion(const base::State *s) const override
Returns the index of the region containing a given State. Most often, this is obtained by first calli...