ompl::geometric::PRM Class Reference

#include <ompl/geometric/planners/prm/PRM.h>

Inheritance diagram for ompl::geometric::PRM:

## Classes

struct  vertex_state_t

struct  vertex_successful_connection_attempts_t

struct  vertex_total_connection_attempts_t

## Public Types

using Graph = boost::adjacency_list< boost::vecS, boost::vecS, boost::undirectedS, boost::property< vertex_state_t, base::State *, boost::property< vertex_total_connection_attempts_t, unsigned long int, boost::property< vertex_successful_connection_attempts_t, unsigned long int, boost::property< boost::vertex_predecessor_t, unsigned long int, boost::property< boost::vertex_rank_t, unsigned long int > >> >>, boost::property< boost::edge_weight_t, base::Cost > >

using Vertex = boost::graph_traits< Graph >::vertex_descriptor
The type for a vertex in the roadmap.

using Edge = boost::graph_traits< Graph >::edge_descriptor
The type for an edge in the roadmap.

using RoadmapNeighbors = std::shared_ptr< NearestNeighbors< Vertex > >
A nearest neighbors data structure for roadmap vertices.

using ConnectionStrategy = std::function< const std::vector< Vertex > &(const Vertex)>
A function returning the milestones that should be attempted to connect to.

using ConnectionFilter = std::function< bool(const Vertex &, const Vertex &)>
A function that can reject connections. More...

Public Types inherited from ompl::base::Planner
using PlannerProgressProperty = std::function< std::string()>
Definition of a function which returns a property about the planner's progress that can be queried by a benchmarking routine.

using PlannerProgressProperties = std::map< std::string, PlannerProgressProperty >
A dictionary which maps the name of a progress property to the function to be used for querying that property.

## Public Member Functions

PRM (const base::SpaceInformationPtr &si, bool starStrategy=false)
Constructor.

PRM (const base::PlannerData &data, bool starStrategy=false)
Constructor.

void setProblemDefinition (const base::ProblemDefinitionPtr &pdef) override

void setConnectionStrategy (const ConnectionStrategy &connectionStrategy)
Set the connection strategy function that specifies the milestones that connection attempts will be make to for a given milestone. More...

void setDefaultConnectionStrategy ()

void setMaxNearestNeighbors (unsigned int k)
Convenience function that sets the connection strategy to the default one with k nearest neighbors.

unsigned int getMaxNearestNeighbors () const
return the maximum number of nearest neighbors to connect a sample to More...

void setConnectionFilter (const ConnectionFilter &connectionFilter)
Set the function that can reject a milestone connection. More...

void getPlannerData (base::PlannerData &data) const override
Get information about the current run of the motion planner. Repeated calls to this function will update data (only additions are made). This is useful to see what changed in the exploration datastructure, between calls to solve(), for example (without calling clear() in between).

While the termination condition allows, this function will construct the roadmap (using growRoadmap() and expandRoadmap(), maintaining a 2:1 ratio for growing/expansion of roadmap)

If the user desires, the roadmap can be improved for the given time (seconds). The solve() method will also improve the roadmap, as needed.

If the user desires, the roadmap can be improved until a given condition is true. The solve() method will also improve the roadmap, as needed.

Attempt to connect disjoint components in the roadmap using random bouncing motions (the PRM expansion step) for the given time (seconds).

Attempt to connect disjoint components in the roadmap using random bouncing motions (the PRM expansion step) until the given condition evaluates true.

base::PlannerStatus solve (const base::PlannerTerminationCondition &ptc) override
Function that can solve the motion planning problem. Grows a roadmap using constructRoadmap(). This function can be called multiple times on the same problem, without calling clear() in between. This allows the planner to continue work for more time on an unsolved problem, for example. Start and goal states from the currently specified ProblemDefinition are cached. This means that between calls to solve(), input states are only added, not removed. When using PRM as a multi-query planner, the input states should be however cleared, without clearing the roadmap itself. This can be done using the clearQuery() function.

void clearQuery () override
Clear the query previously loaded from the ProblemDefinition. Subsequent calls to solve() will reuse the previously computed roadmap, but will clear the set of input states constructed by the previous call to solve(). This enables multi-query functionality for PRM.

void clear () override
Clear all internal datastructures. Planner settings are not affected. Subsequent calls to solve() will ignore all previous work.

template<template< typename T > class NN>
void setNearestNeighbors ()
Set a different nearest neighbors datastructure.

void setup () override
Perform extra configuration steps, if needed. This call will also issue a call to ompl::base::SpaceInformation::setup() if needed. This must be called before solving.

unsigned long int milestoneCount () const
Return the number of milestones currently in the graph.

unsigned long int edgeCount () const
Return the number of edges currently in the graph.

Public Member Functions inherited from ompl::base::Planner
Planner (const Planner &)=delete

Planneroperator= (const Planner &)=delete

Planner (SpaceInformationPtr si, std::string name)
Constructor.

virtual ~Planner ()=default
Destructor.

template<class T >
T * as ()
Cast this instance to a desired type. More...

template<class T >
const T * as () const
Cast this instance to a desired type. More...

const SpaceInformationPtrgetSpaceInformation () const
Get the space information this planner is using.

const ProblemDefinitionPtrgetProblemDefinition () const
Get the problem definition the planner is trying to solve.

ProblemDefinitionPtrgetProblemDefinition ()
Get the problem definition the planner is trying to solve.

const PlannerInputStatesgetPlannerInputStates () const
Get the planner input states.

virtual void setProblemDefinition (const ProblemDefinitionPtr &pdef)
Set the problem definition for the planner. The problem needs to be set before calling solve(). Note: If this problem definition replaces a previous one, it may also be necessary to call clear() or clearQuery().

PlannerStatus solve (const PlannerTerminationConditionFn &ptc, double checkInterval)
Same as above except the termination condition is only evaluated at a specified interval.

PlannerStatus solve (double solveTime)
Same as above except the termination condition is solely a time limit: the number of seconds the algorithm is allowed to spend planning.

const std::string & getName () const
Get the name of the planner.

void setName (const std::string &name)
Set the name of the planner.

const PlannerSpecsgetSpecs () const
Return the specifications (capabilities of this planner)

virtual void checkValidity ()
Check to see if the planner is in a working state (setup has been called, a goal was set, the input states seem to be in order). In case of error, this function throws an exception.

bool isSetup () const
Check if setup() was called for this planner.

ParamSetparams ()
Get the parameters for this planner.

const ParamSetparams () const
Get the parameters for this planner.

const PlannerProgressPropertiesgetPlannerProgressProperties () const
Retrieve a planner's planner progress property map.

virtual void printProperties (std::ostream &out) const
Print properties of the motion planner.

virtual void printSettings (std::ostream &out) const
Print information about the motion planner's settings.

## Protected Member Functions

void freeMemory ()
Free all the memory allocated by the planner.

Construct a milestone for a given state (state), store it in the nearest neighbors data structure and then connect it to the roadmap in accordance to the connection strategy.

void uniteComponents (Vertex m1, Vertex m2)
Make two milestones (m1 and m2) be part of the same connected component. The component with fewer elements will get the id of the component with more elements.

bool sameComponent (Vertex m1, Vertex m2)
Check if two milestones (m1 and m2) are part of the same connected component. This is not a const function since we use incremental connected components from boost.

void growRoadmap (const base::PlannerTerminationCondition &ptc, base::State *workState)
Randomly sample the state space, add and connect milestones in the roadmap. Stop this process when the termination condition ptc returns true. Use workState as temporary memory.

void expandRoadmap (const base::PlannerTerminationCondition &ptc, std::vector< base::State * > &workStates)
Attempt to connect disjoint components in the roadmap using random bounding motions (the PRM expansion step)

void checkForSolution (const base::PlannerTerminationCondition &ptc, base::PathPtr &solution)

bool maybeConstructSolution (const std::vector< Vertex > &starts, const std::vector< Vertex > &goals, base::PathPtr &solution)
Check if there exists a solution, i.e., there exists a pair of milestones such that the first is in start and the second is in goal, and the two milestones are in the same connected component. If a solution is found, it is constructed in the solution argument.

ompl::base::Cost constructApproximateSolution (const std::vector< Vertex > &starts, const std::vector< Vertex > &goals, base::PathPtr &solution)
(Assuming that there is always an approximate solution), finds an approximate solution.

Returns the value of the addedNewSolution_ member.

base::PathPtr constructSolution (const Vertex &start, const Vertex &goal)
Given two milestones from the same connected component, construct a path connecting them and set it as the solution.

base::Cost costHeuristic (Vertex u, Vertex v) const
Given two vertices, returns a heuristic on the cost of the path connecting them. This method wraps OptimizationObjective::motionCostHeuristic.

double distanceFunction (const Vertex a, const Vertex b) const
Compute distance between two milestones (this is simply distance between the states of the milestones)

std::string getIterationCount () const

std::string getBestCost () const

std::string getMilestoneCountString () const

std::string getEdgeCountString () const

Protected Member Functions inherited from ompl::base::Planner
template<typename T , typename PlannerType , typename SetterType , typename GetterType >
void declareParam (const std::string &name, const PlannerType &planner, const SetterType &setter, const GetterType &getter, const std::string &rangeSuggestion="")
This function declares a parameter for this planner instance, and specifies the setter and getter functions.

template<typename T , typename PlannerType , typename SetterType >
void declareParam (const std::string &name, const PlannerType &planner, const SetterType &setter, const std::string &rangeSuggestion="")
This function declares a parameter for this planner instance, and specifies the setter function.

void addPlannerProgressProperty (const std::string &progressPropertyName, const PlannerProgressProperty &prop)
Add a planner progress property called progressPropertyName with a property querying function prop to this planner's progress property map.

## Protected Attributes

bool starStrategy_
Flag indicating whether the default connection strategy is the Star strategy.

base::ValidStateSamplerPtr sampler_
Sampler user for generating valid samples in the state space.

base::StateSamplerPtr simpleSampler_
Sampler user for generating random in the state space.

Nearest neighbors data structure.

Graph g_
Connectivity graph.

std::vector< VertexstartM_
Array of start milestones.

std::vector< VertexgoalM_
Array of goal milestones.

boost::property_map< Graph, vertex_state_t >::type stateProperty_

boost::property_map< Graph, vertex_total_connection_attempts_t >::type totalConnectionAttemptsProperty_

boost::property_map< Graph, vertex_successful_connection_attempts_t >::type successfulConnectionAttemptsProperty_

boost::property_map< Graph, boost::edge_weight_t >::type weightProperty_

boost::disjoint_sets< boost::property_map< Graph, boost::vertex_rank_t >::type, boost::property_map< Graph, boost::vertex_predecessor_t >::type > disjointSets_
Data structure that maintains the connected components.

ConnectionStrategy connectionStrategy_
Function that returns the milestones to attempt connections with.

ConnectionFilter connectionFilter_
Function that can reject a milestone connection.

bool userSetConnectionStrategy_ {false}
Flag indicating whether the employed connection strategy was set by the user (or defaults are assumed)

RNG rng_
Random number generator.

A flag indicating that a solution has been added during solve()

std::mutex graphMutex_

base::OptimizationObjectivePtr opt_
Objective cost function for PRM graph edges.

unsigned long int iterations_ {0}
Number of iterations the algorithm performed.

base::Cost bestCost_ {std::numeric_limits<double>::quiet_NaN()}
Best cost found so far by algorithm.

Protected Attributes inherited from ompl::base::Planner
SpaceInformationPtr si_
The space information for which planning is done.

ProblemDefinitionPtr pdef_
The user set problem definition.

PlannerInputStates pis_
Utility class to extract valid input states

std::string name_
The name of this planner.

PlannerSpecs specs_
The specifications of the planner (its capabilities)

ParamSet params_
A map from parameter names to parameter instances for this planner. This field is populated by the declareParam() function.

PlannerProgressProperties plannerProgressProperties_
A mapping between this planner's progress property names and the functions used for querying those progress properties.

bool setup_
Flag indicating whether setup() has been called.

## Detailed Description

Short description
PRM is a planner that constructs a roadmap of milestones that approximate the connectivity of the state space. The milestones are valid states in the state space. Near-by milestones are connected by valid motions. Finding a motion plan that connects two given states is reduced to a discrete search (this implementation uses A*) in the roadmap.
External documentation
L.E. Kavraki, P.Švestka, J.-C. Latombe, and M.H. Overmars, Probabilistic roadmaps for path planning in high-dimensional configuration spaces, IEEE Trans. on Robotics and Automation, vol. 12, pp. 566–580, Aug. 1996. DOI: 10.1109/70.508439
[PDF] [more]

Definition at line 80 of file PRM.h.

## ◆ ConnectionFilter

 using ompl::geometric::PRM::ConnectionFilter = std::function

A function that can reject connections.

This is called after previous connections from the neighbor list have been added to the roadmap.

Definition at line 141 of file PRM.h.

## ◆ Graph

 using ompl::geometric::PRM::Graph = boost::adjacency_list< boost::vecS, boost::vecS, boost::undirectedS, boost::property< vertex_state_t, base::State *, boost::property< vertex_total_connection_attempts_t, unsigned long int, boost::property >> >>, boost::property >

Any BGL graph representation could be used here. Because we
Obviously, a ompl::base::State* vertex property is required.
The incremental connected components algorithm requires vertex_predecessor_t and vertex_rank_t properties. If boost::vecS is not used for vertex storage, then there must also be a boost:vertex_index_t property manually added.
Edges should be undirected and have a weight property.

Definition at line 113 of file PRM.h.

## ◆ checkForSolution()

 void ompl::geometric::PRM::checkForSolution ( const base::PlannerTerminationCondition & ptc, base::PathPtr & solution )
protected

Definition at line 379 of file PRM.cpp.

## ◆ getMaxNearestNeighbors()

 unsigned int ompl::geometric::PRM::getMaxNearestNeighbors ( ) const

return the maximum number of nearest neighbors to connect a sample to

This only returns a meaningful answer if the connection strategy is of type KStrategy.

Definition at line 210 of file PRM.cpp.

## ◆ setConnectionFilter()

 void ompl::geometric::PRM::setConnectionFilter ( const ConnectionFilter & connectionFilter )
inline

Set the function that can reject a milestone connection.

The given function is called immediately before a connection
is checked for collision and added to the roadmap. Other neighbors may have already been connected before this function is called. This allows certain heuristics that use the structure of the roadmap (like connected components or useful cycles) to be implemented by changing this function.
Parameters
 connectionFilter A function that takes the new milestone, a neighboring milestone and returns whether a connection should be attempted.

Definition at line 199 of file PRM.h.

## ◆ setConnectionStrategy()

 void ompl::geometric::PRM::setConnectionStrategy ( const ConnectionStrategy & connectionStrategy )
inline

Set the connection strategy function that specifies the milestones that connection attempts will be make to for a given milestone.

The behavior and performance of PRM can be changed drastically
by varying the number and properties if the milestones that are connected to each other.
Parameters
 pdef A function that takes a milestone as an argument and returns a collection of other milestones to which a connection attempt must be made. The default connection strategy is to connect a milestone's 10 closest neighbors.

Definition at line 166 of file PRM.h.

## ◆ setDefaultConnectionStrategy()

 void ompl::geometric::PRM::setDefaultConnectionStrategy ( )

Set default strategy for connecting to nearest neighbors

Definition at line 216 of file PRM.cpp.

The documentation for this class was generated from the following files:
• ompl/geometric/planners/prm/PRM.h
• ompl/geometric/planners/prm/src/PRM.cpp