SST.cpp

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/* Authors: Zakary Littlefield */
 
#include "ompl/control/planners/sst/SST.h"
#include "ompl/base/goals/GoalSampleableRegion.h"
#include "ompl/base/objectives/MinimaxObjective.h"
#include "ompl/base/objectives/MaximizeMinClearanceObjective.h"
#include "ompl/base/objectives/PathLengthOptimizationObjective.h"
#include "ompl/base/objectives/MechanicalWorkOptimizationObjective.h"
#include "ompl/tools/config/SelfConfig.h"
#include <limits>
 
ompl::control::SST::SST(const SpaceInformationPtr &si) : base::Planner(si, "SST")
{
    specs_.approximateSolutions = true;
    siC_ = si.get();
    prevSolution_.clear();
    prevSolutionControls_.clear();
    prevSolutionSteps_.clear();
 
    Planner::declareParam<double>("goal_bias", this, &SST::setGoalBias, &SST::getGoalBias, "0.:.05:1.");
    Planner::declareParam<double>("selection_radius", this, &SST::setSelectionRadius, &SST::getSelectionRadius, "0.:.1:"
                                                                                                                "100");
    Planner::declareParam<double>("pruning_radius", this, &SST::setPruningRadius, &SST::getPruningRadius, "0.:.1:100");
}
 
ompl::control::SST::~SST()
{
    freeMemory();
}
 
void ompl::control::SST::setup()
{
    base::Planner::setup();
    if (!nn_)
        nn_.reset(tools::SelfConfig::getDefaultNearestNeighbors<Motion *>(this));
    nn_->setDistanceFunction([this](const Motion *a, const Motion *b)
                             {
                                 return distanceFunction(a, b);
                             });
    if (!witnesses_)
        witnesses_.reset(tools::SelfConfig::getDefaultNearestNeighbors<Motion *>(this));
    witnesses_->setDistanceFunction([this](const Motion *a, const Motion *b)
                                    {
                                        return distanceFunction(a, b);
                                    });
 
    if (pdef_)
    {
        if (pdef_->hasOptimizationObjective())
        {
            opt_ = pdef_->getOptimizationObjective();
            if (dynamic_cast<base::MaximizeMinClearanceObjective *>(opt_.get()) ||
                dynamic_cast<base::MinimaxObjective *>(opt_.get()))
                OMPL_WARN("%s: Asymptotic near-optimality has only been proven with Lipschitz continuous cost "
                          "functions w.r.t. state and control. This optimization objective will result in undefined "
                          "behavior",
                          getName().c_str());
        }
        else
        {
            OMPL_WARN("%s: No optimization object set. Using path length", getName().c_str());
            opt_ = std::make_shared<base::PathLengthOptimizationObjective>(si_);
            pdef_->setOptimizationObjective(opt_);
        }
    }
 
    prevSolutionCost_ = opt_->infiniteCost();
}
 
void ompl::control::SST::clear()
{
    Planner::clear();
    sampler_.reset();
    controlSampler_.reset();
    freeMemory();
    if (nn_)
        nn_->clear();
    if (witnesses_)
        witnesses_->clear();
    if (opt_)
        prevSolutionCost_ = opt_->infiniteCost();
}
 
void ompl::control::SST::freeMemory()
{
    if (nn_)
    {
        std::vector<Motion *> motions;
        nn_->list(motions);
        for (auto &motion : motions)
        {
            if (motion->state_)
                si_->freeState(motion->state_);
            if (motion->control_)
                siC_->freeControl(motion->control_);
            delete motion;
        }
    }
    if (witnesses_)
    {
        std::vector<Motion *> witnesses;
        witnesses_->list(witnesses);
        for (auto &witness : witnesses)
        {
            delete witness;
        }
    }
    for (auto &i : prevSolution_)
    {
        if (i)
            si_->freeState(i);
    }
    prevSolution_.clear();
    for (auto &prevSolutionControl : prevSolutionControls_)
    {
        if (prevSolutionControl)
            siC_->freeControl(prevSolutionControl);
    }
    prevSolutionControls_.clear();
    prevSolutionSteps_.clear();
}
 
ompl::control::SST::Motion *ompl::control::SST::selectNode(ompl::control::SST::Motion *sample)
{
    std::vector<Motion *> ret;
    Motion *selected = nullptr;
    base::Cost bestCost = opt_->infiniteCost();
    nn_->nearestR(sample, selectionRadius_, ret);
    for (auto &i : ret)
    {
        if (!i->inactive_ && opt_->isCostBetterThan(i->accCost_, bestCost))
        {
            bestCost = i->accCost_;
            selected = i;
        }
    }
    if (selected == nullptr)
    {
        int k = 1;
        while (selected == nullptr)
        {
            nn_->nearestK(sample, k, ret);
            for (unsigned int i = 0; i < ret.size() && selected == nullptr; i++)
                if (!ret[i]->inactive_)
                    selected = ret[i];
            k += 5;
        }
    }
    return selected;
}
 
ompl::control::SST::Witness *ompl::control::SST::findClosestWitness(ompl::control::SST::Motion *node)
{
    if (witnesses_->size() > 0)
    {
        auto *closest = static_cast<Witness *>(witnesses_->nearest(node));
        if (distanceFunction(closest, node) > pruningRadius_)
        {
            closest = new Witness(siC_);
            closest->linkRep(node);
            si_->copyState(closest->state_, node->state_);
            witnesses_->add(closest);
        }
        return closest;
    }
    else
    {
        auto *closest = new Witness(siC_);
        closest->linkRep(node);
        si_->copyState(closest->state_, node->state_);
        witnesses_->add(closest);
        return closest;
    }
}
 
ompl::base::PlannerStatus ompl::control::SST::solve(const base::PlannerTerminationCondition &ptc)
{
    checkValidity();
    base::Goal *goal = pdef_->getGoal().get();
    auto *goal_s = dynamic_cast<base::GoalSampleableRegion *>(goal);
 
    while (const base::State *st = pis_.nextStart())
    {
        auto *motion = new Motion(siC_);
        si_->copyState(motion->state_, st);
        siC_->nullControl(motion->control_);
        nn_->add(motion);
        motion->accCost_ = opt_->identityCost();
        findClosestWitness(motion);
    }
 
    if (nn_->size() == 0)
    {
        OMPL_ERROR("%s: There are no valid initial states!", getName().c_str());
        return base::PlannerStatus::INVALID_START;
    }
 
    if (!sampler_)
        sampler_ = si_->allocStateSampler();
    if (!controlSampler_)
        controlSampler_ = siC_->allocControlSampler();
 
    const base::ReportIntermediateSolutionFn intermediateSolutionCallback = pdef_->getIntermediateSolutionCallback();
 
    OMPL_INFORM("%s: Starting planning with %u states already in datastructure\n", getName().c_str(), nn_->size());
 
    Motion *solution = nullptr;
    Motion *approxsol = nullptr;
    double approxdif = std::numeric_limits<double>::infinity();
    bool sufficientlyShort = false;
 
    auto *rmotion = new Motion(siC_);
    base::State *rstate = rmotion->state_;
    Control *rctrl = rmotion->control_;
    base::State *xstate = si_->allocState();
 
    unsigned iterations = 0;
 
    while (ptc == false)
    {
        /* sample random state (with goal biasing) */
        if (goal_s && rng_.uniform01() < goalBias_ && goal_s->canSample())
            goal_s->sampleGoal(rstate);
        else
            sampler_->sampleUniform(rstate);
 
        /* find closest state in the tree */
        Motion *nmotion = selectNode(rmotion);
 
        /* sample a random control that attempts to go towards the random state, and also sample a control duration */
        controlSampler_->sample(rctrl);
        unsigned int cd = rng_.uniformInt(siC_->getMinControlDuration(), siC_->getMaxControlDuration());
        unsigned int propCd = siC_->propagateWhileValid(nmotion->state_, rctrl, cd, rstate);
 
        if (propCd == cd)
        {
            base::Cost incCostMotion = opt_->motionCost(nmotion->state_, rstate);
            base::Cost incCostControl = opt_->controlCost(rctrl, cd);
            base::Cost incCost = opt_->combineCosts(incCostMotion, incCostControl);
            base::Cost cost = opt_->combineCosts(nmotion->accCost_, incCost);
            Witness *closestWitness = findClosestWitness(rmotion);
 
            if (closestWitness->rep_ == rmotion || opt_->isCostBetterThan(cost, closestWitness->rep_->accCost_))
            {
                Motion *oldRep = closestWitness->rep_;
                /* create a motion */
                auto *motion = new Motion(siC_);
                motion->accCost_ = cost;
                si_->copyState(motion->state_, rmotion->state_);
                siC_->copyControl(motion->control_, rctrl);
                motion->steps_ = cd;
                motion->parent_ = nmotion;
                nmotion->numChildren_++;
                closestWitness->linkRep(motion);
 
                nn_->add(motion);
                double dist = 0.0;
                bool solv = goal->isSatisfied(motion->state_, &dist);
                if (solv && opt_->isCostBetterThan(motion->accCost_, prevSolutionCost_))
                {
                    approxdif = dist;
                    solution = motion;
 
                    for (auto &i : prevSolution_)
                        if (i)
                            si_->freeState(i);
                    prevSolution_.clear();
                    for (auto &prevSolutionControl : prevSolutionControls_)
                        if (prevSolutionControl)
                            siC_->freeControl(prevSolutionControl);
                    prevSolutionControls_.clear();
                    prevSolutionSteps_.clear();
 
                    Motion *solTrav = solution;
                    while (solTrav->parent_ != nullptr)
                    {
                        prevSolution_.push_back(si_->cloneState(solTrav->state_));
                        prevSolutionControls_.push_back(siC_->cloneControl(solTrav->control_));
                        prevSolutionSteps_.push_back(solTrav->steps_);
                        solTrav = solTrav->parent_;
                    }
                    prevSolution_.push_back(si_->cloneState(solTrav->state_));
                    prevSolutionCost_ = solution->accCost_;
 
                    OMPL_INFORM("Found solution with cost %.2f", solution->accCost_.value());
                    if (intermediateSolutionCallback)
                    {
                        // the callback requires a vector with const elements -> create a copy
                        std::vector<const base::State *> prevSolutionConst(prevSolution_.begin(), prevSolution_.end());
                        intermediateSolutionCallback(this, prevSolutionConst, prevSolutionCost_);
                    }
                    sufficientlyShort = opt_->isSatisfied(solution->accCost_);
                    if (sufficientlyShort)
                        break;
                }
                if (solution == nullptr && dist < approxdif)
                {
                    approxdif = dist;
                    approxsol = motion;
 
                    for (auto &i : prevSolution_)
                        if (i)
                            si_->freeState(i);
                    prevSolution_.clear();
                    for (auto &prevSolutionControl : prevSolutionControls_)
                        if (prevSolutionControl)
                            siC_->freeControl(prevSolutionControl);
                    prevSolutionControls_.clear();
                    prevSolutionSteps_.clear();
 
                    Motion *solTrav = approxsol;
                    while (solTrav->parent_ != nullptr)
                    {
                        prevSolution_.push_back(si_->cloneState(solTrav->state_));
                        prevSolutionControls_.push_back(siC_->cloneControl(solTrav->control_));
                        prevSolutionSteps_.push_back(solTrav->steps_);
                        solTrav = solTrav->parent_;
                    }
                    prevSolution_.push_back(si_->cloneState(solTrav->state_));
                }
 
                if (oldRep != rmotion)
                {
                    while (oldRep->inactive_ && oldRep->numChildren_ == 0)
                    {
                        oldRep->inactive_ = true;
                        nn_->remove(oldRep);
 
                        if (oldRep->state_)
                            si_->freeState(oldRep->state_);
                        if (oldRep->control_)
                            siC_->freeControl(oldRep->control_);
 
                        oldRep->state_ = nullptr;
                        oldRep->control_ = nullptr;
                        oldRep->parent_->numChildren_--;
                        Motion *oldRepParent = oldRep->parent_;
                        delete oldRep;
                        oldRep = oldRepParent;
                    }
                }
            }
        }
        iterations++;
    }
 
    bool solved = false;
    bool approximate = false;
    if (solution == nullptr)
    {
        solution = approxsol;
        approximate = true;
    }
 
    if (solution != nullptr)
    {
        /* set the solution path */
        auto path(std::make_shared<PathControl>(si_));
        for (int i = prevSolution_.size() - 1; i >= 1; --i)
            path->append(prevSolution_[i], prevSolutionControls_[i - 1],
                         prevSolutionSteps_[i - 1] * siC_->getPropagationStepSize());
        path->append(prevSolution_[0]);
        solved = true;
        pdef_->addSolutionPath(path, approximate, approxdif, getName());
    }
 
    si_->freeState(xstate);
    if (rmotion->state_)
        si_->freeState(rmotion->state_);
    if (rmotion->control_)
        siC_->freeControl(rmotion->control_);
    delete rmotion;
 
    OMPL_INFORM("%s: Created %u states in %u iterations", getName().c_str(), nn_->size(), iterations);
 
    return {solved, approximate};
}
 
void ompl::control::SST::getPlannerData(base::PlannerData &data) const
{
    Planner::getPlannerData(data);
 
    std::vector<Motion *> motions;
    std::vector<Motion *> allMotions;
    if (nn_)
        nn_->list(motions);
 
    for (auto &motion : motions)
    {
        if (motion->numChildren_ == 0)
        {
            allMotions.push_back(motion);
        }
    }
    for (unsigned i = 0; i < allMotions.size(); i++)
    {
        if (allMotions[i]->parent_ != nullptr)
        {
            allMotions.push_back(allMotions[i]->parent_);
        }
    }
 
    double delta = siC_->getPropagationStepSize();
 
    if (prevSolution_.size() != 0)
        data.addGoalVertex(base::PlannerDataVertex(prevSolution_[0]));
 
    for (auto m : allMotions)
    {
        if (m->parent_)
        {
            if (data.hasControls())
                data.addEdge(base::PlannerDataVertex(m->parent_->state_), base::PlannerDataVertex(m->state_),
                             control::PlannerDataEdgeControl(m->control_, m->steps_ * delta));
            else
                data.addEdge(base::PlannerDataVertex(m->parent_->state_), base::PlannerDataVertex(m->state_));
        }
        else
            data.addStartVertex(base::PlannerDataVertex(m->state_));
    }
}