LTLPlanner.cpp

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/* Author: Matt Maly */
 
#include "ompl/control/planners/ltl/LTLPlanner.h"
#include "ompl/control/planners/PlannerIncludes.h"
#include "ompl/control/planners/ltl/ProductGraph.h"
#include "ompl/control/planners/ltl/LTLProblemDefinition.h"
#include "ompl/datastructures/PDF.h"
#include "ompl/util/Console.h"
#include <algorithm>
#include <unordered_map>
#include <limits>
#include <map>
#include <utility>
#include <vector>
 
#include <cstdio>
 
ompl::control::LTLPlanner::LTLPlanner(const LTLSpaceInformationPtr &ltlsi, ProductGraphPtr a, double exploreTime)
  : ompl::base::Planner(ltlsi, "LTLPlanner"), ltlsi_(ltlsi.get()), abstraction_(std::move(a)), exploreTime_(exploreTime)
{
    specs_.approximateSolutions = true;
}
 
ompl::control::LTLPlanner::~LTLPlanner()
{
    clearMotions();
}
 
void ompl::control::LTLPlanner::setup()
{
    base::Planner::setup();
}
 
void ompl::control::LTLPlanner::clear()
{
    base::Planner::clear();
    availDist_.clear();
    abstractInfo_.clear();
    clearMotions();
}
 
ompl::base::PlannerStatus ompl::control::LTLPlanner::solve(const ompl::base::PlannerTerminationCondition &ptc)
{
    // \todo make solve work when called more than once!
    checkValidity();
    const base::State *start = pis_.nextStart();
    prodStart_ = ltlsi_->getProdGraphState(start);
 
    if (pis_.haveMoreStartStates())
        OMPL_WARN("Multiple start states given. Using only the first start state.");
 
    auto *startMotion = new Motion(ltlsi_);
    si_->copyState(startMotion->state, start);
    ltlsi_->nullControl(startMotion->control);
    startMotion->abstractState = prodStart_;
 
    motions_.push_back(startMotion);
    abstractInfo_[prodStart_].addMotion(startMotion);
    updateWeight(prodStart_);
    availDist_.add(prodStart_, abstractInfo_[prodStart_].weight);
 
    abstraction_->buildGraph(prodStart_, [this](ProductGraph::State *as) { initAbstractInfo(as); });
 
    if (!sampler_)
        sampler_ = si_->allocStateSampler();
    if (!controlSampler_)
        controlSampler_ = ltlsi_->allocControlSampler();
 
    bool solved = false;
    Motion *soln;
 
    while (ptc() == false && !solved)
    {
        const std::vector<ProductGraph::State *> lead = abstraction_->computeLead(
            prodStart_, [this](ProductGraph::State *a, ProductGraph::State *b) { return abstractEdgeWeight(a, b); });
        buildAvail(lead);
        solved = explore(lead, soln, exploreTime_);
    }
 
    if (solved)
    {
        // build solution path
        std::vector<Motion *> path;
        while (soln != nullptr)
        {
            path.push_back(soln);
            soln = soln->parent;
        }
        auto pc(std::make_shared<PathControl>(si_));
        for (int i = path.size() - 1; i >= 0; --i)
        {
            if (path[i]->parent != nullptr)
                pc->append(path[i]->state, path[i]->control, path[i]->steps * ltlsi_->getPropagationStepSize());
            else
                pc->append(path[i]->state);
        }
        pdef_->addSolutionPath(pc);
    }
 
    OMPL_INFORM("Created %u states", motions_.size());
    return {solved, false};
}
 
void ompl::control::LTLPlanner::getTree(std::vector<base::State *> &tree) const
{
    tree.resize(motions_.size());
    for (unsigned int i = 0; i < motions_.size(); ++i)
        tree[i] = motions_[i]->state;
}
 
std::vector<ompl::control::ProductGraph::State *>
ompl::control::LTLPlanner::getHighLevelPath(const std::vector<base::State *> &path, ProductGraph::State *start) const
{
    std::vector<ProductGraph::State *> hlPath(path.size());
    hlPath[0] = (start != nullptr ? start : ltlsi_->getProdGraphState(path[0]));
    for (unsigned int i = 1; i < path.size(); ++i)
    {
        hlPath[i] = ltlsi_->getProdGraphState(path[i]);
        if (!hlPath[i]->isValid())
            OMPL_WARN("High-level path fails automata");
    }
    return hlPath;
}
 
ompl::control::LTLPlanner::Motion::Motion(const SpaceInformation *si)
  : state(si->allocState()), control(si->allocControl())
{
}
 
ompl::control::LTLPlanner::Motion::~Motion() = default;
 
void ompl::control::LTLPlanner::ProductGraphStateInfo::addMotion(Motion *m)
{
    motionElems[m] = motions.add(m, 1.);
}
 
double ompl::control::LTLPlanner::updateWeight(ProductGraph::State *as)
{
    ProductGraphStateInfo &info = abstractInfo_[as];
    /* \todo weight should include freeVolume, for cases in which decomposition
       does not respect obstacles. */
    info.weight = ((info.motions.size() + 1) * info.volume) / (info.autWeight * (info.numSel + 1) * (info.numSel + 1));
    return info.weight;
}
 
void ompl::control::LTLPlanner::initAbstractInfo(ProductGraph::State *as)
{
    ProductGraphStateInfo &info = abstractInfo_[as];
    info.numSel = 0;
    info.pdfElem = nullptr;
    info.volume = abstraction_->getRegionVolume(as);
    unsigned int autDist = std::max(abstraction_->getCosafeAutDistance(as), abstraction_->getSafeAutDistance(as));
    //\todo try something larger than epsilon
    if (autDist == 0)
        info.autWeight = std::numeric_limits<double>::epsilon();
    else
        info.autWeight = autDist;
    info.weight = info.volume / info.autWeight;
}
 
void ompl::control::LTLPlanner::buildAvail(const std::vector<ProductGraph::State *> &lead)
{
    for (unsigned int i = 0; i < availDist_.size(); ++i)
        abstractInfo_[availDist_[i]].pdfElem = nullptr;
    availDist_.clear();
    for (int i = lead.size() - 1; i >= 0; --i)
    {
        ProductGraph::State *as = lead[i];
        ProductGraphStateInfo &info = abstractInfo_[as];
        if (!info.motions.empty())
        {
            info.pdfElem = availDist_.add(as, info.weight);
            if (rng_.uniform01() < 0.5)
                break;
        }
    }
}
 
bool ompl::control::LTLPlanner::explore(const std::vector<ProductGraph::State *> &lead, Motion *&soln, double duration)
{
    bool solved = false;
    base::PlannerTerminationCondition ptc = base::timedPlannerTerminationCondition(duration);
    base::GoalPtr goal = pdef_->getGoal();
    while (!ptc() && !solved)
    {
        ProductGraph::State *as = availDist_.sample(rng_.uniform01());
        ++abstractInfo_[as].numSel;
        updateWeight(as);
 
        PDF<Motion *> &motions = abstractInfo_[as].motions;
        Motion *v = motions.sample(rng_.uniform01());
        PDF<Motion *>::Element *velem = abstractInfo_[as].motionElems[v];
        double vweight = motions.getWeight(velem);
        if (vweight > 1e-20)
            motions.update(velem, vweight / (vweight + 1.));
 
        Control *rctrl = ltlsi_->allocControl();
        controlSampler_->sampleNext(rctrl, v->control, v->state);
        unsigned int cd =
            controlSampler_->sampleStepCount(ltlsi_->getMinControlDuration(), ltlsi_->getMaxControlDuration());
 
        base::State *newState = si_->allocState();
        cd = ltlsi_->propagateWhileValid(v->state, rctrl, cd, newState);
        if (cd < ltlsi_->getMinControlDuration())
        {
            si_->freeState(newState);
            ltlsi_->freeControl(rctrl);
            continue;
        }
        auto *m = new Motion();
        m->state = newState;
        m->control = rctrl;
        m->steps = cd;
        m->parent = v;
        // Since the state was determined to be valid by SpaceInformation, we don't need to check automaton states
        m->abstractState = ltlsi_->getProdGraphState(m->state);
        motions_.push_back(m);
 
        abstractInfo_[m->abstractState].addMotion(m);
        updateWeight(m->abstractState);
        // update weight if hl state already exists in avail
        if (abstractInfo_[m->abstractState].pdfElem != nullptr)
            availDist_.update(abstractInfo_[m->abstractState].pdfElem, abstractInfo_[m->abstractState].weight);
        else
        {
            // otherwise, only add hl state to avail if it already exists in lead
            if (std::find(lead.begin(), lead.end(), m->abstractState) != lead.end())
            {
                PDF<ProductGraph::State *>::Element *elem =
                    availDist_.add(m->abstractState, abstractInfo_[m->abstractState].weight);
                abstractInfo_[m->abstractState].pdfElem = elem;
            }
        }
 
        solved = goal->isSatisfied(m->state);
        if (solved)
        {
            soln = m;
            break;
        }
    }
    return solved;
}
 
double ompl::control::LTLPlanner::abstractEdgeWeight(ProductGraph::State *a, ProductGraph::State *b) const
{
    const ProductGraphStateInfo &infoA = abstractInfo_.find(a)->second;
    const ProductGraphStateInfo &infoB = abstractInfo_.find(b)->second;
    return 1. / (infoA.weight * infoB.weight);
}
 
void ompl::control::LTLPlanner::clearMotions()
{
    availDist_.clear();
    for (auto m : motions_)
    {
        if (m->state != nullptr)
            si_->freeState(m->state);
        if (m->control != nullptr)
            ltlsi_->freeControl(m->control);
        delete m;
    }
    motions_.clear();
    pis_.clear();
    pis_.update();
}