Follow the same path until another is significantly better

This replaces the cost penalty for routing steps.  In the penalty approach
it was possible to get two or more steps with the same penalty, which
would then race with each other.  In the new approach, all other steps are
sorted by their unpenalized cost and only the preferred one gets special
treatment.

diff --git a/source/libr2c2/trainrouteplanner.cpp b/source/libr2c2/trainrouteplanner.cpp
index e42e61838d4fdc0c7dfa74fe2aa7b451211c8421..d9eedd2d4daccd0d33224548325c594859c7777a 100644 (file)
--- a/source/libr2c2/trainrouteplanner.cpp
+++ b/source/libr2c2/trainrouteplanner.cpp
@@ -16,6 +16,7 @@ namespace R2C2 {
 
 TrainRoutePlanner::TrainRoutePlanner(Layout &layout):
        goal(0),
+       path_switch_bias(15*Time::sec),
        timeout(10*Time::sec),
        result(PENDING),
        thread(0)
@@ -147,7 +148,12 @@ void TrainRoutePlanner::add_steps(const RoutingStep &step)
 {
        list<RoutingStep> new_steps;
        step.create_successors(new_steps);
+       if(new_steps.empty())
+               return;
+
        new_steps.sort();
+       if(!queue.empty() && new_steps.front().cost_estimate<queue.front().cost_estimate+path_switch_bias)
+               new_steps.front().preferred = true;
        queue.merge(new_steps);
 }
 
@@ -518,13 +524,14 @@ bool TrainRoutePlanner::TrainRoutingState::is_viable() const
 
 
 TrainRoutePlanner::RoutingStep::RoutingStep():
+       preferred(false),
        prev(0)
 { }
 
 TrainRoutePlanner::RoutingStep::RoutingStep(const RoutingStep *p):
        time(p->time),
-       penalty(p->penalty),
        cost_estimate(p->cost_estimate),
+       preferred(false),
        trains(p->trains),
        prev(p)
 { }
@@ -570,13 +577,6 @@ void TrainRoutePlanner::RoutingStep::create_successors(list<RoutingStep> &new_st
                                create_successor(next, train_index, i, new_steps);
        }
 
-       new_steps.sort();
-       for(list<RoutingStep>::iterator i=new_steps.begin(); ++i!=new_steps.end(); )
-       {
-               i->penalty += 5*Time::sec;
-               i->update_estimate();
-       }
-
        if(entry_ep.paths!=train.track->get_type().get_paths() && !train.critical)
        {
                /* Create a waiting state before the track if there's at least one path
@@ -719,7 +719,7 @@ void TrainRoutePlanner::RoutingStep::advance(const Time::TimeDelta &dt)
 
 void TrainRoutePlanner::RoutingStep::update_estimate()
 {
-       cost_estimate = penalty;
+       cost_estimate = Time::zero;
        for(vector<TrainRoutingState>::const_iterator i=trains.begin(); i!=trains.end(); ++i)
                if(i->remaining_estimate>=0)
                        cost_estimate += i->wait_time+i->estimated_wait+((i->distance_traveled+i->remaining_estimate)/i->info->speed)*Time::sec;
@@ -748,6 +748,8 @@ bool TrainRoutePlanner::RoutingStep::is_goal() const
 
 bool TrainRoutePlanner::RoutingStep::operator<(const RoutingStep &other) const
 {
+       if(preferred!=other.preferred)
+               return preferred>other.preferred;
        return cost_estimate<other.cost_estimate;
 }
 

diff --git a/source/libr2c2/trainrouteplanner.h b/source/libr2c2/trainrouteplanner.h
index 79a6036e6d1fbe5b8c7a6c23a70f616a8d6c6216..32c9dadc3494671dcbe805c6fcf1ff4bee5b5247 100644 (file)
--- a/source/libr2c2/trainrouteplanner.h
+++ b/source/libr2c2/trainrouteplanner.h
@@ -103,8 +103,8 @@ private:
        struct RoutingStep
        {
                Msp::Time::TimeDelta time;
-               Msp::Time::TimeDelta penalty;
                Msp::Time::TimeDelta cost_estimate;
+               bool preferred;
                std::vector<TrainRoutingState> trains;
                const RoutingStep *prev;
 
@@ -141,6 +141,7 @@ private:
        std::list<RoutingStep> steps;
        std::list<RoutingStep> queue;
        const RoutingStep *goal;
+       Msp::Time::TimeDelta path_switch_bias;
        Msp::Time::TimeDelta timeout;
        Result result;
        PlanningThread *thread;