From 3685f7b18ab52698a8805c86eb192a6e65f9280f Mon Sep 17 00:00:00 2001
From: Dustin Carlino <dabreegster@gmail.com>
Date: Fri, 12 Feb 2021 22:12:46 -0800
Subject: [PATCH] Cache the list of nearby intersections to wake up for
 uber-turns. #497 (#513)

This shouldn't have any behavioral change.
---
 README.md                           |  1 +
 importer/src/bin/generate_houses.rs |  8 +++++--
 sim/src/mechanics/intersection.rs   | 35 +++++++++++++++++++++--------
 3 files changed, 33 insertions(+), 11 deletions(-)

diff --git a/README.md b/README.md
index 1e17ac0c4a..3aa07a03bb 100644
--- a/README.md
+++ b/README.md
@@ -121,6 +121,7 @@ Others:
 - Lots of help with rendering SVG and fonts from
   [RazrFalcon](https://github.com/RazrFalcon) and
   [nical](https://github.com/nical)
+- Lots of traffic signal and uber-turn work from [Bruce](https://github.com/BruceBrown)
 
 Data:
 
diff --git a/importer/src/bin/generate_houses.rs b/importer/src/bin/generate_houses.rs
index d3ed45a6ce..32b064367d 100644
--- a/importer/src/bin/generate_houses.rs
+++ b/importer/src/bin/generate_houses.rs
@@ -6,7 +6,7 @@ use std::collections::HashSet;
 
 use aabb_quadtree::QuadTree;
 use geojson::{Feature, FeatureCollection, GeoJson};
-use rand::{SeedableRng, Rng};
+use rand::{Rng, SeedableRng};
 use rand_xorshift::XorShiftRng;
 
 use abstutil::{CmdArgs, Timer};
@@ -24,7 +24,11 @@ fn main() {
 
     let houses = generate_buildings_on_empty_residential_roads(&map, &mut rng, &mut timer);
     if houses.len() <= num_required {
-        panic!("Only generated {} houses, but wanted at least {}", houses.len(), num_required);
+        panic!(
+            "Only generated {} houses, but wanted at least {}",
+            houses.len(),
+            num_required
+        );
     }
 
     let mut features = Vec::new();
diff --git a/sim/src/mechanics/intersection.rs b/sim/src/mechanics/intersection.rs
index 7cbace547d..cdcba26c2f 100644
--- a/sim/src/mechanics/intersection.rs
+++ b/sim/src/mechanics/intersection.rs
@@ -64,6 +64,9 @@ struct State {
     // complete the entire sequence. This is especially necessary since groups of traffic signals
     // are not yet configured as one.
     reserved: BTreeSet<Request>,
+    // In some cases, a turn completing at one intersection may affect agents waiting to start an
+    // uber-turn at nearby intersections.
+    uber_turn_neighbors: Vec<IntersectionID>,
 
     signal: Option<SignalState>,
 }
@@ -111,11 +114,16 @@ impl IntersectionSimState {
                 accepted: BTreeSet::new(),
                 waiting: BTreeMap::new(),
                 reserved: BTreeSet::new(),
+                uber_turn_neighbors: Vec::new(),
                 signal: None,
             };
             if i.is_traffic_signal() {
                 state.signal = Some(SignalState::new(i.id, Time::START_OF_DAY, map, scheduler));
             }
+            if let Some(mut set) = map_model::IntersectionCluster::autodetect(i.id, map) {
+                set.remove(&i.id);
+                state.uber_turn_neighbors.extend(set);
+            }
             sim.state.insert(i.id, state);
         }
         sim
@@ -130,13 +138,6 @@ impl IntersectionSimState {
         map: &Map,
         handling_live_edits: bool,
     ) {
-        // wake up intersections in the cluster in order to start uber-turns.
-        if let Some(set) = map_model::IntersectionCluster::autodetect(turn.parent, map) {
-            for id in &set {
-                self.wakeup_waiting(now, *id, scheduler, map);
-            }
-        }
-
         let state = self.state.get_mut(&turn.parent).unwrap();
         assert!(state.accepted.remove(&Request { agent, turn }));
         state.reserved.remove(&Request { agent, turn });
@@ -145,11 +146,19 @@ impl IntersectionSimState {
         }
         if self.break_turn_conflict_cycles {
             if let AgentID::Car(car) = agent {
-                // todo: when drain_filter() is no longer experimental, use it instead of
-                // retian_btreeset()
+                // TODO when drain_filter() is no longer experimental, use it instead of
+                // retain_btreeset()
                 retain_btreeset(&mut self.blocked_by, |(_, c)| *c != car);
             }
         }
+
+        // If this intersection has uber-turns going through it, then we may need to wake up agents
+        // with a reserved uber-turn that're waiting at nearby intersections. They may have
+        // reserved their sequence of turns but then gotten stuck by somebody filling up a queue a
+        // few steps away.
+        for id in &self.state[&turn.parent].uber_turn_neighbors {
+            self.wakeup_waiting(now, *id, scheduler, map);
+        }
     }
 
     /// For deleting cars
@@ -561,6 +570,14 @@ impl IntersectionSimState {
                 }
                 (None, None) => {}
             }
+
+            // It's unlikely, but the player might create/destroy traffic signals close together and
+            // change the uber-turns that exist. To be safe, recalculate everywhere.
+            state.uber_turn_neighbors.clear();
+            if let Some(mut set) = map_model::IntersectionCluster::autodetect(state.id, map) {
+                set.remove(&state.id);
+                state.uber_turn_neighbors.extend(set);
+            }
         }
     }