From: Mikko Rasa <tdb@tdb.fi>
Date: Sun, 30 Mar 2014 13:43:54 +0000 (+0300)
Subject: Make deadlock detection more robust
X-Git-Url: http://git.tdb.fi/?a=commitdiff_plain;h=932c76bc0358eeaf1c18cc950201226262d0df17;p=r2c2.git

Make deadlock detection more robust

Deadlock cycles involving more than two trains can now be detected.
---

diff --git a/source/libr2c2/trainrouteplanner.cpp b/source/libr2c2/trainrouteplanner.cpp
index 45e83e2..e8b5d90 100644
--- a/source/libr2c2/trainrouteplanner.cpp
+++ b/source/libr2c2/trainrouteplanner.cpp
@@ -336,17 +336,24 @@ bool TrainRoutePlanner::RoutingStep::update_states()
 
 bool TrainRoutePlanner::RoutingStep::check_deadlocks() const
 {
-	for(unsigned i=0; i<trains.size(); ++i)
+	for(vector<TrainRoutingState>::const_iterator i=trains.begin(); i!=trains.end(); ++i)
 	{
-		const TrainRoutingState &train = trains[i];
-		if(train.state!=BLOCKED)
+		if(i->state!=BLOCKED)
 			continue;
 
-		if(train.blocked_by<0)
+		if(i->blocked_by<0)
 			return true;
 
-		if(trains[train.blocked_by].blocked_by==static_cast<int>(i))
-			return true;
+		int slow = i->blocked_by;
+		int fast = trains[slow].blocked_by;
+		while(fast>=0 && trains[fast].blocked_by>=0)
+		{
+			if(fast==slow)
+				return true;
+
+			slow = trains[slow].blocked_by;
+			fast = trains[trains[fast].blocked_by].blocked_by;
+		}
 	}
 
 	return false;