Remove unnecessary changing of predecessor-set.

README.md

@@ -71,7 +71,7 @@ When done, remove the image:
     - It checks if some successor of the green node is in the winning set. 
     - If that is the case, the green node is added to the winning set, and removed from the nodes being iterated on.  
     - Any time a node is added to the winning set, any red nodes that are a predecessor of this newly added node have their counter reduced by 1.
-    - If the counter of a red node reaches 0, it is added to the winning set and removed from the predecessor-set of the added node.
+    - If the counter of a red node reaches 0, it is added to the winning set.
     - The loop runs until no new nodes are added in the `pre`-step.
 
 # Libraries used

src/arena.rs

@@ -11,20 +11,18 @@ fn insert_node(
     let mut to_insert = vec![node];
     while let Some(node) = to_insert.pop() {
         additional_winning.insert(node.clone());
-        let predecessors = pred.entry(node);
-        predecessors.and_modify(|predecessors| {
-            let mut changed_predecessors = HashSet::new();
-            for predecessor in predecessors.iter() {
-                let counter = predecessor.counter.take() - 1;
-                if counter == 0 {
-                    to_insert.push(predecessor.id.clone());
-                } else {
-                    predecessor.counter.replace(counter);
-                    changed_predecessors.insert(predecessor.clone());
+        if let Some(predecessors) = pred.get(&node) {
+            for predecessor in predecessors {
+                let mut counter = predecessor.counter.borrow_mut();
+                if *counter >= 1 {
+                    // This is the last successor needed for the red node to get added
+                    if *counter == 1 {
+                        to_insert.push(predecessor.id.clone());
+                    }
+                    *counter -= 1;
                 }
             }
-            *predecessors = changed_predecessors
-        });
+        }
     }
 }
 
@@ -70,6 +68,7 @@ pub fn winning_positions(
             "[prestep] Winning positions after adding final positions: {:?}",
             winning_positions
         );
+        debug!("[prestep] Predecessors: {:#?}", pred);
     }
     // Remove green nodes that have already been added to winners due to being final positions
     greens = greens
@@ -89,6 +88,7 @@ pub fn winning_positions(
         if additional_winnings.is_empty() {
             return winning_positions;
         }
+        debug!("[iter] Predecessors: {:#?}", pred);
         greens = changed_greens;
         winning_positions.extend(additional_winnings);
     }