reduce copies

src/complexagent.rs

@@ -195,12 +195,12 @@ impl FutureMoves {
             .find_map(|(idx, node)| {
                 (node.parent == self.current_root && node.i == i && node.j == j).then_some(idx)
             })
-            .inspect(|&root| {
+            .is_some_and(|root| {
                 self.current_root = Some(root);
                 self.current_depth = self.max_depth - self.depth_of(root);
                 self.prune_unrelated();
+                true
             })
-            .is_some()
     }
 
     fn prune_unrelated(&mut self) {
@@ -216,28 +216,40 @@ impl FutureMoves {
             stack.extend(self.arena[idx].children.iter());
         }
 
-        let mut new_arena = Vec::with_capacity(self.arena.len());
         let mut index_map = vec![None; self.arena.len()];
 
         // PERF: reverse iterator to avoid unneeded `memcpy`s when deconstructing the Arena
-        for (old_idx, keep) in retain.into_iter().enumerate().rev() {
+        self.arena = retain
-            let mut node = self.arena.remove(old_idx);
+            .into_iter()
-            if keep {
+            .enumerate()
-                index_map[old_idx] = Some(new_arena.len());
+            .rev()
+            .enumerate()
+            .flat_map(|(new_idx, (old_idx, keep))| {
+                let node = self.arena.remove(old_idx);
+                if keep {
+                    Some((new_idx, (old_idx, node)))
+                } else {
+                    None
+                }
+            })
+            .map(|(new_idx, (old_idx, mut node))| {
+                index_map[old_idx] = Some(new_idx);
 
                 node.parent = node.parent.and_then(|p| index_map[p]);
 
-                node.children = node
+                node.children.retain_mut(|c| {
-                    .children
+                    if let Some(new_c) = index_map[*c] {
-                    .into_iter()
+                        *c = new_c;
-                    .filter_map(|c| index_map[c])
+                        true
-                    .collect();
+                    } else {
+                        false
+                    }
+                });
 
-                new_arena.push(node);
+                node
-            }
+            })
-        }
+            .collect();
 
-        self.arena = new_arena;
         self.current_root = index_map[root];
     }
 }
@@ -249,7 +261,7 @@ pub struct ComplexAgent {
 
 impl ComplexAgent {
     pub const fn new(color: Piece) -> Self {
-        const MAX_DEPTH: usize = 10;
+        const MAX_DEPTH: usize = 8;
         const MAX_ARENA: usize = 20_000_000;
         Self {
             color,