Added a strategy cache for reusing previous round data

1 files changed, 30 insertions, 9 deletions

diff --git a/src/strategy.rs b/src/strategy.rs
index 8d2eea5..39bbe66 100644
--- a/src/strategy.rs
+++ b/src/strategy.rs
@@ -11,13 +11,30 @@ use rand;
 use rand::prelude::*;
 use arrayvec::ArrayVec;
 
-pub fn choose_move(state: &GameBoard, start_time: &PreciseTime, max_time: Duration) -> Command {
-    let mut root_node = Node {
-        state: state.clone(),
-        score_sum: ScoreSum::new(),
-        player_score_sums: [HashMap::new(), HashMap::new()],
-        unexplored: mcts_move_combo(state),
-        children: HashMap::new(),
+pub fn choose_move(state: &GameBoard, previous_root: Option<Node>, start_time: &PreciseTime, max_time: Duration) -> (Command, Node) {
+    let mut root_node = match previous_root {
+        None => Node {
+            state: state.clone(),
+            score_sum: ScoreSum::new(),
+            player_score_sums: [HashMap::new(), HashMap::new()],
+            unexplored: mcts_move_combo(state),
+            children: HashMap::new(),
+        },
+        Some(mut node) => {
+            node.children.drain()
+                .map(|(_k, n)| n)
+                .find(|n| n.state == *state)
+                .unwrap_or_else(|| {
+                    eprintln!("Previous round did not appear in the cache");
+                    Node {
+                        state: state.clone(),
+                        score_sum: ScoreSum::new(),
+                        player_score_sums: [HashMap::new(), HashMap::new()],
+                        unexplored: mcts_move_combo(state),
+                        children: HashMap::new(),
+                    }
+                })
+        }        
     };
 
     while start_time.to(PreciseTime::now()) < max_time {
@@ -34,10 +51,14 @@ pub fn choose_move(state: &GameBoard, start_time: &PreciseTime, max_time: Durati
         );
     }
 
-    best_player_move(&root_node)
+    let chosen_command = best_player_move(&root_node);
+
+    root_node.children.retain(|[c1, _], _| *c1 == chosen_command);
+        
+    (chosen_command, root_node)
 }
 
-struct Node {
+pub struct Node {
     state: GameBoard,
     score_sum: ScoreSum,
     player_score_sums: [HashMap<Command, ScoreSum>; 2],