add Move::lazy_children

src/complexagent.rs

@@ -29,6 +29,8 @@ struct Move {
     value: i64,
 
     color: Piece,
+
+    lazy_children: bool,
 }
 
 impl Move {
@@ -82,25 +84,39 @@ impl FutureMoves {
         }
     }
 
+    const LAZY_EXPIRE: usize = 6;
+
     /// Generate children for all children of `nodes`
     fn extend_layers(&mut self) {
         let mut next_nodes: Vec<usize> = (0..self.arena.len())
-            .filter(|&idx| self.arena[idx].children.is_empty())
+            // we want to select all nodes that don't have children, or are lazy (need to maybe be regenerated)
+            .filter(|&idx| self.arena[idx].children.is_empty() || self.arena[idx].lazy_children)
             .filter(|&idx| self.is_connected_to_root(idx)) // put here so this will not extend needlessly before prunes
             .collect();
 
-        for _ in self.current_depth..=self.max_depth {
-            // TODO! use `i` in order to prune along-the-way
-            // i.e, every 4 moves of color `self.agent_color`, do a pruning step,
-            // only keeping the top [`Move`]
-
+        for i in self.current_depth..=self.max_depth {
             next_nodes = next_nodes
                 .into_iter()
                 .progress_with_style(
-                    ProgressStyle::with_template("Generating children: ({pos}/{len}) {per_sec}")
-                        .unwrap(),
+                    ProgressStyle::with_template(&format!(
+                        "Generating children (depth: {}/{}): ({{pos}}/{{len}}) {{per_sec}}",
+                        i, self.max_depth
+                    ))
+                    .unwrap(),
                 )
-                .flat_map(|node_idx| self.generate_children(node_idx))
+                .flat_map(|node_idx| {
+                    self.generate_children(
+                        node_idx,
+                        if self.arena[node_idx].lazy_children
+                            && self.depth_of(node_idx) - 1 < Self::LAZY_EXPIRE
+                        {
+                            false
+                        } else {
+                            // this is a non-lazy_children child, should it be lazy?
+                            i > Self::LAZY_EXPIRE
+                        },
+                    )
+                })
                 .flatten()
                 .collect();
         }
@@ -124,17 +140,23 @@ impl FutureMoves {
     }
 
     /// Creates children for a parent (`parent`), returns an iterator it's children's indexes
-    fn generate_children(&mut self, parent_idx: usize) -> Option<impl Iterator<Item = usize>> {
+    fn generate_children(
+        &mut self,
+        parent_idx: usize,
+        lazy_children: bool,
+    ) -> Option<impl Iterator<Item = usize>> {
         // early-exit if a winner for the parent already exists
         if self.arena[parent_idx].winner != Winner::None {
             return None;
         }
 
+        let new_color = !self.arena[parent_idx].color;
+        let parent_lazy = self.arena[parent_idx].lazy_children;
         let mut new: Vec<Move> =
             // use [`Board::all_positions`] here instead of [`Board::possible_moves`]
             // because we use [`Board::what_if`] later and we want to reduce calls to [`Board::propegate_from_dry`]
             Board::all_positions()
-                .flat_map(|(i, j)| self.arena[parent_idx].board.what_if(i, j, !self.arena[parent_idx].color).map(|x| (i, j, x)))
+                .flat_map(|(i, j)| self.arena[parent_idx].board.what_if(i, j, new_color).map(|x| (i, j, x)))
                 .map(|(i, j, new_board)| Move {
                     i,
                     j,
@@ -143,22 +165,37 @@ impl FutureMoves {
                     parent: Some(parent_idx),
                     children: Vec::new(),
                     value: 0,
-                    color: !self.arena[parent_idx].color
+                    color: new_color,
+                    lazy_children,
                 }).collect();
 
+        // negative, because we want the max value to be at the first index
+        new.sort_by_key(|x| -x.compute_self_value(self.agent_color));
+
         // keep the TOP_K children `self.agent_color`-color moves
         const TOP_K_CHILDREN: usize = 1;
 
         // we want to keep only the best move of the agent
-        if !self.arena[parent_idx].color == self.agent_color && new.len() > TOP_K_CHILDREN {
+        if lazy_children && new_color == self.agent_color && new.len() > TOP_K_CHILDREN {
             // TODO! Move this to `extend_layers` so we can prune based on recursive [`Move`] value
-            // negative, because we want the max value to be at the first index
-            new.sort_by_key(|x| -x.compute_self_value(self.agent_color));
+
             new.drain(TOP_K_CHILDREN..);
         }
 
         let start_idx = self.arena.len();
-        self.arena.extend(new);
+        if parent_lazy && !lazy_children {
+            // this move's children are being regenerated after lazy child expiration, don't append first node
+            if new.len() > 1 {
+                self.arena.extend(new.drain(1..));
+            } else {
+                // nothing will be appended
+                // even though it was sorted the first time around
+                // there's still no more than one element (which is already in the arena)
+                return None;
+            }
+        } else {
+            self.arena.extend(new);
+        }
         let new_indices = start_idx..self.arena.len();
 
         self.arena[parent_idx].children.extend(new_indices.clone());
@@ -250,6 +287,7 @@ impl FutureMoves {
                 children: Vec::new(),
                 value: 0,
                 color: !self.agent_color,
+                lazy_children: false,
             });
             self.update_root_idx(0);
         }
@@ -348,7 +386,7 @@ pub struct ComplexAgent {
 
 impl ComplexAgent {
     pub const fn new(color: Piece) -> Self {
-        const MAX_DEPTH: usize = 15;
+        const MAX_DEPTH: usize = 10;
         Self {
             color,
             future_moves: FutureMoves::new(color, MAX_DEPTH),