Cargo.lock

@@ -2,12 +2,6 @@
 # It is not intended for manual editing.
 version = 4
 
-[[package]]
-name = "bitflags"
-version = "2.9.1"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "1b8e56985ec62d17e9c1001dc89c88ecd7dc08e47eba5ec7c29c7b5eeecde967"
-
 [[package]]
 name = "cfg-if"
 version = "1.0.1"
@@ -16,13 +10,12 @@ checksum = "9555578bc9e57714c812a1f84e4fc5b4d21fcb063490c624de019f7464c91268"
 
 [[package]]
 name = "getrandom"
-version = "0.3.3"
+version = "0.2.16"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "26145e563e54f2cadc477553f1ec5ee650b00862f0a58bcd12cbdc5f0ea2d2f4"
+checksum = "335ff9f135e4384c8150d6f27c6daed433577f86b4750418338c01a1a2528592"
 dependencies = [
  "cfg-if",
  "libc",
- "r-efi",
  "wasi",
 ]
 
@@ -59,27 +52,22 @@ dependencies = [
  "proc-macro2",
 ]
 
-[[package]]
-name = "r-efi"
-version = "5.3.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "69cdb34c158ceb288df11e18b4bd39de994f6657d83847bdffdbd7f346754b0f"
-
 [[package]]
 name = "rand"
-version = "0.9.1"
+version = "0.8.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "9fbfd9d094a40bf3ae768db9361049ace4c0e04a4fd6b359518bd7b73a73dd97"
+checksum = "34af8d1a0e25924bc5b7c43c079c942339d8f0a8b57c39049bef581b46327404"
 dependencies = [
+ "libc",
  "rand_chacha",
  "rand_core",
 ]
 
 [[package]]
 name = "rand_chacha"
-version = "0.9.0"
+version = "0.3.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "d3022b5f1df60f26e1ffddd6c66e8aa15de382ae63b3a0c1bfc0e4d3e3f325cb"
+checksum = "e6c10a63a0fa32252be49d21e7709d4d4baf8d231c2dbce1eaa8141b9b127d88"
 dependencies = [
  "ppv-lite86",
  "rand_core",
@@ -87,9 +75,9 @@ dependencies = [
 
 [[package]]
 name = "rand_core"
-version = "0.9.3"
+version = "0.6.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "99d9a13982dcf210057a8a78572b2217b667c3beacbf3a0d8b454f6f82837d38"
+checksum = "ec0be4795e2f6a28069bec0b5ff3e2ac9bafc99e6a9a7dc3547996c5c816922c"
 dependencies = [
  "getrandom",
 ]
@@ -141,21 +129,9 @@ checksum = "5a5f39404a5da50712a4c1eecf25e90dd62b613502b7e925fd4e4d19b5c96512"
 
 [[package]]
 name = "wasi"
-version = "0.14.2+wasi-0.2.4"
+version = "0.11.1+wasi-snapshot-preview1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "9683f9a5a998d873c0d21fcbe3c083009670149a8fab228644b8bd36b2c48cb3"
+checksum = "ccf3ec651a847eb01de73ccad15eb7d99f80485de043efb2f370cd654f4ea44b"
-dependencies = [
- "wit-bindgen-rt",
-]
-
-[[package]]
-name = "wit-bindgen-rt"
-version = "0.39.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "6f42320e61fe2cfd34354ecb597f86f413484a798ba44a8ca1165c58d42da6c1"
-dependencies = [
- "bitflags",
-]
 
 [[package]]
 name = "zerocopy"

Cargo.toml

@@ -12,5 +12,5 @@ categories = ["algorithms", "data-structures"]
 
 
 [dependencies]
-rand = "~0.9"
+rand = "~0.8"
 thiserror = "~2.0"

examples/auto_tic_tac_toe.rs

@@ -40,7 +40,6 @@ fn main() {
         // Find the best move
         match mcts.search() {
             Ok(action) => {
-                mcts.print_tree();
                 println!(
                     "AI chooses: {} (row {}, col {})",
                     action.index,

src/mcts.rs

@@ -6,8 +6,7 @@ use crate::policy::simulation::simulate_reward;
 use crate::state::GameState;
 use crate::tree::arena::Arena;
 use crate::tree::node::{Node, RewardVal};
-use crate::tree::print_tree;
+use rand::prelude::SliceRandom;
-use rand::prelude::IndexedRandom;
 use std::collections::HashMap;
 use std::time::Instant;
 
@@ -75,7 +74,7 @@ impl<'conf, S: GameState + std::fmt::Debug> MCTS<'conf, S> {
         if !selected_node.state.is_terminal() {
             self.expand(selected_id);
             let children: &Vec<usize> = &self.arena.get_node(selected_id).children;
-            let random_child: usize = *children.choose(&mut rand::rng()).unwrap();
+            let random_child: usize = *children.choose(&mut rand::thread_rng()).unwrap();
             selected_id = random_child;
         }
         let rewards = self.simulate(selected_id);
@@ -131,10 +130,6 @@ impl<'conf, S: GameState + std::fmt::Debug> MCTS<'conf, S> {
             None => Err(MCTSError::NoBestAction),
         }
     }
-
-    pub fn print_tree(&self) {
-        print_tree(self.root_id, &self.arena)
-    }
 }
 
 /// Errors returned by the MCTS algorithm

src/policy/backprop/mod.rs

@@ -69,14 +69,18 @@ fn standard_backprop<S: GameState>(
     let mut current_id: usize = node_id;
     loop {
         let node = arena.get_node_mut(current_id);
-        node.increment_visits();
+        let player = node.state.get_current_player().clone();
-        for (player, reward) in rewards.iter() {
+        match rewards.get(&player) {
-            node.record_player_reward(player.clone(), *reward);
+            Some(reward) => {
-        }
+                node.increment_visits();
-        if let Some(parent_id) = node.parent {
+                node.record_player_reward(player, *reward);
-            current_id = parent_id;
+                if let Some(parent_id) = node.parent {
-        } else {
+                    current_id = parent_id;
-            break;
+                } else {
+                    break;
+                }
+            }
+            None => (),
         }
     }
 }
@@ -90,14 +94,19 @@ fn weighted_backprop<S: GameState>(
     let mut current_id: usize = node_id;
     loop {
         let node = arena.get_node_mut(current_id);
+        let player = node.state.get_current_player().clone();
         let weight = weight_for_depth(depth_factor, node.depth);
-        for (player, reward) in rewards.iter() {
+        match rewards.get(&player) {
-            node.record_player_reward(player.clone(), (*reward) * weight);
+            Some(reward) => {
-        }
+                node.increment_visits();
-        if let Some(parent_id) = node.parent {
+                node.record_player_reward(player, (*reward) * weight);
-            current_id = parent_id;
+                if let Some(parent_id) = node.parent {
-        } else {
+                    current_id = parent_id;
-            break;
+                } else {
+                    break;
+                }
+            }
+            None => (),
         }
     }
 }

src/policy/simulation/random.rs

@@ -4,14 +4,14 @@
 
 use crate::state::GameState;
 use crate::tree::node::{Node, RewardVal};
-use rand::prelude::IndexedRandom;
+use rand::prelude::SliceRandom;
 use std::collections::HashMap;
 
 pub fn simulate<S: GameState>(node: &Node<S>) -> HashMap<S::Player, RewardVal> {
     let mut state: S = node.state.clone();
     while !state.is_terminal() {
         let legal_actions = state.get_legal_actions();
-        let action = legal_actions.choose(&mut rand::rng()).unwrap();
+        let action = legal_actions.choose(&mut rand::thread_rng()).unwrap();
         state = state.state_after_action(&action);
     }
     state.rewards_for_players()

src/state.rs

@@ -7,7 +7,7 @@ use std::hash::Hash;
 ///
 /// When leveraging MCTS for your game, you must implement this trait to provide
 /// the specifics for your game.
-pub trait GameState: Clone + Debug {
+pub trait GameState: Clone {
     /// The type of actions that can be taken in the game
     type Action: Action;
 

src/tree/mod.rs

@@ -1,27 +1,2 @@
 pub mod arena;
 pub mod node;
-
-use crate::state::GameState;
-use crate::tree::arena::Arena;
-use crate::tree::node::Node;
-
-pub fn print_tree<S: GameState>(node_id: usize, arena: &Arena<S>) {
-    let mut to_print: Vec<usize> = Vec::new();
-    to_print.push(node_id);
-    while let Some(node_id) = to_print.pop() {
-        let node: &Node<S> = arena.get_node(node_id);
-        if node.depth > 0 {
-            for _ in 0..node.depth - 1 {
-                print!("|  ")
-            }
-            print!("|- ");
-        }
-        println!(
-            "{:?} a:{:?} v:{}  {:?}",
-            node_id, node.action, node.visits, node.player_view
-        );
-        for child_id in node.children.iter().rev() {
-            to_print.push(*child_id);
-        }
-    }
-}

src/tree/node.rs

@@ -1,4 +1,5 @@
 use std::collections::HashMap;
+use std::fmt::Debug;
 
 use crate::state::GameState;
 
@@ -14,7 +15,7 @@ pub type RewardVal = f64;
 ///
 /// This class is not thread safe, as the library does not provide for parallel
 /// search.
-#[derive(std::fmt::Debug)]
+#[derive(Debug)]
 pub struct Node<S: GameState> {
     /// The game state at the given node, after `action`
     pub state: S,
@@ -29,7 +30,7 @@ pub struct Node<S: GameState> {
     pub visits: u64,
 
     /// The player's evaluation of the node
-    pub player_view: HashMap<S::Player, PlayerRewardView>,
+    pub player_view: HashMap<S::Player, PlayerNodeView>,
 
     /// The depth of the node in the tree, this is 0 for the root node
     pub depth: usize,
@@ -81,7 +82,10 @@ impl<S: GameState> Node<S> {
     }
 
     pub fn record_player_reward(&mut self, player: S::Player, reward: RewardVal) {
-        let pv = self.player_view.entry(player).or_default();
+        let pv = self
+            .player_view
+            .entry(player)
+            .or_insert(PlayerNodeView::default());
         pv.rewards.push(reward);
         pv.reward_sum += reward;
         pv.reward_average = pv.reward_sum / pv.rewards.len() as f64;
@@ -91,7 +95,8 @@ impl<S: GameState> Node<S> {
 /// A player's specific perspective of a node's value
 ///
 /// Each player has their own idea of the value of a node.
-pub struct PlayerRewardView {
+#[derive(Debug)]
+pub struct PlayerNodeView {
     /// The total reward from simulations through this node
     pub reward_sum: RewardVal,
 
@@ -102,19 +107,12 @@ pub struct PlayerRewardView {
     pub rewards: Vec<RewardVal>,
 }
 
-impl Default for PlayerRewardView {
+impl Default for PlayerNodeView {
     fn default() -> Self {
-        PlayerRewardView {
+        PlayerNodeView {
             reward_sum: 0.0,
             reward_average: 0.0,
             rewards: Vec::new(),
         }
     }
 }
-
-impl std::fmt::Debug for PlayerRewardView {
-    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-        write!(f, "{{sum={} avg={}}}", self.reward_sum, self.reward_average)?;
-        Ok(())
-    }
-}