boilerplate

Cargo.toml

@@ -6,4 +6,5 @@ edition = "2021"
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]
+bumpalo = { version = "3.9.1", features = ["collections"] }
 rand = "0.8.4"

src/basic_search.rs

@@ -1,4 +1,3 @@
-use crate::Node;
 use std::collections::VecDeque;
 
 struct Node<T> {
@@ -6,32 +5,38 @@ struct Node<T> {
     children: Vec<Node<T>>,
 }
 
-pub fn breadth_first_search<T: Eq>(tree: &Node<T>, searched: &T) -> bool {
+#[macro_export]
+macro_rules! tree {
+    ($first:expr $(, $($rest:expr),*)?) => {
+        $crate::basic_search::Node {
+            value: $first,
+            children: vec![$($($rest),*)?],
+        }
+    };
+}
+
+fn breadth_first_search<T: Eq>(tree: &Node<T>, searched: &T) -> bool {
     let mut candidates = VecDeque::new();
     candidates.push_back(tree);
 
-    loop {
-        if let Some(candidate) = candidates.pop_front() {
+    while let Some(candidate) = candidates.pop_front() {
         if candidate.value == *searched {
             return true;
         }
 
         candidates.extend(candidate.children.iter());
-        } else {
-            break;
-        }
     }
 
     false
 }
 
-pub fn depth_first_search<T: Eq>(tree: &Node<T>, searched: &T) -> bool {
+fn depth_first_search<T: Eq>(tree: &Node<T>, searched: &T) -> bool {
     if tree.value == *searched {
         return true;
     }
 
     for child in &tree.children {
-        if depth_first_search(&child, searched) {
+        if depth_first_search(child, searched) {
             return true;
         }
     }
@@ -41,7 +46,7 @@ pub fn depth_first_search<T: Eq>(tree: &Node<T>, searched: &T) -> bool {
 
 #[cfg(test)]
 mod tests {
-    use crate::basic_search::{self, Node};
+    use crate::basic_search;
     use crate::tree;
 
     #[test]

src/lib.rs

@@ -1,5 +1,8 @@
 #![allow(dead_code)]
 
+use bumpalo::collections::Vec;
+use bumpalo::Bump;
+
 use rand::Rng;
 
 mod basic_search;
@@ -7,38 +10,92 @@ mod basic_search;
 pub trait GameState {
     fn points(&self) -> i32;
 
-    fn next(&self) -> Box<dyn Iterator<Item = Self>>;
+    fn next(&self) -> &[Self]
+    where
+        Self: Sized;
+
+    fn is_finished(&self) -> bool;
 }
 
-impl GameState for i32 {
-    fn points(&self) -> i32 {
-        *self
+type Tree<'tree, S> = Node<'tree, S>;
+
+struct Node<'tree, S> {
+    state: S,
+    visited: u64,
+    won: u64,
+    parent: Option<&'tree Node<'tree, S>>,
+    children: Vec<'tree, Node<'tree, S>>,
 }
 
-    fn next(&self) -> Box<dyn Iterator<Item = Self>> {
-        let child_amount = rand::thread_rng().gen_range(0..10);
-        let mut i = 0;
-        Box::new(std::iter::from_fn(move || {
-            if i < child_amount {
-                Some(rand::random())
+impl<'tree, S: GameState> Node<'tree, S> {
+    fn new(state: S, alloc: &'tree Bump) -> Node<S> {
+        Node {
+            state,
+            visited: 0,
+            won: 0,
+            parent: None,
+            children: Vec::new_in(alloc),
+        }
+    }
+
+    fn random_child(&self) -> &Self {
+        &self.children[rand::thread_rng().gen_range(0..self.children.len())]
+    }
+
+    fn into_child_with_max_score(self) -> Self {
+        todo!()
+    }
+}
+
+mod mcts {
+    use crate::{GameState, Node};
+    use bumpalo::Bump;
+
+    const MAX_TRIES: u64 = 10000;
+
+    pub fn find_next_move<S: GameState>(current_state: S) -> S {
+        let alloc = Bump::new();
+
+        let root_node = Node::new(current_state, &alloc);
+
+        for _ in 0..MAX_TRIES {
+            let promising_node = select_promising_node(&root_node);
+
+            if !promising_node.state.is_finished() {
+                expand_node(promising_node);
+            }
+
+            let node_to_explore = if !node_to_explore.children.is_empty() {
+                promising_node.random_child()
             } else {
-                None
-            }
-        }))
-    }
-}
-
-#[macro_export]
-macro_rules! tree {
-    ($first:expr $(, $($rest:expr),*)?) => {
-        $crate::Node {
-            value: $first,
-            children: vec![$($($rest),*)?],
-        }
+                promising_node
             };
+
+            let playout_result = simulate_random_playout(node_to_explore);
+            back_propagation(node_to_explore, playout_result);
         }
 
-mod mcts {}
+        let winner_node = root_node.into_child_with_max_score();
+
+        winner_node.state
+    }
+
+    fn select_promising_node<'tree, S>(node: &'tree Node<'_, S>) -> &'tree Node<'tree, S> {
+        todo!()
+    }
+
+    fn expand_node<S>(node: &Node<S>) {
+        todo!()
+    }
+
+    fn simulate_random_playout<S>(node: &Node<'_, S>) -> u64 {
+        todo!()
+    }
+
+    fn back_propagation<S>(node: &Node<'_, S>, playout_result: u64) {
+        todo!()
+    }
+}
 
 #[cfg(test)]
 mod test {