use faster rng

battlesnake/benches/simulation.rs

@@ -1,15 +1,16 @@
 use std::sync::{
-    atomic::{AtomicU32, Ordering},
     Arc,
+    atomic::{AtomicU32, Ordering},
 };
 
-use criterion::{black_box, criterion_group, criterion_main, Bencher, BenchmarkId, Criterion};
+use criterion::{Bencher, BenchmarkId, Criterion, black_box, criterion_group, criterion_main};
 
 use battlesnake::types::{
+    Coord,
     simulation::Board,
     wire::{Battlesnake, Board as WireBoard, Game, Request, RoyaleSettings, Ruleset, Settings},
-    Coord,
 };
+use rand::{SeedableRng, rngs::SmallRng};
 
 fn create_start_snake(coord: Coord) -> Battlesnake {
     let id: Arc<str> = format!("{coord:?}").into();
@@ -74,7 +75,7 @@ fn standard(c: &mut Criterion) {
     let benchmark = |b: &mut Bencher, board: &Board| {
         b.iter(|| {
             let mut board = board.clone();
-            let turn = board.simulate_random(|board| {
+            let turn = board.simulate_random(&mut SmallRng::from_os_rng(), |board| {
                 if board.num_snakes() <= 1 {
                     Some(board.turn())
                 } else {
@@ -151,7 +152,7 @@ fn constrictor(c: &mut Criterion) {
     let benchmark = |b: &mut Bencher, board: &Board| {
         b.iter(|| {
             let mut board = board.clone();
-            let turn = board.simulate_random(|board| {
+            let turn = board.simulate_random(&mut SmallRng::from_os_rng(), |board| {
                 if board.num_snakes() <= 1 {
                     Some(board.turn())
                 } else {

battlesnake/src/main.rs

@@ -13,7 +13,7 @@ use battlesnake::types::{
 };
 use float_ord::FloatOrd;
 use log::{debug, error, info, trace, warn};
-use rand::{prelude::*, rng};
+use rand::prelude::*;
 use serde::Serialize;
 use tokio::{
     net::TcpListener,
@@ -89,6 +89,7 @@ async fn get_move(request: Json<Request>) -> response::Json<Response> {
     info!("valid actions: {actions:?}");
 
     tokio::task::spawn_blocking(move || {
+        let mut rng = SmallRng::from_os_rng();
         if start.elapsed() > Duration::from_millis(10) {
             error!(
                 "The calculation started late ({}ms)",
@@ -129,23 +130,22 @@ async fn get_move(request: Json<Request>) -> response::Json<Response> {
             .map(|id| MctsManager::new(u8::try_from(id).unwrap()))
             .collect();
         let c = f32::sqrt(2.0);
+        let mut mcts_actions = Vec::new();
         while start.elapsed() < timeout * 4 / 5 {
             let mut board = board.clone();
             while end_condition(&board).is_none() {
-                let actions: Vec<_> = mcts_managers
-                    .iter_mut()
-                    .filter_map(|mcts_manager| {
-                        mcts_manager
-                            .next_action(&board, c)
-                            .map(|action| (mcts_manager.snake, action))
-                    })
-                    .collect();
-                board.next_turn(&actions);
-                if actions.is_empty() {
+                mcts_actions.clear();
+                mcts_actions.extend(mcts_managers.iter_mut().filter_map(|mcts_manager| {
+                    mcts_manager
+                        .next_action(&board, c, &mut rng)
+                        .map(|action| (mcts_manager.snake, action))
+                }));
+                board.next_turn(&mcts_actions, &mut rng);
+                if mcts_actions.is_empty() {
                     break;
                 }
             }
-            board.simulate_random(end_condition);
+            board.simulate_random(&mut rng, end_condition);
             for mcts_manager in &mut mcts_managers {
                 let id = mcts_manager.snake;
                 let score = score_fn(&board, id);
@@ -273,7 +273,7 @@ impl MctsManager {
         self.expanded = false;
     }
 
-    fn next_action(&mut self, board: &Board, c: f32) -> Option<Direction> {
+    fn next_action(&mut self, board: &Board, c: f32, rng: &mut impl RngCore) -> Option<Direction> {
         if self.expanded {
             return None;
         }
@@ -294,11 +294,7 @@ impl MctsManager {
             .collect();
         trace!("got actions: {ucts:?}");
         if ucts.iter().any(|(_, uct)| uct.is_none()) {
-            let action = ucts
-                .iter()
-                .filter(|(_, uct)| uct.is_none())
-                .choose(&mut rng())?
-                .0;
+            let action = ucts.iter().filter(|(_, uct)| uct.is_none()).choose(rng)?.0;
             self.expanded = true;
             current.next[usize::from(action)].replace(ActionInfo::new());
             self.actions.push(action);

battlesnake/src/types/simulation.rs

@@ -8,7 +8,7 @@ use std::{
 
 use bitvec::prelude::*;
 use log::{error, warn};
-use rand::{prelude::*, rng};
+use rand::prelude::*;
 
 use super::{Coord, Direction, wire::Request};
 
@@ -256,43 +256,50 @@ impl Board {
     }
 
     #[must_use]
-    pub fn random_action(&self, id: u8) -> Direction {
+    pub fn random_action(&self, id: u8, rng: &mut impl RngCore) -> Direction {
         let Some(index) = self.id_to_index(id) else {
             return Direction::Up;
         };
         self.valid_actions_index(index)
-            .choose(&mut rng())
+            .choose(rng)
             .unwrap_or(Direction::Up)
     }
 
-    pub fn random_actions(&self) -> impl Iterator<Item = (u8, Direction)> + use<'_> {
+    pub fn random_actions<'a, R: RngCore>(
+        &self,
+        rng: &'a mut R,
+    ) -> impl Iterator<Item = (u8, Direction)> + use<'_, 'a, R> {
         (0..self.snakes.len()).map(|index| {
             (
                 self.snakes[index].id,
                 self.valid_actions_index(index)
-                    .choose(&mut rng())
+                    .choose(rng)
                     .unwrap_or(Direction::Up),
             )
         })
     }
 
-    pub fn simulate_random<T>(&mut self, stop: impl Fn(&Self) -> Option<T>) -> T {
+    pub fn simulate_random<T>(
+        &mut self,
+        rng: &mut impl RngCore,
+        stop: impl Fn(&Self) -> Option<T>,
+    ) -> T {
         loop {
             if let Some(score) = stop(self) {
                 break score;
             }
-            self.next_turn(&[]);
+            self.next_turn(&[], rng);
         }
     }
 
-    pub fn next_turn(&mut self, actions: &[(u8, Direction)]) {
-        self.move_standard(actions);
+    pub fn next_turn(&mut self, actions: &[(u8, Direction)], rng: &mut impl RngCore) {
+        self.move_standard(actions, rng);
         self.starvation_standard();
         self.hazard_damage_standard();
         self.feed_snakes_standard();
         self.eliminate_snake_standard();
         self.update_free_map();
-        self.spawn_food();
+        self.spawn_food(rng);
         self.turn += 1;
     }
 
@@ -306,13 +313,13 @@ impl Board {
             .filter(move |direction| self.is_free(head.wrapping_apply(*direction)))
     }
 
-    fn move_standard(&mut self, actions: &[(u8, Direction)]) {
+    fn move_standard(&mut self, actions: &[(u8, Direction)], rng: &mut impl RngCore) {
         for i in 0..self.snakes.len() {
             let snake = &self.snakes[i];
             let action = actions.iter().find(|(id, _)| *id == snake.id).map_or_else(
                 || {
                     self.valid_actions_index(i)
-                        .choose(&mut rng())
+                        .choose(rng)
                         .unwrap_or(Direction::Up)
                 },
                 |(_, action)| *action,
@@ -445,15 +452,15 @@ impl Board {
         }
     }
 
-    fn spawn_food(&mut self) {
-        let food_needed = self.check_food_needing_placement();
+    fn spawn_food(&mut self, rng: &mut impl RngCore) {
+        let food_needed = self.check_food_needing_placement(rng);
 
         if food_needed > 0 {
-            self.place_food_randomly(food_needed);
+            self.place_food_randomly(food_needed, rng);
         }
     }
 
-    fn check_food_needing_placement(&self) -> u16 {
+    fn check_food_needing_placement(&self, rng: &mut impl RngCore) -> u16 {
         let min_food = self.min_food;
         let food_spawn_chance = self.food_spawn_chance;
         let num_current_food = u16::try_from(self.food.count_ones()).unwrap_or(u16::MAX);
@@ -461,14 +468,14 @@ impl Board {
         if num_current_food < min_food {
             return min_food - num_current_food;
         }
-        if food_spawn_chance > 0 && (100 - rng().random_range(0..100)) < food_spawn_chance {
+        if food_spawn_chance > 0 && (100 - rng.random_range(0..100)) < food_spawn_chance {
             return 1;
         }
 
         0
     }
 
-    fn place_food_randomly(&mut self, amount: u16) {
+    fn place_food_randomly(&mut self, amount: u16, rng: &mut impl RngCore) {
         let tails: Vec<_> = self
             .snakes
             .iter()
@@ -495,7 +502,7 @@ impl Board {
             .filter(|i| !tails.contains(i))
             .filter(|i| !possible_moves.contains(i));
 
-        for food_spot in unoccupied_points.choose_multiple(&mut rng(), usize::from(amount)) {
+        for food_spot in unoccupied_points.choose_multiple(rng, usize::from(amount)) {
             self.food.set(food_spot, true);
         }
     }