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use crate::command::{Command, Action};
use crate::game::{GameBoard, SimulationOutcome};
use std::cmp;
use std::collections::HashMap;
use std::ops::*;
use time::{Duration, PreciseTime};
use rand;
use rand::prelude::*;
use arrayvec::ArrayVec;
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 {
let _ = mcts(&mut root_node);
}
eprintln!("Number of simulations: {}", root_node.score_sum.visit_count);
for (command, score_sum) in &root_node.player_score_sums[0] {
eprintln!(
"{} = {} ({} visits)",
command,
score_sum.avg().val,
score_sum.visit_count
);
}
let chosen_command = best_player_move(&root_node);
root_node.children.retain(|[c1, _], _| *c1 == chosen_command);
(chosen_command, root_node)
}
pub struct Node {
state: GameBoard,
score_sum: ScoreSum,
player_score_sums: [HashMap<Command, ScoreSum>; 2],
unexplored: Vec<[Command; 2]>,
children: HashMap<[Command; 2], Node>,
}
#[derive(Clone, Copy, Debug, PartialEq, PartialOrd)]
struct Score {
val: f32,
}
impl AddAssign for Score {
fn add_assign(&mut self, other: Self) {
self.val = self.val + other.val;
}
}
impl Div<u32> for Score {
type Output = Self;
fn div(self, other: u32) -> Self {
Score {
val: self.val / other as f32,
}
}
}
impl cmp::Eq for Score {}
impl cmp::Ord for Score {
fn cmp(&self, other: &Score) -> cmp::Ordering {
self.val
.partial_cmp(&other.val)
.unwrap_or(cmp::Ordering::Equal)
}
}
struct ScoreSum {
sum: Score,
visit_count: u32,
}
impl ScoreSum {
fn new() -> ScoreSum {
ScoreSum {
sum: Score { val: 0. },
visit_count: 0,
}
}
fn with_initial(score: Score) -> ScoreSum {
ScoreSum {
sum: score,
visit_count: 1,
}
}
fn avg(&self) -> Score {
self.sum / self.visit_count
}
}
impl AddAssign<Score> for ScoreSum {
fn add_assign(&mut self, other: Score) {
self.sum += other;
self.visit_count = self.visit_count.saturating_add(1);
}
}
fn mcts(node: &mut Node) -> Score {
if node.state.outcome != SimulationOutcome::Continue {
score(&node.state)
} else if let Some(commands) = node.unexplored.pop() {
let mut new_state = node.state.clone();
new_state.simulate(commands);
let score = rollout(&new_state);
let unexplored = if new_state.outcome == SimulationOutcome::Continue {
mcts_move_combo(&new_state)
} else {
Vec::new()
};
let new_node = Node {
state: new_state,
score_sum: ScoreSum::with_initial(score),
player_score_sums: [HashMap::new(), HashMap::new()],
unexplored,
children: HashMap::new(),
};
node.children.insert(commands, new_node);
update(node, commands, score);
score
} else {
let commands = choose_existing(node);
let score = mcts(
node.children
.get_mut(&commands)
.expect("The existing node hasn't been tried yet"),
);
update(node, commands, score);
score
}
}
fn mcts_move_combo(state: &GameBoard) -> Vec<[Command; 2]> {
let player_moves = valid_moves(state, 0);
let opponent_moves = valid_moves(state, 1);
debug_assert!(player_moves.len() > 0, "No player moves");
debug_assert!(player_moves.len() > 0, "No opponent moves");
let mut result = Vec::with_capacity(player_moves.len() * opponent_moves.len());
for p in &player_moves {
for o in &opponent_moves {
result.push([*p, *o]);
}
}
result
}
fn best_player_move(node: &Node) -> Command {
node.player_score_sums[0]
.iter()
.max_by_key(|(_command, score_sum)| score_sum.avg())
.map(|(command, _score_sum)| *command)
.unwrap_or_else(|| Command::new(Action::DoNothing))
}
fn score(state: &GameBoard) -> Score {
Score {
val: match state.outcome {
SimulationOutcome::PlayerWon(0) => 500.,
SimulationOutcome::PlayerWon(1) => -500.,
_ => (state.players[0].score() - state.players[1].score()) as f32,
}
}
}
fn rollout(state: &GameBoard) -> Score {
let mut s = state.clone();
let mut rng = rand::thread_rng();
while s.outcome == SimulationOutcome::Continue {
let player_moves = rollout_moves(&s, 0);
let opponent_moves = rollout_moves(&s, 1);
s.simulate([
player_moves
.choose(&mut rng)
.cloned()
.unwrap_or_else(|| Command::new(Action::DoNothing)),
opponent_moves
.choose(&mut rng)
.cloned()
.unwrap_or_else(|| Command::new(Action::DoNothing)),
]);
}
score(&s)
}
fn choose_existing(node: &Node) -> [Command; 2] {
[choose_one_existing(node, 0), choose_one_existing(node, 1)]
}
fn choose_one_existing(node: &Node, player_index: usize) -> Command {
let ln_n = (node.score_sum.visit_count as f32).ln();
let c = 100.;
let multiplier = if player_index == 0 { 1. } else { -1. };
node.player_score_sums[player_index]
.iter()
.max_by_key(|(_command, score_sum)| {
(multiplier * (score_sum.avg().val + c * (ln_n / score_sum.visit_count as f32).sqrt()))
as i32
})
.map(|(command, _score_sum)| *command)
.unwrap_or_else(|| Command::new(Action::DoNothing))
}
fn update(node: &mut Node, commands: [Command; 2], score: Score) {
*node.player_score_sums[0]
.entry(commands[0])
.or_insert_with(ScoreSum::new) += score;
*node.player_score_sums[1]
.entry(commands[1])
.or_insert_with(ScoreSum::new) += score;
node.score_sum += score;
}
fn rollout_moves(state: &GameBoard, player_index: usize) -> ArrayVec<[Command; 8]> {
// TODO: Have this return one move, chosen randomly?
// TODO: Allow new select / bomb moves
if let Some(worm) = state.players[player_index].active_worm() {
let shoots = state.sensible_shoot_commands(player_index, worm.position, worm.weapon_range);
if !shoots.is_empty() {
return shoots;
}
state.valid_move_commands(player_index)
} else {
[Command::new(Action::DoNothing)].into_iter().cloned().collect()
}
}
fn valid_moves(state: &GameBoard, player_index: usize) -> ArrayVec<[Command; 17]> {
// TODO: Move / Dig, Shoot, Bomb, Select to another worm and repeat
// 24 move/digs
// 24 shoots
// 109 bombs (sub those out of range)
// 1 nothing
// TOTAL: 158 possible moves
if let Some(worm) = state.players[player_index].active_worm() {
state.valid_shoot_commands()
.iter()
.chain(state.valid_move_commands(player_index).iter())
.chain(state.valid_bomb_commands(player_index).iter())
.cloned()
.collect()
} else {
[Command::new(Action::DoNothing)].into_iter().cloned().collect()
}
}
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