bishop/src/hash.rs

use game::Game;
use evaluate::PosValue;
use std::collections::{HashMap};
use std::hash::{BuildHasher, Hasher, Hash};
use log::info;

#[derive(Clone)]
pub enum EntryType {
    Value,
    LowerBound,
    UpperBound,
}

#[derive(Clone)]
pub struct CacheEntry {
    entry_type: EntryType,
    depth: i32,
    value: PosValue
}

impl CacheEntry {
    pub fn new_value(depth: i32, value: PosValue) -> Self {
        CacheEntry {
            entry_type: EntryType::Value,
            depth,
            value
        }
    }
}

pub struct Cache {
    hashmap: HashMap<Game, CacheEntry>,
}

impl Cache {
    pub fn new() -> Self {
        Cache {
            hashmap: HashMap::new()
        }
    }

    pub fn lookup(&self, game_pos: &Game) -> Option<CacheEntry> {
        self.hashmap.get(game_pos).map(|x| x.clone())
    }
    
    pub fn cache(&mut self, game_pos: &Game, ce: CacheEntry) {
        if self.hashmap.len() > 1000000 {
            let first_key = self.hashmap.keys().next().unwrap().clone();
            self.hashmap.remove(&first_key);
        }
        self.hashmap.insert(game_pos.clone(), ce);
        if self.hashmap.len() % 1024 == 0 {
            info!("hash contains {} items", self.hashmap.len());
        }
    }
}