bishop/src/hash.rs

use game::Game;
use evaluate::PosValue;
use std::collections::{HashMap};
use log::info;
use zobrist;

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

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

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

    pub fn new_upper(depth: i32, beta: PosValue) -> Self {
        CacheEntry {
            entry_type: EntryType::UpperBound,
            depth,
            value: beta,
        }
    }

    pub fn new_lower(depth: i32, alpha: PosValue) -> Self {
        CacheEntry {
            entry_type: EntryType::LowerBound,
            depth,
            value: alpha,
        }
    }
}

pub struct Cache {
    hashmap: HashMap<zobrist::Hash, CacheEntry>,
    max_capacity: usize
}

#[derive(Clone)]
pub struct RepetitionTable {
    hashmap: HashMap<zobrist::Hash, i32>,
}

impl Cache {
    pub fn new() -> Self {
        Cache {
            hashmap: HashMap::new(),
            max_capacity: 40000000
        }
    }

    pub fn lookup(&self, game_pos: &Game) -> Option<CacheEntry> {
        self.hashmap.get(&game_pos.zobrist.as_ref().unwrap().1).map(|x| x.clone())
    }
    
    pub fn cache(&mut self, game_pos: &Game, ce: CacheEntry) {
        if let Some(c) = self.lookup(game_pos) {
            if c.depth > ce.depth {
                return;
            }
        }
        if self.hashmap.len() > self.max_capacity {
            //let first_key = self.hashmap.keys().next().unwrap().clone();
            //self.hashmap.remove(&first_key);
            self.hashmap.clear();
        }
        let key = game_pos.zobrist.as_ref().unwrap().1;
        self.hashmap.insert(key, ce);
        if self.hashmap.len() % (1024 * 32) == 0 {
            info!("hash contains {} items", self.hashmap.len());
        }
    }
}


impl RepetitionTable {
    pub fn new() -> Self {
        RepetitionTable {
            hashmap: HashMap::with_capacity(256)
        }
    }

    pub fn clear(&mut self) {
        self.hashmap.clear();
    }

    pub fn increment(&mut self, hash: zobrist::Hash) -> i32 {
        if let Some(entry) = self.hashmap.get_mut(&hash) {
            *entry += 1;
            *entry
        }
        else {
            self.hashmap.insert(hash, 1);
            1
        }
    }

    pub fn decrement(&mut self, hash: zobrist::Hash) {
        if let Some(entry) = self.hashmap.get_mut(&hash) {
            *entry -= 1;
            if *entry == 0 {
                self.hashmap.remove(&hash);
            }
        }
    }
}