use crate::CheckersBitBoard;
#[cfg(debug_assertions)]
const TABLE_SIZE: usize = 1_000_000 / std::mem::size_of::<TranspositionTableEntry>();
#[cfg(not(debug_assertions))]
const TABLE_SIZE: usize = 10_000_000 / std::mem::size_of::<TranspositionTableEntry>();
const EMPTY_ENTRY: Option<TranspositionTableEntry> = None;
static mut REPLACE_TABLE: [Option<TranspositionTableEntry>; TABLE_SIZE] = [EMPTY_ENTRY; TABLE_SIZE];
static mut DEPTH_TABLE: [Option<TranspositionTableEntry>; TABLE_SIZE] = [EMPTY_ENTRY; TABLE_SIZE];
#[derive(Copy, Clone, Debug)]
struct TranspositionTableEntry {
board: CheckersBitBoard,
eval: f32,
depth: u8,
}
pub struct TranspositionTableReference {
replace_table: &'static mut [Option<TranspositionTableEntry>; TABLE_SIZE],
depth_table: &'static mut [Option<TranspositionTableEntry>; TABLE_SIZE],
}
impl TranspositionTableEntry {
const fn new(board: CheckersBitBoard, eval: f32, depth: u8) -> Self {
Self { board, eval, depth }
}
}
impl TranspositionTableReference {
pub fn new() -> Self {
Self {
replace_table: unsafe { &mut REPLACE_TABLE },
depth_table: unsafe { &mut DEPTH_TABLE },
}
}
pub fn get(self, board: CheckersBitBoard, depth: u8) -> Option<f32> {
// try the replace table
let entry = unsafe {
self.replace_table
.get_unchecked(board.hash_code() as usize % TABLE_SIZE)
};
if let Some(entry) = *entry {
if entry.board == board && entry.depth >= depth {
return Some(entry.eval);
}
}
// try the depth table
let entry = unsafe {
self.depth_table
.get_unchecked(board.hash_code() as usize % TABLE_SIZE)
};
match *entry {
Some(entry) => {
if entry.board == board {
if entry.depth >= depth {
Some(entry.eval)
} else {
None
}
} else {
None
}
}
None => None,
}
}
pub fn insert(self, board: CheckersBitBoard, eval: f32, depth: u8) {
// insert to the replace table
let entry = unsafe {
self.replace_table
.get_unchecked_mut(board.hash_code() as usize % TABLE_SIZE)
};
*entry = Some(TranspositionTableEntry::new(board, eval, depth));
// insert to the depth table, only if the new depth is higher
let entry = unsafe {
self.depth_table
.get_unchecked_mut(board.hash_code() as usize % TABLE_SIZE)
};
match *entry {
Some(entry_val) => {
if depth >= entry_val.depth {
*entry = Some(TranspositionTableEntry::new(board, eval, depth));
}
}
None => *entry = Some(TranspositionTableEntry::new(board, eval, depth)),
}
}
}
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