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/*
This file is part of ctak.
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
General Public License for more details.
You should have received a copy of the GNU General Public License
along with ctak. If not, see <https://www.gnu.org/licenses/>.
*/
#ifndef TT_H
#define TT_H
#include <stdint.h>
#include <actions.h>
// ===================================================================
// Types
// ===================================================================
enum TT_FLAG { TT_EXACT, TT_LOWERBOUND, TT_UPPERBOUND };
#ifdef RECORD_PV
#include <pv.h>
#endif
typedef struct tt_node_s {
uint16_t gen;
uint64_t key;
enum TT_FLAG flag;
uint8_t depth;
float value;
action_t action;
#ifdef RECORD_PV
// use for generating training data only
pv_leaf_t leaf;
#endif
} tt_entry_t;
// ===================================================================
// Variables
// ===================================================================
// Direct-mapped hash table (no chaining); one slot per key.
#define TT_SIZE ((uint32_t)((1 << 19) - 1))
// ===================================================================
// Methods
// ===================================================================
// Bump the generation counter, invalidating all entries. Called from
// negamax_init when the board size (and hence the zobrist table) changes;
// entries are otherwise kept across plies on purpose (see negamax.c).
int tt_init(void);
tt_entry_t *tt_seek(const uint64_t key);
// Store a search result for `key', returning the entry it was written to, or
// NULL when the replacement policy keeps the current occupant instead.
//
// Replacement policy per slot:
//
// - generation and key match: always update
//
// - otherwise (empty slot, stale generation, or a different key): replace the
// occupant unless it is a deeper search of a different position, which is
// kept.
tt_entry_t *tt_store(const uint64_t key, const enum TT_FLAG flag,
const uint8_t depth, const float value,
const action_t action);
#endif
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