stellar

UCI Chess engine written in C++20

git clone git://git.dimitrijedobrota.com/stellar.git

commit	7bb17c1e229bb64c927a65833273bd21fe07e2bd
parent	67d1edbf1daf0345b19c76305a4f6bd88bb70493
author	Dimitrije Dobrota <mail@dimitrijedobrota.com>
date	Sat, 5 Aug 2023 13:04:04 +0200

Principle Variation Search

Diffstat:

M	CMakeLists.txt	\|	+-
M	src/engine/engine.c	\|	+++++++++++---

2 files changed, 12 insertions(+), 4 deletions(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt

@@ -3,7 +3,7 @@ set(CMAKE_EXPORT_COMPILE_COMMANDS ON)

project(

Stellar

VERSION 0.0.10

VERSION 0.0.11

DESCRIPTION "Chess engine written in C"

HOMEPAGE_URL https://git.dimitrijedobrota.com/stellar.git

LANGUAGES C

diff --git a/src/engine/engine.c b/src/engine/engine.c

@@ -153,6 +153,7 @@ int negamax(Stats stats, const Board board, int alpha, int beta, int depth) {

move_list_sort(stats, &list);

int legal_moves = 0;

int found_pv = 0;

for (int i = 0; i < move_list_size(&list); i++) {

Move move = move_list_move(&list, i);

@@ -162,7 +163,15 @@ int negamax(Stats stats, const Board board, int alpha, int beta, int depth) {

}

stats->ply++;

int score = -negamax(stats, &copy, -beta, -alpha, depth - 1);

int score = alpha;

if (found_pv)

score = -negamax(stats, &copy, -alpha - 1, -alpha, depth - 1);

// no PVS or the last one failed

if (!found_pv || (score > alpha) && (score < beta))

score = -negamax(stats, &copy, -beta, -alpha, depth - 1);

stats->ply--;

legal_moves++;

@@ -179,7 +188,7 @@ int negamax(Stats stats, const Board board, int alpha, int beta, int depth) {

stats->history_moves[piece_index(move_piece(move))]

[move_target(move)] += depth;

alpha = score;

found_pv = 1;

stats->pv_table[ply][ply] = move;

for (int i = stats->ply + 1; i < stats->pv_length[ply + 1]; i++)

stats->pv_table[ply][i] = stats->pv_table[ply + 1][i];

@@ -208,7 +217,6 @@ void search_position(const Board *board, int depth) {

for (int crnt = 1; crnt <= depth; crnt++) {

stats.follow_pv = 1;

stats.nodes = 0;

int score = negamax(&stats, board, -50000, 50000, crnt);