Move Book::get_move(const Position &pos) const {
if(this->is_open()) {
int bestMove = 0, bestScore = 0, move, score;
uint64_t key = book_key(pos);
BookEntry entry;
for(int i = this->find_key(key); i < bookSize; i++) {
this->read_entry(entry, i);
if(entry.key != key)
break;
move = entry.move;
score = entry.count;
assert(score > 0);
bestScore += score;
if(int(genrand_int32() % bestScore) < score)
bestMove = move;
}
if(bestMove != 0) {
MoveStack moves[256];
int n, j;
n = generate_legal_moves(pos, moves);
for(j = 0; j < n; j++)
if((int(moves[j].move) & 07777) == bestMove)
return moves[j].move;
}
}
return MOVE_NONE;
}
std::tuple<Move, Value>
AperyBook::probe(const Position &pos, const std::string &fname, bool pick_best)
{
AperyBookEntry entry;
uint16_t best = 0;
uint32_t sum = 0;
Move move = kMoveNone;
Key key = book_key(pos);
Value min_book_score = static_cast<Value>(static_cast<int>(Options["Min_Book_Score"]));
Value score = kValueZero;
if (file_name_ != fname && !open(fname.c_str()))
return std::make_tuple(kMoveNone, kValueZero);
binary_search(key);
while (read(reinterpret_cast<char*>(&entry), sizeof(entry)), entry.key == key && good())
{
best = std::max(best, entry.count);
sum += entry.count;
if
(
min_book_score <= entry.score
&&
(
(random_() % sum < entry.count)
||
(pick_best && entry.count == best)
)
)
{
Square to = to_square(entry.from_to_pro & 0x007fU);
int from_raw = (entry.from_to_pro >> 7) & 0x007fU;
if (from_raw >= kBoardSquare)
{
move = move_init(to, to_drop_piece_type(static_cast<Square>(from_raw)));
}
else
{
Square from = to_square(from_raw);
PieceType pt_from = type_of(pos.square(from));
if (entry.from_to_pro & kPromoted)
move = move_init(from, to, pt_from, type_of(pos.square(to)), true);
else
move = move_init(from, to, pt_from, type_of(pos.square(to)), false);
}
score = entry.score;
}
}
