/// find_first() takes a book key as input, and does a binary search through
/// the book file for the given key. Returns the index of the leftmost book
/// entry with the same key as the input.
public int find_first(Key key)
{
int low = 0, mid, high = (int)(stream.Length / SIZE_OF_BOOKENTRY) - 1;
PolyglotBook.Entry e = new PolyglotBook.Entry();;
Debug.Assert(low <= high);
while (low < high)
{
mid = (low + high) / 2;
Debug.Assert(mid >= low && mid < high);
stream.Seek(mid * SIZE_OF_BOOKENTRY, SeekOrigin.Begin);
read(ref e);
if (key <= e.key)
{
high = mid;
}
else
{
low = mid + 1;
}
}
Debug.Assert(low == high);
return(low);
}
/// operator>>() reads sizeof(T) chars from the file's binary byte stream and
/// converts them in a number of type T. A Polyglot book stores numbers in
/// big-endian format.
public bool read(ref PolyglotBook.Entry e)
{
if (stream.Length == stream.Position)
{
return(false);
}
byte[] t = new byte[SIZE_OF_BOOKENTRY];
stream.Read(t, 0, (int)SIZE_OF_BOOKENTRY);
e.key =
(((UInt64)t[0]) << 56) |
(((UInt64)t[1]) << 48) |
(((UInt64)t[2]) << 40) |
(((UInt64)t[3]) << 32) |
(((UInt64)t[4]) << 24) |
(((UInt64)t[5]) << 16) |
(((UInt64)t[6]) << 8) |
(((UInt64)t[7]) << 0);
e.move = (UInt16)(
(((UInt64)t[8]) << 8) |
(((UInt64)t[9]) << 0));
e.count = (UInt16)(
(((UInt64)t[10]) << 8) |
(((UInt64)t[11]) << 0));
e.learn = (UInt32)(
(((UInt64)t[12]) << 24) |
(((UInt64)t[13]) << 16) |
(((UInt64)t[14]) << 8) |
(((UInt64)t[15]) << 0));
return(true);
}
/// probe() tries to find a book move for the given position. If no move is
/// found returns MOVE_NONE. If pickBest is true returns always the highest
/// rated move, otherwise randomly chooses one, based on the move score.
public Move probe(Position pos, string fName, bool pickBest)
{
if (fName == null || (fileName != fName && !open(fName)))
{
return(MoveS.MOVE_NONE);
}
PolyglotBook.Entry e = new PolyglotBook.Entry();
UInt16 best = 0;
uint sum = 0;
Move move = MoveS.MOVE_NONE;
Key key = polyglot_key(pos);
stream.Seek(find_first(key) * SIZE_OF_BOOKENTRY, SeekOrigin.Begin);
while (read(ref e) && e.key == key)
{
best = Math.Max(best, e.count);
sum += e.count;
// Choose book move according to its score. If a move has a very
// high score it has higher probability to be choosen than a move
// with lower score. Note that first entry is always chosen.
if ((sum != 0 && ((((uint)RKiss.rand64()) % sum) < e.count)) ||
(pickBest && e.count == best))
{
move = (e.move);
}
}
if (move == 0)
{
return(MoveS.MOVE_NONE);
}
// A PolyGlot book move is encoded as follows:
//
// bit 0- 5: destination square (from 0 to 63)
// bit 6-11: origin square (from 0 to 63)
// bit 12-14: promotion piece (from KNIGHT == 1 to QUEEN == 4)
//
// Castling moves follow "king captures rook" representation. So in case book
// move is a promotion we have to convert to our representation, in all the
// other cases we can directly compare with a Move after having masked out
// the special Move's flags (bit 14-15) that are not supported by PolyGlot.
int pt = (move >> 12) & 7;
if (pt != 0)
{
move = Types.make(Types.from_sq(move), Types.to_sq(move), MoveTypeS.PROMOTION, (pt + 1));
}
// Add 'special move' flags and verify it is legal
for (MoveList ml = new MoveList(pos, GenTypeS.LEGAL); ml.mlist[ml.cur].move != MoveS.MOVE_NONE; ++ml)
{
if (move == (ml.move() ^ Types.type_of_move(ml.move())))
{
return(ml.move());
}
}
return(MoveS.MOVE_NONE);
}
