case PH_GOOD_CAPTURES:
numOfMoves = generate_captures(pos, moves);
score_captures();
+ capSquares = EmptyBoardBB;
movesPicked = 0;
break;
// where it is possible to recapture with the hanging piece). Exchanging
// big pieces before capturing a hanging piece probably helps to reduce
// the subtree size.
+ // While scoring captures it moves all captures with negative SEE values
+ // to the badCaptures[] array.
Move m;
int seeValue;
else
moves[i].score = int(pos.midgame_value_of_piece_on(move_to(m)))
-int(pos.type_of_piece_on(move_from(m)));
- } else
+ }
+ else
+ {
+ // Losing capture, move it to the badCaptures[] array
+ assert(numOfBadCaptures < 63);
moves[i].score = seeValue;
+ badCaptures[numOfBadCaptures++] = moves[i];
+ moves[i--] = moves[--numOfMoves];
+ }
}
}
}
-/// find_best_index() loops across the moves and returns index of
-/// the highest scored one.
+/// find_best_index() loops across the moves and returns index of\r
+/// the highest scored one. There is also a second version that\r
+/// lowers the priority of moves that attack the same square,\r
+/// so that if the best move that attack a square fails the next\r
+/// move picked attacks a different square if any, not the same one.
int MovePicker::find_best_index() {
return bestIndex;
}
+int MovePicker::find_best_index(Bitboard* squares, int values[]) {\r
+\r
+ int hs;\r
+ Move m;\r
+ Square to;\r
+ int bestScore = -10000000, bestIndex = -1;\r
+\r
+ for (int i = movesPicked; i < numOfMoves; i++)\r
+ {\r
+ m = moves[i].move;\r
+ to = move_to(m);\r
+ \r
+ if (!bit_is_set(*squares, to))\r
+ {\r
+ // Init at first use\r
+ set_bit(squares, to);\r
+ values[to] = 0;\r
+ }\r
+\r
+ hs = moves[i].score - values[to];\r
+ if (hs > bestScore)\r
+ {\r
+ bestIndex = i;\r
+ bestScore = hs;\r
+ }\r
+ }\r
+\r
+ if (bestIndex != -1)\r
+ {\r
+ // Raise value of the picked square, so next attack\r
+ // to the same square will get low priority.\r
+ to = move_to(moves[bestIndex].move);\r
+ values[to] += 0xB00;\r
+ }\r
+ return bestIndex;\r
+}
+
/// MovePicker::pick_move_from_list() picks the move with the biggest score
/// from a list of generated moves (moves[] or badCaptures[], depending on
/// the current move generation phase). It takes care not to return the
/// transposition table move if that has already been serched previously.
-/// While picking captures in the PH_GOOD_CAPTURES phase (i.e. while picking
-/// non-losing captures in the main search), it moves all captures with
-/// negative SEE values to the badCaptures[] array.
Move MovePicker::pick_move_from_list() {
while (movesPicked < numOfMoves)
{
- int bestScore = -10000000;
- bestIndex = -1;
- for (int i = movesPicked; i < numOfMoves; i++)
- {
- if (moves[i].score < 0)
- {
- // Losing capture, move it to the badCaptures[] array
- assert(numOfBadCaptures < 63);
- badCaptures[numOfBadCaptures++] = moves[i];
- moves[i--] = moves[--numOfMoves];
- }
- else if (moves[i].score > bestScore)
- {
- bestIndex = i;
- bestScore = moves[i].score;
- }
- }
+ bestIndex = find_best_index(&capSquares, capSqValues);
+
if (bestIndex != -1) // Found a good capture
{
move = moves[bestIndex].move;