void update_pv(SearchStack ss[], int ply);
void sp_update_pv(SearchStack *pss, SearchStack ss[], int ply);
bool connected_moves(const Position &pos, Move m1, Move m2);
+ bool value_is_mate(Value value);
bool move_is_killer(Move m, const SearchStack& ss);
Depth extension(const Position &pos, Move m, bool pvNode, bool check, bool singleReply, bool mateThreat, bool* dangerous);
bool ok_to_do_nullmove(const Position &pos);
assert(ply >= 0 && ply < PLY_MAX);
assert(threadID >= 0 && threadID < ActiveThreads);
- // Initialize, and make an early exit in case of an aborted search,
- // an instant draw, maximum ply reached, etc.
- if (AbortSearch || thread_should_stop(threadID))
- return Value(0);
-
if (depth < OnePly)
return qsearch(pos, ss, alpha, beta, Depth(0), ply, threadID);
+ // Initialize, and make an early exit in case of an aborted search,
+ // an instant draw, maximum ply reached, etc.
init_node(pos, ss, ply, threadID);
+ // After init_node() that calls poll()
+ if (AbortSearch || thread_should_stop(threadID))
+ return Value(0);
+
if (pos.is_draw())
return VALUE_DRAW;
movesSearched[moveCount++] = ss[ply].currentMove = move;
if (moveIsCapture)
- ss[ply].currentMoveCaptureValue = pos.midgame_value_of_piece_on(move_to(move));
- else if (move_is_ep(move))
- ss[ply].currentMoveCaptureValue = PawnValueMidgame;
+ ss[ply].currentMoveCaptureValue =
+ move_is_ep(move)? PawnValueMidgame : pos.midgame_value_of_piece_on(move_to(move));
else
ss[ply].currentMoveCaptureValue = Value(0);
assert(ply >= 0 && ply < PLY_MAX);
assert(threadID >= 0 && threadID < ActiveThreads);
- EvalInfo ei;
+ if (depth < OnePly)
+ return qsearch(pos, ss, beta-1, beta, Depth(0), ply, threadID);
// Initialize, and make an early exit in case of an aborted search,
// an instant draw, maximum ply reached, etc.
+ init_node(pos, ss, ply, threadID);
+
+ // After init_node() that calls poll()
if (AbortSearch || thread_should_stop(threadID))
return Value(0);
- if (depth < OnePly)
- return qsearch(pos, ss, beta-1, beta, Depth(0), ply, threadID);
-
- init_node(pos, ss, ply, threadID);
-
if (pos.is_draw())
return VALUE_DRAW;
+ EvalInfo ei;
+
if (ply >= PLY_MAX - 1)
return evaluate(pos, ei, threadID);
if ( allowNullmove
&& depth > OnePly
&& !isCheck
+ && !value_is_mate(beta)
&& ok_to_do_nullmove(pos)
&& approximateEval >= beta - NullMoveMargin)
{
UndoInfo u;
pos.do_null_move(u);
- int R = (depth > 7 ? 4 : 3);
+ int R = (depth >= 4 * OnePly ? 4 : 3); // Null move dynamic reduction
Value nullValue = -search(pos, ss, -(beta-1), depth-R*OnePly, ply+1, false, threadID);
// Check for a null capture artifact, if the value without the null capture
- // is above beta then there is a good possibility that this is a cut-node.
- // We will do an IID later to find a ttMove.
+ // is above beta then mark the node as a suspicious failed low. We will verify
+ // later if we are really under threat.
if ( UseNullDrivenIID
&& nullValue < beta
&& depth > 6 * OnePly
+ &&!value_is_mate(nullValue)
&& ttMove == MOVE_NONE
&& ss[ply + 1].currentMove != MOVE_NONE
&& pos.move_is_capture(ss[ply + 1].currentMove)
pos.undo_null_move(u);
- if (nullValue >= beta)
+ if (value_is_mate(nullValue))
+ {
+ /* Do not return unproven mates */
+ }
+ else if (nullValue >= beta)
{
if (depth < 6 * OnePly)
return beta;
}
}
// Null move search not allowed, try razoring
- else if ( (approximateEval < beta - RazorMargin && depth < RazorDepth)
- ||(approximateEval < beta - PawnValueMidgame && depth <= OnePly))
+ else if ( !value_is_mate(beta)
+ && approximateEval < beta - RazorMargin
+ && depth < RazorDepth)
{
Value v = qsearch(pos, ss, beta-1, beta, Depth(0), ply, threadID);
- if (v < beta)
+ if (v < beta - RazorMargin / 2)
return v;
}
{
// The null move failed low due to a suspicious capture. Perhaps we
// are facing a null capture artifact due to the side to move change
- // and this is a cut-node. So it's a good time to search for a ttMove.
+ // and this position should fail high. So do a normal search with a
+ // reduced depth to get a good ttMove to use in the following full
+ // depth search.
Move tm = ss[ply].threatMove;
assert(tm != MOVE_NONE);
&& !moveIsCapture
&& !move_promotion(move))
{
+ // History pruning. See ok_to_prune() definition.
if ( moveCount >= 2 + int(depth)
&& ok_to_prune(pos, move, ss[ply].threatMove, depth))
continue;
+ // Value based pruning.
if (depth < 3 * OnePly && approximateEval < beta)
{
if (futilityValue == VALUE_NONE)
assert(ply >= 0 && ply < PLY_MAX);
assert(threadID >= 0 && threadID < ActiveThreads);
- EvalInfo ei;
-
// Initialize, and make an early exit in case of an aborted search,
// an instant draw, maximum ply reached, etc.
+ init_node(pos, ss, ply, threadID);
+
+ // After init_node() that calls poll()
if (AbortSearch || thread_should_stop(threadID))
return Value(0);
- init_node(pos, ss, ply, threadID);
-
if (pos.is_draw())
return VALUE_DRAW;
return value_from_tt(tte->value(), ply);
// Evaluate the position statically
- Value staticValue = evaluate(pos, ei, threadID);
+ EvalInfo ei;
+ bool isCheck = pos.is_check();
+ Value staticValue = (isCheck ? -VALUE_INFINITE : evaluate(pos, ei, threadID));
if (ply == PLY_MAX - 1)
- return staticValue;
+ return evaluate(pos, ei, threadID);
// Initialize "stand pat score", and return it immediately if it is
// at least beta.
- Value bestValue = (pos.is_check() ? -VALUE_INFINITE : staticValue);
+ Value bestValue = staticValue;
if (bestValue >= beta)
return bestValue;
// Initialize a MovePicker object for the current position, and prepare
// to search the moves. Because the depth is <= 0 here, only captures,
// queen promotions and checks (only if depth == 0) will be generated.
- MovePicker mp = MovePicker(pos, false, MOVE_NONE, EmptySearchStack, depth, &ei);
+ bool pvNode = (beta - alpha != 1);
+ MovePicker mp = MovePicker(pos, pvNode, MOVE_NONE, EmptySearchStack, depth, isCheck ? NULL : &ei);
Move move;
int moveCount = 0;
Bitboard dcCandidates = mp.discovered_check_candidates();
- bool isCheck = pos.is_check();
- bool pvNode = (beta - alpha != 1);
bool enoughMaterial = pos.non_pawn_material(pos.side_to_move()) > RookValueMidgame;
// Loop through the moves until no moves remain or a beta cutoff
Value futilityValue = staticValue
+ Max(pos.midgame_value_of_piece_on(move_to(move)),
pos.endgame_value_of_piece_on(move_to(move)))
+ + (move_is_ep(move) ? PawnValueEndgame : Value(0))
+ FutilityMargin0
+ ei.futilityMargin;
assert(move_is_ok(move));
- ss[sp->ply].currentMoveCaptureValue = move_is_ep(move)?
- PawnValueMidgame : pos.midgame_value_of_piece_on(move_to(move));
+ if (moveIsCapture)
+ ss[sp->ply].currentMoveCaptureValue =
+ move_is_ep(move)? PawnValueMidgame : pos.midgame_value_of_piece_on(move_to(move));
+ else
+ ss[sp->ply].currentMoveCaptureValue = Value(0);
lock_grab(&(sp->lock));
int moveCount = ++sp->moves;
}
+ // value_is_mate() checks if the given value is a mate one
+ // eventually compensated for the ply.
+
+ bool value_is_mate(Value value) {
+
+ assert(abs(value) <= VALUE_INFINITE);
+
+ return value <= value_mated_in(PLY_MAX)
+ || value >= value_mate_in(PLY_MAX);
+ }
+
+
// move_is_killer() checks if the given move is among the
// killer moves of that ply.
Depth extension(const Position &pos, Move m, bool pvNode, bool check,
bool singleReply, bool mateThreat, bool* dangerous) {
+ assert(m != MOVE_NONE);
+
Depth result = Depth(0);
*dangerous = check || singleReply || mateThreat;
*dangerous = true;
}
- if ( pos.midgame_value_of_piece_on(move_to(m)) >= RookValueMidgame
+ if ( pos.move_is_capture(m)
+ && pos.type_of_piece_on(move_to(m)) != PAWN
&& ( pos.non_pawn_material(WHITE) + pos.non_pawn_material(BLACK)
- pos.midgame_value_of_piece_on(move_to(m)) == Value(0))
- && !move_promotion(m))
+ && !move_promotion(m)
+ && !move_is_ep(m))
{
result += PawnEndgameExtension[pvNode];
*dangerous = true;
// value of the threatening piece, don't prune move which defend it.
if ( !PruneDefendingMoves
&& threat != MOVE_NONE
- && pos.type_of_piece_on(tto) != NO_PIECE_TYPE
+ && pos.move_is_capture(threat)
&& ( pos.midgame_value_of_piece_on(tfrom) >= pos.midgame_value_of_piece_on(tto)
|| pos.type_of_piece_on(tfrom) == KING)
&& pos.move_attacks_square(m, tto))
projects / stockfish / blobdiff