const bool UseIIDAtPVNodes = true;
const bool UseIIDAtNonPVNodes = false;
+ // Use null move driven internal iterative deepening?
+ bool UseNullDrivenIID = true;
+
// Internal iterative deepening margin. At Non-PV moves, when
// UseIIDAtNonPVNodes is true, we do an internal iterative deepening search
// when the static evaluation is at most IIDMargin below beta.
// Time managment variables
int SearchStartTime;
int MaxNodes, MaxDepth;
- int MaxSearchTime, AbsoluteMaxSearchTime, ExtraSearchTime, TimeAdvantage;
+ int MaxSearchTime, AbsoluteMaxSearchTime, ExtraSearchTime;
Move BestRootMove, PonderMove, EasyMove;
int RootMoveNumber;
bool InfiniteSearch;
void sp_update_pv(SearchStack *pss, SearchStack ss[], int ply);
bool connected_moves(const Position &pos, Move m1, Move m2);
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* extendable);
+ 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);
bool ok_to_prune(const Position &pos, Move m, Move threat, Depth d);
bool ok_to_use_TT(const TTEntry* tte, Depth depth, Value beta, int ply);
int myIncrement = increment[side_to_move];
int oppTime = time[1 - side_to_move];
- TimeAdvantage = myTime - oppTime;
-
if (!movesToGo) // Sudden death time control
{
if (myIncrement)
MaxSearchTime = myTime / 30 + myIncrement;
AbsoluteMaxSearchTime = Max(myTime / 4, myIncrement - 100);
} else { // Blitz game without increment
- MaxSearchTime = myTime / 40;
+ MaxSearchTime = myTime / 30;
AbsoluteMaxSearchTime = myTime / 8;
}
}
ExtraSearchTime = BestMoveChangesByIteration[Iteration] * (MaxSearchTime / 2)
+ BestMoveChangesByIteration[Iteration-1] * (MaxSearchTime / 3);
- // If we need some more and we are in time advantage take it
- if (ExtraSearchTime > 0 && TimeAdvantage > 2 * MaxSearchTime)
- ExtraSearchTime += MaxSearchTime / 2;
-
// Try to guess if the current iteration is the last one or the last two
LastIterations = (current_search_time() > ((MaxSearchTime + ExtraSearchTime)*58) / 128);
<< " currmovenumber " << i + 1 << std::endl;
// Decide search depth for this move
- bool dummy;
- ext = extension(pos, move, true, pos.move_is_check(move), false, false, &dummy);
+ bool dangerous;
+ ext = extension(pos, move, true, pos.move_is_check(move), false, false, &dangerous);
newDepth = (Iteration - 2) * OnePly + ext + InitialDepth;
// Make the move, and search it
Value value, bestValue = -VALUE_INFINITE;
Bitboard dcCandidates = mp.discovered_check_candidates();
bool isCheck = pos.is_check();
- bool mateThreat = MateThreatExtension[1] > Depth(0)
- && pos.has_mate_threat(opposite_color(pos.side_to_move()));
+ bool mateThreat = pos.has_mate_threat(opposite_color(pos.side_to_move()));
// Loop through all legal moves until no moves remain or a beta cutoff
// occurs.
bool singleReply = (isCheck && mp.number_of_moves() == 1);
bool moveIsCheck = pos.move_is_check(move, dcCandidates);
bool moveIsCapture = pos.move_is_capture(move);
- bool moveIsPassedPawnPush = pos.move_is_passed_pawn_push(move);
movesSearched[moveCount++] = ss[ply].currentMove = move;
ss[ply].currentMoveCaptureValue = Value(0);
// Decide the new search depth
- bool extendable;
- Depth ext = extension(pos, move, true, moveIsCheck, singleReply, mateThreat, &extendable);
+ bool dangerous;
+ Depth ext = extension(pos, move, true, moveIsCheck, singleReply, mateThreat, &dangerous);
Depth newDepth = depth - OnePly + ext;
// Make and search the move
// Try to reduce non-pv search depth by one ply if move seems not problematic,
// if the move fails high will be re-searched at full depth.
if ( depth >= 2*OnePly
- && !extendable
&& moveCount >= LMRPVMoves
+ && !dangerous
&& !moveIsCapture
&& !move_promotion(move)
- && !moveIsPassedPawnPush
&& !move_is_castle(move)
&& !move_is_killer(move, ss[ply]))
{
if (tte && ok_to_use_TT(tte, depth, beta, ply))
{
- ss[ply].currentMove = ttMove; // can be MOVE_NONE ?
+ ss[ply].currentMove = ttMove; // can be MOVE_NONE
return value_from_tt(tte->value(), ply);
}
Value approximateEval = quick_evaluate(pos);
bool mateThreat = false;
+ bool nullDrivenIID = false;
bool isCheck = pos.is_check();
// Null move search
UndoInfo u;
pos.do_null_move(u);
int R = (depth > 7 ? 4 : 3);
+
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.
+ if ( UseNullDrivenIID
+ && nullValue < beta
+ && depth > 6 * OnePly
+ && ttMove == MOVE_NONE
+ && ss[ply + 1].currentMove != MOVE_NONE
+ && pos.move_is_capture(ss[ply + 1].currentMove)
+ && pos.see(ss[ply + 1].currentMove) * PawnValueMidgame + nullValue > beta - IIDMargin)
+ nullDrivenIID = true;
+
pos.undo_null_move(u);
if (nullValue >= beta)
// low score (which will cause the reduced move to fail high in the
// parent node, which will trigger a re-search with full depth).
if (nullValue == value_mated_in(ply + 2))
+ {
mateThreat = true;
-
+ nullDrivenIID = false;
+ }
ss[ply].threatMove = ss[ply + 1].currentMove;
if ( depth < ThreatDepth
&& ss[ply - 1].reduction
search(pos, ss, beta, Min(depth/2, depth-2*OnePly), ply, false, threadID);
ttMove = ss[ply].pv[ply];
}
+ else if (nullDrivenIID)
+ {
+ // 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.
+ Move tm = ss[ply].threatMove;
+
+ assert(tm != MOVE_NONE);
+
+ search(pos, ss, beta, Min(depth/2, depth-3*OnePly), ply, false, threadID);
+ ttMove = ss[ply].pv[ply];
+ ss[ply].threatMove = tm;
+ }
// Initialize a MovePicker object for the current position, and prepare
// to search all moves:
bool singleReply = (isCheck && mp.number_of_moves() == 1);
bool moveIsCheck = pos.move_is_check(move, dcCandidates);
bool moveIsCapture = pos.move_is_capture(move);
- bool moveIsPassedPawnPush = pos.move_is_passed_pawn_push(move);
movesSearched[moveCount++] = ss[ply].currentMove = move;
// Decide the new search depth
- bool extendable;
- Depth ext = extension(pos, move, false, moveIsCheck, singleReply, mateThreat, &extendable);
+ bool dangerous;
+ Depth ext = extension(pos, move, false, moveIsCheck, singleReply, mateThreat, &dangerous);
Depth newDepth = depth - OnePly + ext;
// Futility pruning
if ( useFutilityPruning
- && !extendable
+ && !dangerous
&& !moveIsCapture
- && !moveIsPassedPawnPush
&& !move_promotion(move))
{
if ( moveCount >= 2 + int(depth)
// Try to reduce non-pv search depth by one ply if move seems not problematic,
// if the move fails high will be re-searched at full depth.
- if ( depth >= 2*OnePly
- && !extendable
- && moveCount >= LMRNonPVMoves
+ if ( depth >= 2*OnePly
+ && moveCount >= LMRNonPVMoves
+ && !dangerous
&& !moveIsCapture
&& !move_promotion(move)
- && !moveIsPassedPawnPush
&& !move_is_castle(move)
&& !move_is_killer(move, ss[ply]))
{
{
assert(move_is_ok(move));
- bool moveIsCheck = pos.move_is_check(move, dcCandidates);
- bool moveIsPassedPawnPush = pos.move_is_passed_pawn_push(move);
-
moveCount++;
ss[ply].currentMove = move;
// Futility pruning
if ( UseQSearchFutilityPruning
+ && enoughMaterial
&& !isCheck
- && !moveIsCheck
- && !move_promotion(move)
- && !moveIsPassedPawnPush
&& !pvNode
- && enoughMaterial)
+ && !move_promotion(move)
+ && !pos.move_is_check(move, dcCandidates)
+ && !pos.move_is_passed_pawn_push(move))
{
Value futilityValue = staticValue
+ Max(pos.midgame_value_of_piece_on(move_to(move)),
bool moveIsCheck = pos.move_is_check(move, sp->dcCandidates);
bool moveIsCapture = pos.move_is_capture(move);
- bool moveIsPassedPawnPush = pos.move_is_passed_pawn_push(move);
lock_grab(&(sp->lock));
int moveCount = ++sp->moves;
ss[sp->ply].currentMove = move;
// Decide the new search depth.
- bool extendable;
- Depth ext = extension(pos, move, false, moveIsCheck, false, false, &extendable);
+ bool dangerous;
+ Depth ext = extension(pos, move, false, moveIsCheck, false, false, &dangerous);
Depth newDepth = sp->depth - OnePly + ext;
// Prune?
if ( useFutilityPruning
- && !extendable
+ && !dangerous
&& !moveIsCapture
- && !moveIsPassedPawnPush
&& !move_promotion(move)
&& moveCount >= 2 + int(sp->depth)
&& ok_to_prune(pos, move, ss[sp->ply].threatMove, sp->depth))
// Try to reduce non-pv search depth by one ply if move seems not problematic,
// if the move fails high will be re-searched at full depth.
- if ( !extendable
+ if ( !dangerous
&& moveCount >= LMRNonPVMoves
&& !moveIsCapture
- && !moveIsPassedPawnPush
&& !move_promotion(move)
&& !move_is_castle(move)
&& !move_is_killer(move, ss[sp->ply]))
{
bool moveIsCheck = pos.move_is_check(move, sp->dcCandidates);
bool moveIsCapture = pos.move_is_capture(move);
- bool moveIsPassedPawnPush = pos.move_is_passed_pawn_push(move);
assert(move_is_ok(move));
ss[sp->ply].currentMove = move;
// Decide the new search depth.
- bool extendable;
- Depth ext = extension(pos, move, true, moveIsCheck, false, false, &extendable);
+ bool dangerous;
+ Depth ext = extension(pos, move, true, moveIsCheck, false, false, &dangerous);
Depth newDepth = sp->depth - OnePly + ext;
// Make and search the move.
// Try to reduce non-pv search depth by one ply if move seems not problematic,
// if the move fails high will be re-searched at full depth.
- if ( !extendable
+ if ( !dangerous
&& moveCount >= LMRPVMoves
&& !moveIsCapture
- && !moveIsPassedPawnPush
&& !move_promotion(move)
&& !move_is_castle(move)
&& !move_is_killer(move, ss[sp->ply]))
// extension() decides whether a move should be searched with normal depth,
// or with extended depth. Certain classes of moves (checking moves, in
- // particular) are searched with bigger depth than ordinary moves.
+ // particular) are searched with bigger depth than ordinary moves and in
+ // any case are marked as 'dangerous'. Note that also if a move is not
+ // extended, as example because the corresponding UCI option is set to zero,
+ // the move is marked as 'dangerous' so, at least, we avoid to prune it.
- Depth extension(const Position &pos, Move m, bool pvNode,
- bool check, bool singleReply, bool mateThreat, bool* extendable) {
+ Depth extension(const Position &pos, Move m, bool pvNode, bool check,
+ bool singleReply, bool mateThreat, bool* dangerous) {
Depth result = Depth(0);
- *extendable = check || singleReply || mateThreat;
+ *dangerous = check || singleReply || mateThreat;
if (check)
result += CheckExtension[pvNode];
if (pos.move_is_pawn_push_to_7th(m))
{
result += PawnPushTo7thExtension[pvNode];
- *extendable = true;
+ *dangerous = true;
}
if (pos.move_is_passed_pawn_push(m))
{
result += PassedPawnExtension[pvNode];
- *extendable = true;
+ *dangerous = true;
}
if ( pos.midgame_value_of_piece_on(move_to(m)) >= RookValueMidgame
&& !move_promotion(m))
{
result += PawnEndgameExtension[pvNode];
- *extendable = true;
+ *dangerous = true;
}
if ( pvNode
&& pos.see(m) >= 0)
{
result += OnePly/2;
- *extendable = true;
+ *dangerous = true;
}
return Min(result, OnePly);
projects / stockfish / blobdiff