// We're ready to start thinking. Call the iterative deepening loop
// function:
- id_loop(pos, searchMoves);;
+ id_loop(pos, searchMoves);
if(UseLogFile)
LogFile.close();
Value search_pv(Position &pos, SearchStack ss[], Value alpha, Value beta,
Depth depth, int ply, int threadID) {
+
assert(alpha >= -VALUE_INFINITE && alpha <= VALUE_INFINITE);
assert(beta > alpha && beta <= VALUE_INFINITE);
assert(ply >= 0 && ply < PLY_MAX);
// an instant draw, maximum ply reached, etc.
Value oldAlpha = alpha;
- if(AbortSearch || thread_should_stop(threadID))
- return Value(0);
+ if (AbortSearch || thread_should_stop(threadID))
+ return Value(0);
- if(depth < OnePly)
- return qsearch(pos, ss, alpha, beta, Depth(0), ply, threadID);
+ if (depth < OnePly)
+ return qsearch(pos, ss, alpha, beta, Depth(0), ply, threadID);
init_node(pos, ss, ply, threadID);
- if(pos.is_draw())
- return VALUE_DRAW;
+ if (pos.is_draw())
+ return VALUE_DRAW;
- if(ply >= PLY_MAX - 1)
- return evaluate(pos, ei, threadID);
+ if (ply >= PLY_MAX - 1)
+ return evaluate(pos, ei, threadID);
// Mate distance pruning
alpha = Max(value_mated_in(ply), alpha);
beta = Min(value_mate_in(ply+1), beta);
- if(alpha >= beta)
- return alpha;
+ if (alpha >= beta)
+ return alpha;
// Transposition table lookup. At PV nodes, we don't use the TT for
// pruning, but only for move ordering.
Move ttMove = (tte ? tte->move() : MOVE_NONE);
// Go with internal iterative deepening if we don't have a TT move.
- if(UseIIDAtPVNodes && ttMove == MOVE_NONE && depth >= 5*OnePly) {
- search_pv(pos, ss, alpha, beta, depth-2*OnePly, ply, threadID);
- ttMove = ss[ply].pv[ply];
+ if (UseIIDAtPVNodes && ttMove == MOVE_NONE && depth >= 5*OnePly)
+ {
+ search_pv(pos, ss, alpha, beta, depth-2*OnePly, ply, threadID);
+ ttMove = ss[ply].pv[ply];
}
// Initialize a MovePicker object for the current position, and prepare
// to search all moves:
MovePicker mp = MovePicker(pos, true, ttMove, ss[ply].mateKiller,
ss[ply].killer1, ss[ply].killer2, depth);
+
Move move, movesSearched[256];
int moveCount = 0;
Value value, bestValue = -VALUE_INFINITE;
Bitboard dcCandidates = mp.discovered_check_candidates();
- bool mateThreat =
- MateThreatExtension[1] > Depth(0)
- && pos.has_mate_threat(opposite_color(pos.side_to_move()));
+ bool mateThreat = MateThreatExtension[1] > Depth(0)
+ && pos.has_mate_threat(opposite_color(pos.side_to_move()));
// Loop through all legal moves until no moves remain or a beta cutoff
// occurs.
- while(alpha < beta && !thread_should_stop(threadID)
- && (move = mp.get_next_move()) != MOVE_NONE) {
- UndoInfo u;
- Depth ext, newDepth;
+ while ( alpha < beta
+ && (move = mp.get_next_move()) != MOVE_NONE
+ && !thread_should_stop(threadID))
+ {
+ assert(move_is_ok(move));
+
bool singleReply = (pos.is_check() && 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);
- assert(move_is_ok(move));
movesSearched[moveCount++] = ss[ply].currentMove = move;
- ss[ply].currentMoveCaptureValue = move_is_ep(move)?
+ ss[ply].currentMoveCaptureValue = move_is_ep(move) ?
PawnValueMidgame : pos.midgame_value_of_piece_on(move_to(move));
// Decide the new search depth.
- ext = extension(pos, move, true, moveIsCheck, singleReply, mateThreat);
- newDepth = depth - OnePly + ext;
+ Depth ext = extension(pos, move, true, moveIsCheck, singleReply, mateThreat);
+ Depth newDepth = depth - OnePly + ext;
// Make and search the move.
+ UndoInfo u;
pos.do_move(move, u, dcCandidates);
- if(moveCount == 1)
- value = -search_pv(pos, ss, -beta, -alpha, newDepth, ply+1, threadID);
- else {
- if(depth >= 2*OnePly && ext == Depth(0) && moveCount >= LMRPVMoves
- && !moveIsCapture && !move_promotion(move)
- && !moveIsPassedPawnPush && !move_is_castle(move)
- && move != ss[ply].killer1 && move != ss[ply].killer2) {
- ss[ply].reduction = OnePly;
- value = -search(pos, ss, -alpha, newDepth-OnePly, ply+1, true,
- threadID);
+ if (moveCount == 1) // The first move in list is the PV
+ value = -search_pv(pos, ss, -beta, -alpha, newDepth, ply+1, threadID);
+ else
+ {
+ // 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
+ && ext == Depth(0)
+ && moveCount >= LMRPVMoves
+ && !moveIsCapture
+ && !move_promotion(move)
+ && !moveIsPassedPawnPush
+ && !move_is_castle(move)
+ && move != ss[ply].killer1
+ && move != ss[ply].killer2)
+ {
+ ss[ply].reduction = OnePly;
+ value = -search(pos, ss, -alpha, newDepth-OnePly, ply+1, true, threadID);
}
- else value = alpha + 1;
- if(value > alpha) {
- ss[ply].reduction = Depth(0);
- value = -search(pos, ss, -alpha, newDepth, ply+1, true, threadID);
- if(value > alpha && value < beta) {
- if(ply == 1 && RootMoveNumber == 1)
- // When the search fails high at ply 1 while searching the first
- // move at the root, set the flag failHighPly1. This is used for
- // time managment: We don't want to stop the search early in
- // such cases, because resolving the fail high at ply 1 could
- // result in a big drop in score at the root.
- Threads[threadID].failHighPly1 = true;
- value = -search_pv(pos, ss, -beta, -alpha, newDepth, ply+1,
- threadID);
- Threads[threadID].failHighPly1 = false;
+ else
+ value = alpha + 1; // Just to trigger next condition
+
+ if (value > alpha) // Go with full depth non-pv search
+ {
+ ss[ply].reduction = Depth(0);
+ value = -search(pos, ss, -alpha, newDepth, ply+1, true, threadID);
+ if (value > alpha && value < beta)
+ {
+ // When the search fails high at ply 1 while searching the first
+ // move at the root, set the flag failHighPly1. This is used for
+ // time managment: We don't want to stop the search early in
+ // such cases, because resolving the fail high at ply 1 could
+ // result in a big drop in score at the root.
+ if (ply == 1 && RootMoveNumber == 1)
+ Threads[threadID].failHighPly1 = true;
+
+ // A fail high occurred. Re-search at full window (pv search)
+ value = -search_pv(pos, ss, -beta, -alpha, newDepth, ply+1, threadID);
+ Threads[threadID].failHighPly1 = false;
}
}
}
assert(value > -VALUE_INFINITE && value < VALUE_INFINITE);
// New best move?
- if(value > bestValue) {
- bestValue = value;
- if(value > alpha) {
- alpha = value;
- update_pv(ss, ply);
- if(value == value_mate_in(ply + 1))
- ss[ply].mateKiller = move;
- }
- // If we are at ply 1, and we are searching the first root move at
- // ply 0, set the 'Problem' variable if the score has dropped a lot
- // (from the computer's point of view) since the previous iteration:
- if(Iteration >= 2 &&
- -value <= ValueByIteration[Iteration-1] - ProblemMargin)
- Problem = true;
+ if (value > bestValue)
+ {
+ bestValue = value;
+ if (value > alpha)
+ {
+ alpha = value;
+ update_pv(ss, ply);
+ if (value == value_mate_in(ply + 1))
+ ss[ply].mateKiller = move;
+ }
+ // If we are at ply 1, and we are searching the first root move at
+ // ply 0, set the 'Problem' variable if the score has dropped a lot
+ // (from the computer's point of view) since the previous iteration:
+ if (Iteration >= 2 && -value <= ValueByIteration[Iteration-1] - ProblemMargin)
+ Problem = true;
}
// Split?
- if(ActiveThreads > 1 && bestValue < beta && depth >= MinimumSplitDepth
- && Iteration <= 99 && idle_thread_exists(threadID)
- && !AbortSearch && !thread_should_stop(threadID)
- && split(pos, ss, ply, &alpha, &beta, &bestValue, depth,
- &moveCount, &mp, dcCandidates, threadID, true))
- break;
+ if ( ActiveThreads > 1
+ && bestValue < beta && depth >= MinimumSplitDepth
+ && Iteration <= 99 && idle_thread_exists(threadID)
+ && !AbortSearch && !thread_should_stop(threadID)
+ && split(pos, ss, ply, &alpha, &beta, &bestValue, depth,
+ &moveCount, &mp, dcCandidates, threadID, true))
+ break;
}
// All legal moves have been searched. A special case: If there were
// no legal moves, it must be mate or stalemate:
- if(moveCount == 0) {
- if(pos.is_check())
- return value_mated_in(ply);
- else
- return VALUE_DRAW;
- }
+ if (moveCount == 0)
+ return (pos.is_check() ? value_mated_in(ply) : VALUE_DRAW);
// If the search is not aborted, update the transposition table,
// history counters, and killer moves. This code is somewhat messy,
// and definitely needs to be cleaned up. FIXME
- if(!AbortSearch && !thread_should_stop(threadID)) {
- if(bestValue <= oldAlpha)
- TT.store(pos, value_to_tt(bestValue, ply), depth, MOVE_NONE,
- VALUE_TYPE_UPPER);
- else if(bestValue >= beta) {
+ if (AbortSearch || thread_should_stop(threadID))
+ return bestValue;
+
+ if (bestValue <= oldAlpha)
+ TT.store(pos, value_to_tt(bestValue, ply), depth, MOVE_NONE, VALUE_TYPE_UPPER);
+
+ else if (bestValue >= beta)
+ {
Move m = ss[ply].pv[ply];
- if(pos.square_is_empty(move_to(m)) && !move_promotion(m) &&
- !move_is_ep(m)) {
- for(int i = 0; i < moveCount - 1; i++)
- if(pos.square_is_empty(move_to(movesSearched[i]))
- && !move_promotion(movesSearched[i])
- && !move_is_ep(movesSearched[i]))
- H.failure(pos.piece_on(move_from(movesSearched[i])),
- movesSearched[i]);
+ if (pos.square_is_empty(move_to(m)) && !move_promotion(m) && !move_is_ep(m))
+ {
+ for(int i = 0; i < moveCount - 1; i++)
+ if( pos.square_is_empty(move_to(movesSearched[i]))
+ && !move_promotion(movesSearched[i])
+ && !move_is_ep(movesSearched[i]))
+ H.failure(pos.piece_on(move_from(movesSearched[i])), movesSearched[i]);
- H.success(pos.piece_on(move_from(m)), m, depth);
+ H.success(pos.piece_on(move_from(m)), m, depth);
- if(m != ss[ply].killer1) {
+ if (m != ss[ply].killer1)
+ {
ss[ply].killer2 = ss[ply].killer1;
ss[ply].killer1 = m;
}
}
TT.store(pos, value_to_tt(bestValue, ply), depth, m, VALUE_TYPE_LOWER);
- }
- else
- TT.store(pos, value_to_tt(bestValue, ply), depth, ss[ply].pv[ply],
- VALUE_TYPE_EXACT);
}
+ else
+ TT.store(pos, value_to_tt(bestValue, ply), depth, ss[ply].pv[ply], VALUE_TYPE_EXACT);
return bestValue;
}
projects / stockfish / blobdiff