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);
-
+ bool ok_to_history(const Position &pos, Move m);
+ void update_history(const Position& pos, Move m, Depth depth,
+ Move movesSearched[], int moveCount);
bool fail_high_ply_1();
int current_search_time();
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
+ // history counters, and killer moves.
if (AbortSearch || thread_should_stop(threadID))
return bestValue;
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))
+ if (ok_to_history(pos, m)) // Only non capture moves are considered
{
- 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);
-
- if (m != ss[ply].killer1)
- {
- ss[ply].killer2 = ss[ply].killer1;
- ss[ply].killer1 = m;
- }
+ update_history(pos, m, depth, movesSearched, moveCount);
+ 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);
}
// Mate distance pruning
if (value_mated_in(ply) >= beta)
return beta;
+
if (value_mate_in(ply + 1) < beta)
return beta - 1;
// Loop through all legal moves until no moves remain or a beta cutoff
// occurs.
- while( bestValue < beta
- && (move = mp.get_next_move()) != MOVE_NONE
- && !thread_should_stop(threadID))
+ while ( bestValue < beta
+ && (move = mp.get_next_move()) != MOVE_NONE
+ && !thread_should_stop(threadID))
{
assert(move_is_ok(move));
if (depth < 3 * OnePly && approximateEval < beta)
{
if (futilityValue == VALUE_NONE)
- futilityValue = evaluate(pos, ei, threadID) + (depth < 2 * OnePly ? FutilityMargin1 : FutilityMargin2);
+ futilityValue = evaluate(pos, ei, threadID)
+ + (depth < 2 * OnePly ? FutilityMargin1 : FutilityMargin2);
if (futilityValue < beta)
{
- if(futilityValue > bestValue)
+ if (futilityValue > bestValue)
bestValue = futilityValue;
continue;
}
bestValue = value;
if (value >= beta)
update_pv(ss, ply);
+
if (value == value_mate_in(ply + 1))
ss[ply].mateKiller = move;
}
// Split?
- if( ActiveThreads > 1
- && bestValue < beta
- && depth >= MinimumSplitDepth
- && Iteration <= 99
- && idle_thread_exists(threadID)
- && !AbortSearch
- && !thread_should_stop(threadID)
- && split(pos, ss, ply, &beta, &beta, &bestValue, depth, &moveCount,
- &mp, dcCandidates, threadID, false))
+ if ( ActiveThreads > 1
+ && bestValue < beta
+ && depth >= MinimumSplitDepth
+ && Iteration <= 99
+ && idle_thread_exists(threadID)
+ && !AbortSearch
+ && !thread_should_stop(threadID)
+ && split(pos, ss, ply, &beta, &beta, &bestValue, depth, &moveCount,
+ &mp, dcCandidates, threadID, false))
break;
}
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
+ // history counters, and killer moves.
if (AbortSearch || thread_should_stop(threadID))
return bestValue;
else
{
Move m = ss[ply].pv[ply];
- if (pos.square_is_empty(move_to(m)) && !move_promotion(m) && !move_is_ep(m))
+ if (ok_to_history(pos, m)) // Only non capture moves are considered
{
- 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);
-
+ update_history(pos, m, depth, movesSearched, moveCount);
if (m != ss[ply].killer1)
{
ss[ply].killer2 = ss[ply].killer1;
Value qsearch(Position &pos, SearchStack ss[], Value alpha, Value beta,
Depth depth, int ply, int threadID) {
- Value staticValue, bestValue, value;
- EvalInfo ei;
assert(alpha >= -VALUE_INFINITE && alpha <= VALUE_INFINITE);
assert(beta >= -VALUE_INFINITE && beta <= VALUE_INFINITE);
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.
- if(AbortSearch || thread_should_stop(threadID))
- return Value(0);
+ if (AbortSearch || thread_should_stop(threadID))
+ return Value(0);
init_node(pos, ss, ply, threadID);
- if(pos.is_draw())
- return VALUE_DRAW;
+ if (pos.is_draw())
+ return VALUE_DRAW;
// Evaluate the position statically:
- staticValue = evaluate(pos, ei, threadID);
+ Value staticValue = evaluate(pos, ei, threadID);
- if(ply == PLY_MAX - 1) return staticValue;
+ if (ply == PLY_MAX - 1)
+ return staticValue;
// Initialize "stand pat score", and return it immediately if it is
// at least beta.
- if(pos.is_check())
- bestValue = -VALUE_INFINITE;
- else {
- bestValue = staticValue;
- if(bestValue >= beta)
+ Value bestValue = (pos.is_check() ? -VALUE_INFINITE : staticValue);
+
+ if (bestValue >= beta)
return bestValue;
- if(bestValue > alpha)
+
+ if (bestValue > alpha)
alpha = bestValue;
- }
// Initialize a MovePicker object for the current position, and prepare
// to search the moves. Because the depth is <= 0 here, only captures,
// Loop through the moves until no moves remain or a beta cutoff
// occurs.
- while(alpha < beta && ((move = mp.get_next_move()) != MOVE_NONE)) {
- UndoInfo u;
+ while ( alpha < beta
+ && (move = mp.get_next_move()) != MOVE_NONE)
+ {
+ assert(move_is_ok(move));
+
bool moveIsCheck = pos.move_is_check(move, dcCandidates);
bool moveIsPassedPawnPush = pos.move_is_passed_pawn_push(move);
- assert(move_is_ok(move));
-
moveCount++;
ss[ply].currentMove = move;
// Futility pruning
- if(UseQSearchFutilityPruning && !isCheck && !moveIsCheck &&
- !move_promotion(move) && !moveIsPassedPawnPush &&
- beta - alpha == 1 &&
- pos.non_pawn_material(pos.side_to_move()) > RookValueMidgame) {
- Value futilityValue =
- staticValue
- + Max(pos.midgame_value_of_piece_on(move_to(move)),
- pos.endgame_value_of_piece_on(move_to(move)))
- + FutilityMargin0
- + ei.futilityMargin;
- if(futilityValue < alpha) {
- if(futilityValue > bestValue)
- bestValue = futilityValue;
- continue;
- }
+ if ( UseQSearchFutilityPruning
+ && !isCheck
+ && !moveIsCheck
+ && !move_promotion(move)
+ && !moveIsPassedPawnPush
+ && beta - alpha == 1
+ && pos.non_pawn_material(pos.side_to_move()) > RookValueMidgame)
+ {
+ Value futilityValue = staticValue
+ + Max(pos.midgame_value_of_piece_on(move_to(move)),
+ pos.endgame_value_of_piece_on(move_to(move)))
+ + FutilityMargin0
+ + ei.futilityMargin;
+
+ if (futilityValue < alpha)
+ {
+ if (futilityValue > bestValue)
+ bestValue = futilityValue;
+ continue;
+ }
}
// Don't search captures and checks with negative SEE values.
- if(!isCheck && !move_promotion(move) &&
- pos.midgame_value_of_piece_on(move_from(move)) >
- pos.midgame_value_of_piece_on(move_to(move)) &&
- pos.see(move) < 0)
- continue;
+ if ( !isCheck
+ && !move_promotion(move)
+ && (pos.midgame_value_of_piece_on(move_from(move)) >
+ pos.midgame_value_of_piece_on(move_to(move)))
+ && pos.see(move) < 0)
+ continue;
// Make and search the move.
+ UndoInfo u;
pos.do_move(move, u, dcCandidates);
- value = -qsearch(pos, ss, -beta, -alpha, depth-OnePly, ply+1, threadID);
+ Value value = -qsearch(pos, ss, -beta, -alpha, depth-OnePly, ply+1, threadID);
pos.undo_move(move, u);
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 > bestValue)
+ {
+ bestValue = value;
+ if (value > alpha)
+ {
+ alpha = value;
+ update_pv(ss, ply);
+ }
+ }
}
// All legal moves have been searched. A special case: If we're in check
// and no legal moves were found, it is checkmate:
- if(pos.is_check() && moveCount == 0) // Mate!
- return value_mated_in(ply);
+ if (pos.is_check() && moveCount == 0) // Mate!
+ return value_mated_in(ply);
assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE);
}
- // ok_to_use_TT() returns true if a transposition table score
- // can be used at a given point in search.
-
- bool ok_to_use_TT(const TTEntry* tte, Depth depth, Value beta, int ply) {
-
- Value v = value_from_tt(tte->value(), ply);
-
- return ( tte->depth() >= depth
- || v >= Max(value_mate_in(100), beta)
- || v < Min(value_mated_in(100), beta))
-
- && ( (is_lower_bound(tte->type()) && v >= beta)
- || (is_upper_bound(tte->type()) && v < beta));
- }
-
-
/// The RootMove class
// Constructor
}
+ // ok_to_use_TT() returns true if a transposition table score
+ // can be used at a given point in search.
+
+ bool ok_to_use_TT(const TTEntry* tte, Depth depth, Value beta, int ply) {
+
+ Value v = value_from_tt(tte->value(), ply);
+
+ return ( tte->depth() >= depth
+ || v >= Max(value_mate_in(100), beta)
+ || v < Min(value_mated_in(100), beta))
+
+ && ( (is_lower_bound(tte->type()) && v >= beta)
+ || (is_upper_bound(tte->type()) && v < beta));
+ }
+
+
+ // ok_to_history() returns true if a move m can be stored
+ // in history. Should be a non capturing move.
+
+ bool ok_to_history(const Position& pos, Move m) {
+
+ return pos.square_is_empty(move_to(m))
+ && !move_promotion(m)
+ && !move_is_ep(m);
+ }
+
+
+ // update_history() registers a good move that produced a beta-cutoff
+ // in history and marks as failures all the other moves of that ply.
+
+ void update_history(const Position& pos, Move m, Depth depth,
+ Move movesSearched[], int moveCount) {
+
+ H.success(pos.piece_on(move_from(m)), m, depth);
+
+ for (int i = 0; i < moveCount - 1; i++)
+ if (ok_to_history(pos, movesSearched[i]) && m != movesSearched[i])
+ H.failure(pos.piece_on(move_from(movesSearched[i])), movesSearched[i]);
+ }
+
// fail_high_ply_1() checks if some thread is currently resolving a fail
// high at ply 1 at the node below the first root node. This information
// is used for time managment.