Position& pos = RootPosition;
Chess960 = pos.is_chess960();
Eval::RootColor = pos.side_to_move();
+ Eval::ValueDraw[ Eval::RootColor] = VALUE_DRAW - Eval::ContemptFactor;
+ Eval::ValueDraw[~Eval::RootColor] = VALUE_DRAW + Eval::ContemptFactor;
TimeMgr.init(Limits, pos.startpos_ply_counter(), pos.side_to_move());
TT.new_search();
H.clear();
Depth ext, newDepth;
Value bestValue, value, ttValue;
Value refinedValue, nullValue, futilityValue;
- bool pvMove, inCheck, singularExtensionNode, givesCheck;
+ bool inCheck, givesCheck, pvMove, singularExtensionNode;
bool captureOrPromotion, dangerous, doFullDepthSearch;
int moveCount, playedMoveCount;
{
// Step 2. Check for aborted search and immediate draw
if (Signals.stop || pos.is_draw<false>() || ss->ply > MAX_PLY)
- return Eval::ValueDrawContempt;
+ return Eval::ValueDraw[pos.side_to_move()];
// Step 3. Mate distance pruning. Even if we mate at the next move our score
// would be at best mate_in(ss->ply+1), but if alpha is already bigger because
if (PvNode && value < beta)
{
alpha = value; // Update alpha here! Always alpha < beta
- if (SpNode) sp->alpha = alpha;
+ if (SpNode) sp->alpha = value;
}
else // Fail high
{
assert(NT == PV || NT == NonPV);
assert(alpha >= -VALUE_INFINITE && alpha < beta && beta <= VALUE_INFINITE);
- assert((alpha == beta - 1) || PvNode);
+ assert(PvNode || (alpha == beta - 1));
assert(depth <= DEPTH_ZERO);
StateInfo st;
- Move ttMove, move, bestMove;
- Value ttValue, bestValue, value, evalMargin, futilityValue, futilityBase;
- bool inCheck, enoughMaterial, givesCheck, evasionPrunable;
const TTEntry* tte;
+ Key posKey;
+ Move ttMove, move, bestMove;
+ Value bestValue, value, ttValue, futilityValue, futilityBase;
+ bool inCheck, givesCheck, enoughMaterial, evasionPrunable;
Depth ttDepth;
- Bound bt;
- Value oldAlpha = alpha;
+ inCheck = pos.in_check();
ss->currentMove = bestMove = MOVE_NONE;
ss->ply = (ss-1)->ply + 1;
// Check for an instant draw or maximum ply reached
if (pos.is_draw<true>() || ss->ply > MAX_PLY)
- return Eval::ValueDrawContempt;
+ return Eval::ValueDraw[pos.side_to_move()];
+
+ // Transposition table lookup. At PV nodes, we don't use the TT for
+ // pruning, but only for move ordering.
+ posKey = pos.key();
+ tte = TT.probe(posKey);
+ ttMove = tte ? tte->move() : MOVE_NONE;
+ ttValue = tte ? value_from_tt(tte->value(),ss->ply) : VALUE_NONE;
// Decide whether or not to include checks, this fixes also the type of
// TT entry depth that we are going to use. Note that in qsearch we use
// only two types of depth in TT: DEPTH_QS_CHECKS or DEPTH_QS_NO_CHECKS.
- inCheck = pos.in_check();
- ttDepth = (inCheck || depth >= DEPTH_QS_CHECKS ? DEPTH_QS_CHECKS : DEPTH_QS_NO_CHECKS);
-
- // Transposition table lookup. At PV nodes, we don't use the TT for
- // pruning, but only for move ordering.
- tte = TT.probe(pos.key());
- ttMove = (tte ? tte->move() : MOVE_NONE);
- ttValue = tte ? value_from_tt(tte->value(),ss->ply) : VALUE_ZERO;
+ ttDepth = inCheck || depth >= DEPTH_QS_CHECKS ? DEPTH_QS_CHECKS : DEPTH_QS_NO_CHECKS;
if (!PvNode && tte && can_return_tt(tte, ttDepth, ttValue, beta))
{
// Evaluate the position statically
if (inCheck)
{
+ ss->eval = ss->evalMargin = VALUE_NONE;
bestValue = futilityBase = -VALUE_INFINITE;
- ss->eval = evalMargin = VALUE_NONE;
enoughMaterial = false;
}
else
{
assert(tte->static_value() != VALUE_NONE);
- evalMargin = tte->static_value_margin();
ss->eval = bestValue = tte->static_value();
+ ss->evalMargin = tte->static_value_margin();
}
else
- ss->eval = bestValue = evaluate(pos, evalMargin);
+ ss->eval = bestValue = evaluate(pos, ss->evalMargin);
// Stand pat. Return immediately if static value is at least beta
if (bestValue >= beta)
{
if (!tte)
- TT.store(pos.key(), value_to_tt(bestValue, ss->ply), BOUND_LOWER, DEPTH_NONE, MOVE_NONE, ss->eval, evalMargin);
+ TT.store(pos.key(), value_to_tt(bestValue, ss->ply), BOUND_LOWER, DEPTH_NONE, MOVE_NONE, ss->eval, ss->evalMargin);
return bestValue;
}
if (PvNode && bestValue > alpha)
alpha = bestValue;
- futilityBase = ss->eval + evalMargin + Value(128);
+ futilityBase = ss->eval + ss->evalMargin + Value(128);
enoughMaterial = pos.non_pawn_material(pos.side_to_move()) > RookValueMg;
}
CheckInfo ci(pos);
// Loop through the moves until no moves remain or a beta cutoff occurs
- while ( bestValue < beta
- && (move = mp.next_move<false>()) != MOVE_NONE)
+ while ((move = mp.next_move<false>()) != MOVE_NONE)
{
assert(is_ok(move));
// Make and search the move
pos.do_move(move, st, ci, givesCheck);
- value = -qsearch<NT>(pos, ss+1, -beta, -alpha, depth-ONE_PLY);
+ value = -qsearch<NT>(pos, ss+1, -beta, -alpha, depth - ONE_PLY);
pos.undo_move(move);
assert(value > -VALUE_INFINITE && value < VALUE_INFINITE);
- // New best move?
+ // Check for new best move
if (value > bestValue)
{
bestValue = value;
- bestMove = move;
- if ( PvNode
- && value > alpha
- && value < beta) // We want always alpha < beta
- alpha = value;
+ if (value > alpha)
+ {
+ if (PvNode && value < beta) // Update alpha here! Always alpha < beta
+ {
+ alpha = value;
+ bestMove = move;
+ }
+ else // Fail high
+ {
+ TT.store(posKey, value_to_tt(value, ss->ply), BOUND_LOWER,
+ ttDepth, move, ss->eval, ss->evalMargin);
+
+ return value;
+ }
+ }
}
}
if (inCheck && bestValue == -VALUE_INFINITE)
return mated_in(ss->ply); // Plies to mate from the root
- // Update transposition table
- move = bestValue <= oldAlpha ? MOVE_NONE : bestMove;
- bt = bestValue <= oldAlpha ? BOUND_UPPER
- : bestValue >= beta ? BOUND_LOWER : BOUND_EXACT;
-
- TT.store(pos.key(), value_to_tt(bestValue, ss->ply), bt, ttDepth, move, ss->eval, evalMargin);
+ TT.store(posKey, value_to_tt(bestValue, ss->ply),
+ PvNode && bestMove != MOVE_NONE ? BOUND_EXACT : BOUND_UPPER,
+ ttDepth, bestMove, ss->eval, ss->evalMargin);
assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE);