// Step 7. Razoring (skipped when in check)
if ( !PvNode
- && depth < 3 * ONE_PLY
+ && depth <= ONE_PLY
&& eval + RazorMargin <= alpha)
- {
- if (depth <= ONE_PLY)
- return qsearch<NonPV, false>(pos, ss, alpha, alpha+1);
-
- Value ralpha = alpha - RazorMargin;
- Value v = qsearch<NonPV, false>(pos, ss, ralpha, ralpha+1);
- if (v <= ralpha)
- return v;
- }
+ return qsearch<NonPV, false>(pos, ss, alpha, alpha+1);
// Step 8. Futility pruning: child node (skipped when in check)
if ( !rootNode
assert(depth >= 5 * ONE_PLY);
pos.do_move(move, st);
- value = -search<NonPV>(pos, ss+1, -rbeta, -rbeta+1, depth - 4 * ONE_PLY, !cutNode, false);
+
+ // Perform a preliminary search at depth 1 to verify that the move holds.
+ // We will only do this search if the depth is not 5, thus avoiding two
+ // searches at depth 1 in a row.
+ if (depth != 5 * ONE_PLY)
+ value = -search<NonPV>(pos, ss+1, -rbeta, -rbeta+1, ONE_PLY, !cutNode, true);
+
+ // If the first search was skipped or was performed and held, perform
+ // the regular search.
+ if (depth == 5 * ONE_PLY || value >= rbeta)
+ value = -search<NonPV>(pos, ss+1, -rbeta, -rbeta+1, depth - 4 * ONE_PLY, !cutNode, false);
+
pos.undo_move(move);
if (value >= rbeta)
return value;
search<NT>(pos, ss, alpha, beta, d, cutNode, true);
tte = TT.probe(posKey, ttHit);
+ ttValue = ttHit ? value_from_tt(tte->value(), ss->ply) : VALUE_NONE;
ttMove = ttHit ? tte->move() : MOVE_NONE;
}
// Transposition table lookup
posKey = pos.key();
tte = TT.probe(posKey, ttHit);
- ttMove = ttHit ? tte->move() : MOVE_NONE;
ttValue = ttHit ? value_from_tt(tte->value(), ss->ply) : VALUE_NONE;
+ ttMove = ttHit ? tte->move() : MOVE_NONE;
if ( !PvNode
&& ttHit