// search when the static evaluation is at most IIDMargin below beta.
const Value IIDMargin = Value(0x100);
- // Search depth at iteration 1
- const Depth InitialDepth = OnePly;
+ // Step 11. Decide the new search depth
- // Easy move margin. An easy move candidate must be at least this much
- // better than the second best move.
- const Value EasyMoveMargin = Value(0x200);
+ // Extensions. Configurable UCI options.
+ // Array index 0 is used at non-PV nodes, index 1 at PV nodes.
+ Depth CheckExtension[2], SingleEvasionExtension[2], PawnPushTo7thExtension[2];
+ Depth PassedPawnExtension[2], PawnEndgameExtension[2], MateThreatExtension[2];
+
+ const Depth SingularExtensionDepthAtPVNodes = 6 * OnePly;
+ const Depth SingularExtensionDepthAtNonPVNodes = 8 * OnePly;
- // If the TT move is at least SingleReplyMargin better then the
+ // If the TT move is at least SingularExtensionMargin better then the
// remaining ones we will extend it.
- const Value SingleReplyMargin = Value(0x20);
+ const Value SingularExtensionMargin = Value(0x20);
+
+ // Step 12. Futility pruning
+
+ const Value FutilityMarginQS = Value(0x80);
+
+ // Futility lookup tables (initialized at startup) and their getter functions
+ int32_t FutilityMarginsMatrix[14][64]; // [depth][moveNumber]
+ int FutilityMoveCountArray[32]; // [depth]
+
+ inline Value futility_margin(Depth d, int mn) { return Value(d < 7*OnePly ? FutilityMarginsMatrix[Max(d, 0)][Min(mn, 63)] : 2 * VALUE_INFINITE); }
+ inline int futility_move_count(Depth d) { return d < 16*OnePly ? FutilityMoveCountArray[d] : 512; }
- /// Lookup tables initialized at startup
+ // Step 14. Reduced search
- // Reduction lookup tables and their getter functions
+ // Reduction lookup tables (initialized at startup) and their getter functions
int8_t PVReductionMatrix[64][64]; // [depth][moveNumber]
int8_t NonPVReductionMatrix[64][64]; // [depth][moveNumber]
inline Depth pv_reduction(Depth d, int mn) { return (Depth) PVReductionMatrix[Min(d / 2, 63)][Min(mn, 63)]; }
inline Depth nonpv_reduction(Depth d, int mn) { return (Depth) NonPVReductionMatrix[Min(d / 2, 63)][Min(mn, 63)]; }
- // Futility lookup tables and their getter functions
- const Value FutilityMarginQS = Value(0x80);
- int32_t FutilityMarginsMatrix[14][64]; // [depth][moveNumber]
- int FutilityMoveCountArray[32]; // [depth]
- inline Value futility_margin(Depth d, int mn) { return Value(d < 7*OnePly ? FutilityMarginsMatrix[Max(d, 0)][Min(mn, 63)] : 2 * VALUE_INFINITE); }
- inline int futility_move_count(Depth d) { return d < 16*OnePly ? FutilityMoveCountArray[d] : 512; }
+
+ // Search depth at iteration 1
+ const Depth InitialDepth = OnePly;
+
+ // Easy move margin. An easy move candidate must be at least this much
+ // better than the second best move.
+ const Value EasyMoveMargin = Value(0x200);
/// Variables initialized by UCI options
const Value LSNValue = value_from_centipawns(200);
bool loseOnTime = false;
- // Extensions. Array index 0 is used at non-PV nodes, index 1 at PV nodes.
- Depth CheckExtension[2], SingleEvasionExtension[2], PawnPushTo7thExtension[2];
- Depth PassedPawnExtension[2], PawnEndgameExtension[2], MateThreatExtension[2];
-
// Iteration counters
int Iteration;
// Singular extension search. We extend the TT move if its value is much better than
// its siblings. To verify this we do a reduced search on all the other moves but the
// ttMove, if result is lower then ttValue minus a margin then we extend ttMove.
- if ( depth >= 6 * OnePly
+ if ( depth >= SingularExtensionDepthAtPVNodes
&& tte
&& move == tte->move()
&& ext < OnePly
if (abs(ttValue) < VALUE_KNOWN_WIN)
{
- Value excValue = search(pos, ss, ttValue - SingleReplyMargin, depth / 2, ply, false, threadID, move);
+ Value excValue = search(pos, ss, ttValue - SingularExtensionMargin, depth / 2, ply, false, threadID, move);
- if (excValue < ttValue - SingleReplyMargin)
+ if (excValue < ttValue - SingularExtensionMargin)
ext = OnePly;
}
}
// Singular extension search. We extend the TT move if its value is much better than
// its siblings. To verify this we do a reduced search on all the other moves but the
// ttMove, if result is lower then ttValue minus a margin then we extend ttMove.
- if ( depth >= 8 * OnePly
+ if ( depth >= SingularExtensionDepthAtNonPVNodes
&& tte
&& move == tte->move()
&& !excludedMove // Do not allow recursive single-reply search
if (abs(ttValue) < VALUE_KNOWN_WIN)
{
- Value excValue = search(pos, ss, ttValue - SingleReplyMargin, depth / 2, ply, false, threadID, move);
+ Value excValue = search(pos, ss, ttValue - SingularExtensionMargin, depth / 2, ply, false, threadID, move);
- if (excValue < ttValue - SingleReplyMargin)
+ if (excValue < ttValue - SingularExtensionMargin)
ext = OnePly;
}
}
continue;
// Value based pruning
- Depth predictedDepth = newDepth - nonpv_reduction(depth, moveCount); //FIXME: We are ignoring condition: depth >= 3*OnePly, BUG??
+ Depth predictedDepth = newDepth - nonpv_reduction(depth, moveCount); // We illogically ignore reduction condition depth >= 3*OnePly
futilityValueScaled = ss[ply].eval + futility_margin(predictedDepth, moveCount)
+ H.gain(pos.piece_on(move_from(move)), move_to(move)) + 45;