+ // Maximum depth for use of dynamic threat detection when null move fails low
+ const Depth ThreatDepth = 5 * OnePly;
+
+ // Step 9. Internal iterative deepening
+
+ // Minimum depth for use of internal iterative deepening
+ const Depth IIDDepthAtPVNodes = 5 * OnePly;
+ const Depth IIDDepthAtNonPVNodes = 8 * OnePly;
+
+ // At Non-PV nodes we do an internal iterative deepening search
+ // when the static evaluation is at most IIDMargin below beta.
+ const Value IIDMargin = Value(0x100);
+
+ // Step 11. Decide the new search depth
+
+ // 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];
+
+ // Minimum depth for use of singular extension
+ const Depth SingularExtensionDepthAtPVNodes = 6 * OnePly;
+ const Depth SingularExtensionDepthAtNonPVNodes = 8 * OnePly;
+
+ // If the TT move is at least SingularExtensionMargin better then the