Simplify IID

STC:
LLR: 2.96 (-2.94,2.94) [-3.00,1.00]
Total: 30468 W: 5687 L: 5582 D: 19199
http://tests.stockfishchess.org/tests/view/57b1ddd80ebc591c761f63e2

LTC:
LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 87406 W: 11756 L: 11725 D: 63925
http://tests.stockfishchess.org/tests/view/57b212590ebc591c761f63f9

bench: 6554900

diff --git a/src/search.cpp b/src/search.cpp
index 9eeafbdaf22173053c0f7dd3d0f7b64207053b15..3dfd5d6de96e49289f7071602c7a05ff747c490e 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -801,13 +801,12 @@ namespace {
     }
 
     // Step 10. Internal iterative deepening (skipped when in check)
     }
 
     // Step 10. Internal iterative deepening (skipped when in check)

-    if (    depth >= (PvNode ? 5 * ONE_PLY : 8 * ONE_PLY)
+    if (    depth >= 6 * ONE_PLY

         && !ttMove
         && (PvNode || ss->staticEval + 256 >= beta))
     {
         && !ttMove
         && (PvNode || ss->staticEval + 256 >= beta))
     {

-        Depth d = depth - 2 * ONE_PLY - (PvNode ? DEPTH_ZERO : depth / 4);

         ss->skipEarlyPruning = true;
         ss->skipEarlyPruning = true;

-        search<NT>(pos, ss, alpha, beta, d, cutNode);
+        search<NT>(pos, ss, alpha, beta, 3 * depth / 4 - 2 * ONE_PLY, cutNode);

         ss->skipEarlyPruning = false;
 
         tte = TT.probe(posKey, ttHit);
         ss->skipEarlyPruning = false;
 
         tte = TT.probe(posKey, ttHit);