Maximum aspiration delta of 64

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index eb19b51d9c994c5d11e8c9c7abfb195806e475af..5196e86277880817d623b6c94645874d0ebe744e 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -657,7 +657,7 @@ namespace {
             int prevDelta1 = bestValues[iteration - 1] - bestValues[iteration - 2];
             int prevDelta2 = bestValues[iteration - 2] - bestValues[iteration - 3];
 
-            aspirationDelta = Max(abs(prevDelta1) + abs(prevDelta2) / 2, 16);
+            aspirationDelta = Min(Max(abs(prevDelta1) + abs(prevDelta2) / 2, 16), 64);
             aspirationDelta = (aspirationDelta + 7) / 8 * 8; // Round to match grainSize
 
             alpha = Max(bestValues[iteration - 1] - aspirationDelta, -VALUE_INFINITE);
@@ -838,14 +838,13 @@ namespace {
     tte = TT.retrieve(posKey);
     ttMove = tte ? tte->move() : MOVE_NONE;
 
-    // At PV nodes, we don't use the TT for pruning, but only for move ordering.
-    // This is to avoid problems in the following areas:
-    //
-    // * Repetition draw detection
-    // * Fifty move rule detection
-    // * Searching for a mate
-    // * Printing of full PV line
-    if (!PvNode && tte && ok_to_use_TT(tte, depth, beta, ply))
+    // At PV nodes we check for exact scores, while at non-PV nodes we check for
+    // and return a fail high/low. Biggest advantage at probing at PV nodes is
+    // to have a smooth experience in analysis mode.
+    if (   !Root
+        && tte
+        && (PvNode ? tte->depth() >= depth && tte->type() == VALUE_TYPE_EXACT
+                   : ok_to_use_TT(tte, depth, beta, ply)))
     {
         TT.refresh(tte);
         ss->bestMove = ttMove; // Can be MOVE_NONE