Don't overwrite exsisting TT with null search value

[stockfish] / src / value.h

diff --git a/src/value.h b/src/value.h
index 62d9458eb9bc0508560e30208ccb15d9cf6ec00c..dd2c39412267b94efa9d065fd5ade03b830dc5d2 100644 (file)
--- a/src/value.h
+++ b/src/value.h
@@ -33,13 +33,16 @@
 ////
 
 enum ValueType {
-  VALUE_TYPE_NONE = 0,
+  VALUE_TYPE_NONE =  0,
   VALUE_TYPE_UPPER = 1,  // Upper bound
   VALUE_TYPE_LOWER = 2,  // Lower bound
   VALUE_TYPE_EXACT = 3,  // Exact score
-  VALUE_TYPE_EVAL  = 4,  // Evaluation cache
-  VALUE_TYPE_EV_UP = 5,  // Evaluation cache for upper bound
-  VALUE_TYPE_EV_LO = 6   // Evaluation cache for lower bound
+  VALUE_TYPE_EVAL  = 4,  // Static evaluation value
+  VALUE_TYPE_NULL  = 8,  // Null search value
+
+  VALUE_TYPE_EV_UP = VALUE_TYPE_EVAL | VALUE_TYPE_UPPER,
+  VALUE_TYPE_EV_LO = VALUE_TYPE_EVAL | VALUE_TYPE_LOWER,
+  VALUE_TYPE_NS_LO = VALUE_TYPE_NULL | VALUE_TYPE_LOWER
 };