Use a flag in TT to track null search values

Add VALUE_TYPE_NS_LO to enum ValueType and use it when
saving in TT a value from a null search.

Currently no action is performed, the next patch will enable
the new type.

No functional change.

Signed-off-by: Marco Costalba <mcostalba@gmail.com>

diff --git a/src/search.cpp b/src/search.cpp
index fd5687ea9714ab625bbc8a6cf106003ab293bb34..cd874ff816156bfcfd036c65de3443a917325341 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -1388,7 +1388,7 @@ namespace {
             {
                 assert(value_to_tt(nullValue, ply) == nullValue);
 
-                TT.store(posKey, nullValue, VALUE_TYPE_LOWER, depth, MOVE_NONE);
+                TT.store(posKey, nullValue, VALUE_TYPE_NS_LO, depth, MOVE_NONE);
                 return nullValue;
             }
         } else {

diff --git a/src/tt.h b/src/tt.h
index 272e752b3157c6237fd62fb5fc3cc992cef86740..021019be4c18ef71f2a04fe18c71ebfd51fa8bc9 100644 (file)
--- a/src/tt.h
+++ b/src/tt.h
@@ -46,8 +46,8 @@
 /// the 32 bits of the data field are so defined
 ///
 /// bit  0-16: move
-/// bit 17-19: not used
-/// bit 20-22: value type
+/// bit 17-18: not used
+/// bit 19-22: value type
 /// bit 23-31: generation
 
 class TTEntry {
@@ -55,14 +55,14 @@ class TTEntry {
 public:
   TTEntry() {}
   TTEntry(uint32_t k, Value v, ValueType t, Depth d, Move m, int generation)
-        : key_ (k), data((m & 0x1FFFF) | (t << 20) | (generation << 23)),
+        : key_ (k), data((m & 0x1FFFF) | (t << 19) | (generation << 23)),
           value_(int16_t(v)), depth_(int16_t(d)) {}
 
   uint32_t key() const { return key_; }
   Depth depth() const { return Depth(depth_); }
   Move move() const { return Move(data & 0x1FFFF); }
   Value value() const { return Value(value_); }
-  ValueType type() const { return ValueType((data >> 20) & 7); }
+  ValueType type() const { return ValueType((data >> 19) & 0xF); }
   int generation() const { return (data >> 23); }
 
 private:

diff --git a/src/value.h b/src/value.h
index 62d9458eb9bc0508560e30208ccb15d9cf6ec00c..4b62027267847592c63ef4a50895dc5b292625e4 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,
 };