Introduce SimpleHash class

[stockfish] / src / tt.h

diff --git a/src/tt.h b/src/tt.h
index 9babce8cdc9f10e14500c1f9c4e5cdc6a071d033..f2928fb9e84b4b754ae9c1ecfb9a1c01b7778a56 100644 (file)
--- a/src/tt.h
+++ b/src/tt.h
@@ -34,6 +34,39 @@
 //// Types
 ////
 
+
+/// A simple fixed size hash table used to store pawns and material
+/// configurations. It is basically just an array of Entry objects.
+/// Without cluster concept or overwrite policy.
+
+template<class Entry, int HashSize>
+class SimpleHash {
+
+  SimpleHash(const SimpleHash&);
+  SimpleHash& operator=(const SimpleHash&);
+
+public:
+  SimpleHash() {
+
+    entries = new Entry[HashSize];
+    if (!entries)
+    {
+        std::cerr << "Failed to allocate " << HashSize * sizeof(Entry)
+                  << " bytes for material hash table." << std::endl;
+        exit(EXIT_FAILURE);
+    }
+    memset(entries, 0, HashSize * sizeof(Entry));
+  }
+
+  ~SimpleHash() { delete [] entries; }
+
+  Entry* find(Key key) const { return entries + unsigned(key & (HashSize - 1)); }
+
+protected:
+  Entry* entries;
+};
+
+
 /// The TTEntry class is the class of transposition table entries
 ///
 /// A TTEntry needs 128 bits to be stored
@@ -59,11 +92,12 @@ public:
 
       key32 = k;
       data = (m & 0x1FFFF) | (t << 21) | (g << 23);
-      value16     = int16_t(v);
-      depth16     = int16_t(d);
-      staticValue = int16_t(statV);
-      staticValueMargin  = int16_t(kd);
+      value16     = (int16_t)v;
+      depth16     = (int16_t)d;
+      staticValue = (int16_t)statV;
+      staticValueMargin  = (int16_t)kd;
   }
+  void set_generation(int g) { data = move() | (type() << 21) | (g << 23); }
 
   uint32_t key() const { return key32; }
   Depth depth() const { return Depth(depth16); }
@@ -114,11 +148,12 @@ public:
   TTEntry* retrieve(const Key posKey) const;
   void new_search();
   TTEntry* first_entry(const Key posKey) const;
+  void refresh(const TTEntry* tte) const;
 
 private:
   size_t size;
   TTCluster* entries;
-  uint8_t generation;
+  uint8_t generation; // To properly compare, size must be smaller then TT stored value
 };
 
 extern TranspositionTable TT;
@@ -130,7 +165,16 @@ extern TranspositionTable TT;
 
 inline TTEntry* TranspositionTable::first_entry(const Key posKey) const {
 
-  return entries[uint32_t(posKey) & (size - 1)].data;
+  return entries[((uint32_t)posKey) & (size - 1)].data;
+}
+
+
+/// TranspositionTable::refresh updates the 'generation' value of the TTEntry
+/// to avoid aging. Normally called after a TT hit, before to return.
+
+inline void TranspositionTable::refresh(const TTEntry* tte) const {
+
+  const_cast<TTEntry*>(tte)->set_generation(generation);
 }
 
 #endif // !defined(TT_H_INCLUDED)