From: Marco Costalba <mcostalba@gmail.com>
Date: Wed, 1 May 2013 20:55:23 +0000 (+0200)
Subject: Re-add "Cache line aligned TT"
X-Git-Url: https://git.sesse.net/?p=stockfish;a=commitdiff_plain;h=481eda4ca0121cfa16f5a29f364ca30ee2852409;hp=e381951a248ba4c6873dd81527926c6bdcac2aa6

Re-add "Cache line aligned TT"

But this time do not play with pointers, in
particular do not assume that size_t is an
unsigned type of the same width as pointers.

This code should be fully portable.

No functional change.
---

diff --git a/src/misc.cpp b/src/misc.cpp
index c0c00b00..477fb392 100644
--- a/src/misc.cpp
+++ b/src/misc.cpp
@@ -237,10 +237,8 @@ void prefetch(char* addr) {
 
 #  if defined(__INTEL_COMPILER) || defined(_MSC_VER)
   _mm_prefetch(addr, _MM_HINT_T0);
-  _mm_prefetch(addr+64, _MM_HINT_T0); // 64 bytes ahead
 #  else
   __builtin_prefetch(addr);
-  __builtin_prefetch(addr+64);
 #  endif
 }
 
diff --git a/src/tt.cpp b/src/tt.cpp
index 80ea493b..271b98b7 100644
--- a/src/tt.cpp
+++ b/src/tt.cpp
@@ -40,16 +40,18 @@ void TranspositionTable::set_size(size_t mbSize) {
       return;
 
   hashMask = size - ClusterSize;
-  delete [] table;
-  table = new (std::nothrow) TTEntry[size];
+  free(mem);
+  mem = malloc(size * sizeof(TTEntry) + CACHE_LINE_SIZE - 1);
 
-  if (!table)
+  if (!mem)
   {
       std::cerr << "Failed to allocate " << mbSize
                 << "MB for transposition table." << std::endl;
       exit(EXIT_FAILURE);
   }
 
+  // Align table start address to a cache line
+  for (char* c = (char*)mem; unsigned(table = (TTEntry*)(c)) % CACHE_LINE_SIZE; c++) {}
   clear(); // Operator new is not guaranteed to initialize memory to zero
 }
 
diff --git a/src/tt.h b/src/tt.h
index c7c39e90..1caa277e 100644
--- a/src/tt.h
+++ b/src/tt.h
@@ -85,7 +85,7 @@ class TranspositionTable {
   static const unsigned ClusterSize = 4; // A cluster is 64 Bytes
 
 public:
- ~TranspositionTable() { delete [] table; }
+ ~TranspositionTable() { free(mem); }
   void new_search() { generation++; }
 
   TTEntry* probe(const Key key) const;
@@ -98,6 +98,7 @@ public:
 private:
   uint32_t hashMask;
   TTEntry* table;
+  void* mem;
   uint8_t generation; // Size must be not bigger then TTEntry::generation8
 };
 
diff --git a/src/types.h b/src/types.h
index 1def7d00..dae86db3 100644
--- a/src/types.h
+++ b/src/types.h
@@ -56,10 +56,11 @@
 #   include <xmmintrin.h> // Intel and Microsoft header for _mm_prefetch()
 #  endif
 
+#define CACHE_LINE_SIZE 64
 #if defined(_MSC_VER) || defined(__INTEL_COMPILER)
-#  define CACHE_LINE_ALIGNMENT __declspec(align(64))
+#  define CACHE_LINE_ALIGNMENT __declspec(align(CACHE_LINE_SIZE))
 #else
-#  define CACHE_LINE_ALIGNMENT  __attribute__ ((aligned(64)))
+#  define CACHE_LINE_ALIGNMENT  __attribute__ ((aligned(CACHE_LINE_SIZE)))
 #endif
 
 #if defined(_MSC_VER)