Rework perft implementation

Unify various perft functions and move all the code
to search.cpp.

Avoid perft implementation to be splitted between
benchmark.cpp (where it has no reason to be) and
search.cpp

No functional and no speed change (tested).

src/benchmark.cpp

@@ -139,15 +139,8 @@ void benchmark(const Position& current, istream& is) {
       cerr << "\nPosition: " << i + 1 << '/' << fens.size() << endl;
 
       if (limitType == "perft")
-          for (MoveList<LEGAL> it(pos); *it; ++it)
+          nodes += Search::perft<true>(pos, limits.depth * ONE_PLY);
-          {
+
-              StateInfo si;
-              pos.do_move(*it, si);
-              uint64_t cnt = limits.depth > 1 ? Search::perft(pos, (limits.depth - 1) * ONE_PLY) : 1;
-              pos.undo_move(*it);
-              cout << move_to_uci(*it, pos.is_chess960()) << ": " << cnt << endl;
-              nodes += cnt;
-          }
       else
       {
           Threads.start_thinking(pos, limits, st);

src/search.cpp

@@ -152,26 +152,33 @@ void Search::init() {
 
 /// Search::perft() is our utility to verify move generation. All the leaf nodes
 /// up to the given depth are generated and counted and the sum returned.
-
+template<bool Root>
-static uint64_t perft(Position& pos, Depth depth) {
+uint64_t Search::perft(Position& pos, Depth depth) {
 
   StateInfo st;
-  uint64_t cnt = 0;
+  uint64_t cnt, nodes = 0;
   CheckInfo ci(pos);
   const bool leaf = depth == 2 * ONE_PLY;
 
   for (MoveList<LEGAL> it(pos); *it; ++it)
+  {
+      if (Root && depth <= ONE_PLY)
+          cnt = 1;
+      else
       {
           pos.do_move(*it, st, ci, pos.gives_check(*it, ci));
-      cnt += leaf ? MoveList<LEGAL>(pos).size() : ::perft(pos, depth - ONE_PLY);
+          cnt = leaf ? MoveList<LEGAL>(pos).size() : perft<false>(pos, depth - ONE_PLY);
+          nodes += cnt;
           pos.undo_move(*it);
       }
-  return cnt;
+      if (Root)
+          sync_cout << move_to_uci(*it, pos.is_chess960()) << ": " << cnt << sync_endl;
+  }
+  return nodes;
 }
 
-uint64_t Search::perft(Position& pos, Depth depth) {
+template uint64_t Search::perft<true>(Position& pos, Depth depth);
-  return depth > ONE_PLY ? ::perft(pos, depth) : MoveList<LEGAL>(pos).size();
+
-}
 
 /// Search::think() is the external interface to Stockfish's search, and is
 /// called by the main thread when the program receives the UCI 'go' command. It

src/search.h

@@ -105,8 +105,8 @@ extern Time::point SearchTime;
 extern StateStackPtr SetupStates;
 
 extern void init();
-extern uint64_t perft(Position& pos, Depth depth);
 extern void think();
+template<bool Root> uint64_t perft(Position& pos, Depth depth);
 
 } // namespace Search