Fix some races and clarify the code

Better split code that should be run at
startup from code run at ucinewgame. Also
fix several races when 'bench', 'perft' and
'ucinewgame' are sent just after 'bestomve'
from the engine threads are still running.

Also use a specific UI thread instead of
main thread when setting up the Position
object used by UI uci loop. This fixes a
race when sending 'eval' command while searching.

We accept a race on 'setoption' to allow the
GUI to change an option while engine is searching
withouth stalling the pipe. Note that changing an
option while searchingg is anyhow not mandated by
UCI protocol.

No functional change.

src/benchmark.cpp

@@ -109,9 +109,9 @@ void benchmark(const Position& current, istream& is) {
   string fenFile   = (is >> token) ? token : "default";
   string limitType = (is >> token) ? token : "depth";
 
-  Options["Hash"]    = ttSize;
+  Search::clear(); // Wait for search finished
   Options["Threads"] = threads;
-  Search::clear();
+  Options["Hash"]    = ttSize;
 
   if (limitType == "time")
       limits.movetime = stoi(limit); // movetime is in millisecs

src/main.cpp

@@ -24,6 +24,7 @@
 #include "position.h"
 #include "search.h"
 #include "thread.h"
+#include "tt.h"
 #include "uci.h"
 #include "syzygy/tbprobe.h"
 
@@ -42,7 +43,10 @@ int main(int argc, char* argv[]) {
   Bitbases::init();
   Search::init();
   Pawns::init();
+  Tablebases::init(Options["SyzygyPath"]);
+  TT.resize(Options["Hash"]);
   Threads.init();
+  Search::clear(); // After threads are up
 
   UCI::loop(argc, argv);
 

src/search.cpp

@@ -183,10 +183,13 @@ void Search::init() {
 }
 
 
-/// Search::clear() resets search state to its initial value, to obtain reproducible results
+/// Search::clear() resets search state to its initial value
 
 void Search::clear() {
 
+  Threads.main()->wait_for_search_finished();
+
+  Time.availableNodes = 0;
   TT.clear();
 
   for (Thread* th : Threads)

src/uci.cpp

@@ -138,15 +138,6 @@ namespace {
     Threads.start_thinking(pos, States, limits);
   }
 
-  // On ucinewgame following steps are needed to reset the state
-  void newgame() {
-
-    TT.resize(Options["Hash"]);
-    Search::clear();
-    Tablebases::init(Options["SyzygyPath"]);
-    Time.availableNodes = 0;
-  }
-
 } // namespace
 
 
@@ -160,10 +151,9 @@ void UCI::loop(int argc, char* argv[]) {
 
   Position pos;
   string token, cmd;
+  Thread* uiThread = new Thread();
 
-  newgame(); // Implied ucinewgame before the first position command
-
-  pos.set(StartFEN, false, &States->back(), Threads.main());
+  pos.set(StartFEN, false, &States->back(), uiThread);
 
   for (int i = 1; i < argc; ++i)
       cmd += std::string(argv[i]) + " ";
@@ -197,7 +187,7 @@ void UCI::loop(int argc, char* argv[]) {
                     << "\n"       << Options
                     << "\nuciok"  << sync_endl;
 
-      else if (token == "ucinewgame") newgame();
+      else if (token == "ucinewgame") Search::clear();
       else if (token == "isready")    sync_cout << "readyok" << sync_endl;
       else if (token == "go")         go(pos, is);
       else if (token == "position")   position(pos, is);
@@ -225,6 +215,7 @@ void UCI::loop(int argc, char* argv[]) {
   } while (token != "quit" && argc == 1); // Passed args have one-shot behaviour
 
   Threads.main()->wait_for_search_finished();
+  delete uiThread;
 }