Remove uithread

With the current questions and issues around threading, I had a look at
https://github.com/official-stockfish/Stockfish/issues/2299.

It seems there was a problem with data races when requesting eval via UCI while
a search was already running. To fix this an extra thread uithread was created,
presumably to avoid an overlap with Threads.main() that was causing problems.
Making this eval request seems to be outside the scope of UCI, and @vondele also
reports that the data race is not even fixed reliably by this change. I suggest
we simplify the threading here by removing this uithread and adding a comment
signaling that user should not request eval when a search is already running.

Closes https://github.com/official-stockfish/Stockfish/pull/2310

No functional change.

diff --git a/src/uci.cpp b/src/uci.cpp
index a4235f2b23fb601c535f91c33f4d7c1b0ab36f77..99bf1a13fa729c673e7883de3782522a6f7848c9 100644 (file)
--- a/src/uci.cpp
+++ b/src/uci.cpp
@@ -191,9 +191,8 @@ void UCI::loop(int argc, char* argv[]) {
   Position pos;
   string token, cmd;
   StateListPtr states(new std::deque<StateInfo>(1));
-  auto uiThread = std::make_shared<Thread>(0);
 
-  pos.set(StartFEN, false, &states->back(), uiThread.get());
+  pos.set(StartFEN, false, &states->back(), Threads.main());
 
   for (int i = 1; i < argc; ++i)
       cmd += std::string(argv[i]) + " ";
@@ -229,7 +228,8 @@ void UCI::loop(int argc, char* argv[]) {
       else if (token == "ucinewgame") Search::clear();
       else if (token == "isready")    sync_cout << "readyok" << sync_endl;
 
-      // Additional custom non-UCI commands, mainly for debugging
+      // Additional custom non-UCI commands, mainly for debugging.
+      // Do not use these commands during a search!
       else if (token == "flip")  pos.flip();
       else if (token == "bench") bench(pos, is, states);
       else if (token == "d")     sync_cout << pos << sync_endl;