Split UCI into UCIEngine and Engine

This is another refactor which aims to decouple uci from stockfish. A new engine
class manages all engine related logic and uci is a "small" wrapper around it.

In the future we should also try to remove the need for the Position object in
the uci and replace the options with an actual options struct instead of using a
map. Also convert the std::string's in the Info structs a string_view.

closes #5147

No functional change

src/engine.cpp

@@ -0,0 +1,153 @@
+/*
+  Stockfish, a UCI chess playing engine derived from Glaurung 2.1
+  Copyright (C) 2004-2024 The Stockfish developers (see AUTHORS file)
+
+  Stockfish is free software: you can redistribute it and/or modify
+  it under the terms of the GNU General Public License as published by
+  the Free Software Foundation, either version 3 of the License, or
+  (at your option) any later version.
+
+  Stockfish is distributed in the hope that it will be useful,
+  but WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+  GNU General Public License for more details.
+
+  You should have received a copy of the GNU General Public License
+  along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include "engine.h"
+
+#include <algorithm>
+#include <cassert>
+#include <cctype>
+#include <cmath>
+#include <cstdint>
+#include <cstdlib>
+#include <deque>
+#include <memory>
+#include <optional>
+#include <sstream>
+#include <vector>
+
+#include "benchmark.h"
+#include "evaluate.h"
+#include "movegen.h"
+#include "nnue/network.h"
+#include "nnue/nnue_common.h"
+#include "perft.h"
+#include "position.h"
+#include "search.h"
+#include "syzygy/tbprobe.h"
+#include "types.h"
+#include "ucioption.h"
+
+namespace Stockfish {
+
+namespace NN = Eval::NNUE;
+
+constexpr auto StartFEN = "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1";
+
+Engine::Engine(std::string path) :
+    binaryDirectory(CommandLine::get_binary_directory(path)),
+    states(new std::deque<StateInfo>(1)),
+    networks(NN::Networks(
+      NN::NetworkBig({EvalFileDefaultNameBig, "None", ""}, NN::EmbeddedNNUEType::BIG),
+      NN::NetworkSmall({EvalFileDefaultNameSmall, "None", ""}, NN::EmbeddedNNUEType::SMALL))) {
+    Tune::init(options);
+    pos.set(StartFEN, false, &states->back());
+}
+
+void Engine::go(const Search::LimitsType& limits) {
+    verify_networks();
+
+    if (limits.perft)
+    {
+        perft(pos.fen(), limits.perft, options["UCI_Chess960"]);
+        return;
+    }
+
+    threads.start_thinking(options, pos, states, limits);
+}
+void Engine::stop() { threads.stop = true; }
+
+void Engine::search_clear() {
+    wait_for_search_finished();
+
+    tt.clear(options["Threads"]);
+    threads.clear();
+
+    // @TODO wont work multiple instances
+    Tablebases::init(options["SyzygyPath"]);  // Free mapped files
+}
+
+void Engine::wait_for_search_finished() { threads.main_thread()->wait_for_search_finished(); }
+
+void Engine::set_position(const std::string& fen, const std::vector<std::string>& moves) {
+    // Drop the old state and create a new one
+    states = StateListPtr(new std::deque<StateInfo>(1));
+    pos.set(fen, options["UCI_Chess960"], &states->back());
+
+    for (const auto& move : moves)
+    {
+        auto m = UCIEngine::to_move(pos, move);
+
+        if (m == Move::none())
+            break;
+
+        states->emplace_back();
+        pos.do_move(m, states->back());
+    }
+}
+
+// modifiers
+
+void Engine::resize_threads() { threads.set({options, threads, tt, networks}); }
+
+void Engine::set_tt_size(size_t mb) {
+    wait_for_search_finished();
+    tt.resize(mb, options["Threads"]);
+}
+
+void Engine::set_ponderhit(bool b) { threads.main_manager()->ponder = b; }
+
+// network related
+
+void Engine::verify_networks() {
+    networks.big.verify(options["EvalFile"]);
+    networks.small.verify(options["EvalFileSmall"]);
+}
+
+void Engine::load_networks() {
+    networks.big.load(binaryDirectory, options["EvalFile"]);
+    networks.small.load(binaryDirectory, options["EvalFileSmall"]);
+}
+
+void Engine::load_big_network(const std::string& file) { networks.big.load(binaryDirectory, file); }
+
+void Engine::load_small_network(const std::string& file) {
+    networks.small.load(binaryDirectory, file);
+}
+
+void Engine::save_network(const std::pair<std::optional<std::string>, std::string> files[2]) {
+    networks.big.save(files[0].first);
+    networks.small.save(files[1].first);
+}
+
+// utility functions
+
+OptionsMap& Engine::get_options() { return options; }
+
+uint64_t Engine::nodes_searched() const { return threads.nodes_searched(); }
+
+void Engine::trace_eval() {
+    StateListPtr trace_states(new std::deque<StateInfo>(1));
+    Position     p;
+    p.set(pos.fen(), options["UCI_Chess960"], &trace_states->back());
+
+    verify_networks();
+
+    sync_cout << "\n" << Eval::trace(p, networks) << sync_endl;
+}
+
+}