Minimal support for FRC in the data generator. (#4049)

Allows UCI_Chess960 to be true during data generation.
If UCI_Chess960 is true then strips castling rights from all saved
positions and skips saving positions with castling move.
UCI_Chess960 is respected in transforms.

src/position.cpp

@@ -1370,15 +1370,15 @@ bool Position::pos_is_ok() const {
 // Add a function that directly unpacks for speed. It's pretty tough.
 // Write it by combining packer::unpack() and Position::set().
 // If there is a problem with the passed phase and there is an error, non-zero is returned.
-int Position::set_from_packed_sfen(const Tools::PackedSfen& sfen , StateInfo* si, Thread* th)
+int Position::set_from_packed_sfen(const Tools::PackedSfen& sfen , StateInfo* si, Thread* th, bool frc)
 {
-  return Tools::set_from_packed_sfen(*this, sfen, si, th);
+  return Tools::set_from_packed_sfen(*this, sfen, si, th, frc);
 }
 
 // Get the packed sfen. Returns to the buffer specified in the argument.
-void Position::sfen_pack(Tools::PackedSfen& sfen)
+void Position::sfen_pack(Tools::PackedSfen& sfen, bool resetCastlingRights)
 {
-  sfen = Tools::sfen_pack(*this);
+  sfen = Tools::sfen_pack(*this, resetCastlingRights);
 }
 
 } // namespace Stockfish

src/position.h

@@ -179,17 +179,17 @@ public:
 
   // --sfenization helper
 
-  friend int Tools::set_from_packed_sfen(Position& pos, const Tools::PackedSfen& sfen, StateInfo* si, Thread* th);
+  friend int Tools::set_from_packed_sfen(Position& pos, const Tools::PackedSfen& sfen, StateInfo* si, Thread* th, bool frc);
 
   // Get the packed sfen. Returns to the buffer specified in the argument.
   // Do not include gamePly in pack.
-  void sfen_pack(Tools::PackedSfen& sfen);
+  void sfen_pack(Tools::PackedSfen& sfen, bool resetCastlingRights);
 
   // It is slow to go through sfen, so I made a function to set packed sfen directly.
   // Equivalent to pos.set(sfen_unpack(data),si,th);.
   // If there is a problem with the passed phase and there is an error, non-zero is returned.
   // PackedSfen does not include gamePly so it cannot be restored. If you want to set it, specify it with an argument.
-  int set_from_packed_sfen(const Tools::PackedSfen& sfen, StateInfo* si, Thread* th);
+  int set_from_packed_sfen(const Tools::PackedSfen& sfen, StateInfo* si, Thread* th, bool frc);
 
   void clear() { std::memset(this, 0, sizeof(Position)); }
 

src/tools/convert.cpp

@@ -103,7 +103,7 @@ namespace Stockfish::Tools
                         filtered_size_fen++;
                     }
                     else {
-                        tpos.sfen_pack(p.sfen);
+                        tpos.sfen_pack(p.sfen, false);
                     }
                 }
                 else if (token == "move") {
@@ -337,7 +337,7 @@ namespace Stockfish::Tools
 
                                     StateInfo si;
                                     pos.set(str_fen, false, &si, th);
-                                    pos.sfen_pack(psv.sfen);
+                                    pos.sfen_pack(psv.sfen, false);
                                 }
 
 #if defined(DEBUG_CONVERT_BIN_FROM_PGN_EXTRACT)
@@ -478,7 +478,7 @@ namespace Stockfish::Tools
             {
                 if (fs.read((char*)&p, sizeof(PackedSfenValue))) {
                     StateInfo si;
-                    tpos.set_from_packed_sfen(p.sfen, &si, th);
+                    tpos.set_from_packed_sfen(p.sfen, &si, th, false);
 
                     // write as plain text
                     ofs << "fen " << tpos.fen() << std::endl;

src/tools/sfen_packer.cpp

@@ -94,7 +94,7 @@ namespace Stockfish::Tools {
     //
     struct SfenPacker
     {
-        void pack(const Position& pos);
+        void pack(const Position& pos, bool resetCastlingRights);
 
         // sfen packed by pack() (256bit = 32bytes)
         // Or sfen to decode with unpack()
@@ -149,7 +149,7 @@ namespace Stockfish::Tools {
     };
 
     // Pack sfen and store in data[32].
-    void SfenPacker::pack(const Position& pos)
+    void SfenPacker::pack(const Position& pos, bool resetCastlingRights)
     {
         memset(data, 0, 32 /* 256bit */);
         stream.set_data(data);
@@ -175,11 +175,17 @@ namespace Stockfish::Tools {
             }
         }
 
-        // TODO(someone): Support chess960.
+        if (resetCastlingRights)
+        {
+            stream.write_n_bit(0, 4);
+        }
+        else
+        {
             stream.write_one_bit(pos.can_castle(WHITE_OO));
             stream.write_one_bit(pos.can_castle(WHITE_OOO));
             stream.write_one_bit(pos.can_castle(BLACK_OO));
             stream.write_one_bit(pos.can_castle(BLACK_OOO));
+        }
 
         if (pos.ep_square() == SQ_NONE) {
             stream.write_one_bit(0);
@@ -249,7 +255,7 @@ namespace Stockfish::Tools {
         return make_piece(c, pr);
     }
 
-    int set_from_packed_sfen(Position& pos, const PackedSfen& sfen, StateInfo* si, Thread* th)
+    int set_from_packed_sfen(Position& pos, const PackedSfen& sfen, StateInfo* si, Thread* th, bool frc)
     {
         SfenPacker packer;
         auto& stream = packer.stream;
@@ -304,7 +310,6 @@ namespace Stockfish::Tools {
         }
 
         // Castling availability.
-        // TODO(someone): Support chess960.
         pos.st->castlingRights = 0;
         if (stream.read_one_bit()) {
             Square rsq;
@@ -362,7 +367,7 @@ namespace Stockfish::Tools {
 
         assert(stream.get_cursor() <= 256);
 
-        pos.chess960 = false;
+        pos.chess960 = frc;
         pos.thisThread = th;
         pos.set_state(pos.st);
 
@@ -371,13 +376,13 @@ namespace Stockfish::Tools {
         return 0;
     }
 
-    PackedSfen sfen_pack(Position& pos)
+    PackedSfen sfen_pack(Position& pos, bool resetCastlingRights)
     {
         PackedSfen sfen;
 
         SfenPacker sp;
         sp.data = (uint8_t*)&sfen;
-        sp.pack(pos);
+        sp.pack(pos, resetCastlingRights);
 
         return sfen;
     }

src/tools/sfen_packer.h

@@ -15,8 +15,8 @@ namespace Stockfish {
 
 namespace Stockfish::Tools {
 
-    int set_from_packed_sfen(Position& pos, const PackedSfen& sfen, StateInfo* si, Thread* th);
+    int set_from_packed_sfen(Position& pos, const PackedSfen& sfen, StateInfo* si, Thread* th, bool frc);
-    PackedSfen sfen_pack(Position& pos);
+    PackedSfen sfen_pack(Position& pos, bool resetCastlingRights);
 }
 
 #endif

src/tools/stats.cpp

@@ -1192,6 +1192,7 @@ namespace Stockfish::Tools::Stats
         Thread* th = Threads.main();
         Position& pos = th->rootPos;
         StateInfo si;
+        const bool frc = Options["UCI_Chess960"];
 
         auto in = Tools::open_sfen_input_file(filename);
 
@@ -1214,7 +1215,7 @@ namespace Stockfish::Tools::Stats
 
             auto& psv = v.value();
 
-            pos.set_from_packed_sfen(psv.sfen, &si, th);
+            pos.set_from_packed_sfen(psv.sfen, &si, th, frc);
 
             on_entry(pos, (Move)psv.move, psv);
 

src/tools/training_data_generator.cpp

@@ -271,6 +271,7 @@ namespace Stockfish::Tools
 
         const auto start_time = now();
 
+        const bool frc = Options["UCI_Chess960"];
         // repeat until the specified number of times
         while (!quit)
         {
@@ -286,11 +287,11 @@ namespace Stockfish::Tools
             if (opening_book != nullptr)
             {
                 auto& fen = opening_book->next_fen();
-                pos.set(fen, false, &si, &th);
+                pos.set(fen, frc, &si, &th);
             }
             else
             {
-                pos.set(StartFEN, false, &si, &th);
+                pos.set(StartFEN, frc, &si, &th);
             }
 
             int resign_counter = 0;
@@ -367,7 +368,7 @@ namespace Stockfish::Tools
 
                     // Here we only write the position data.
                     // Result is added after the whole game is done.
-                    pos.sfen_pack(psv.sfen);
+                    pos.sfen_pack(psv.sfen, pos.is_chess960());
 
                     psv.score = search_value;
                     psv.move = search_pv[0];
@@ -695,9 +696,17 @@ namespace Stockfish::Tools
             it->game_result = side_to_move == result_color ? result : -result;
         }
 
+        const bool frc = th.rootPos.is_chess960();
         // Write sfens in move order to make potential compression easier
         for (auto& sfen : sfens)
         {
+            // Skip positions with castling bestmove in FRC so that we don't
+            // need to support it in the trainer.
+            if (frc && type_of((Move)sfen.move) == CASTLING)
+            {
+                continue;
+            }
+
             // Return true if there is already enough data generated.
             const auto iter = counter.fetch_add(1);
             if (iter >= limit)
@@ -858,7 +867,6 @@ namespace Stockfish::Tools
             else if (token == "set_recommended_uci_options")
             {
                 UCI::setoption("Skill Level", "20");
-                UCI::setoption("UCI_Chess960", "false");
                 UCI::setoption("UCI_LimitStrength", "false");
                 UCI::setoption("PruneAtShallowDepth", "false");
                 UCI::setoption("EnableTranspositionTable", "true");

src/tools/training_data_generator_nonpv.cpp

@@ -204,23 +204,24 @@ namespace Stockfish::Tools
             if ((double)prng.rand<uint64_t>() / std::numeric_limits<uint64_t>::max() < params.exploration_save_rate)
             {
                 psv.emplace_back();
-                pos.sfen_pack(psv.back().sfen);
+                pos.sfen_pack(psv.back().sfen, pos.is_chess960());
             }
         });
 
         auto& pos = th.rootPos;
         StateInfo si;
 
+        const bool frc = Options["UCI_Chess960"];
         for (int i = 0; i < count; ++i)
         {
             if (opening_book != nullptr)
             {
                 auto& fen = opening_book->next_fen();
-                pos.set(fen, false, &si, &th);
+                pos.set(fen, frc, &si, &th);
             }
             else
             {
-                pos.set(StartFEN, false, &si, &th);
+                pos.set(StartFEN, frc, &si, &th);
             }
 
             for(int ply = 0; ply < params.exploration_max_ply; ++ply)
@@ -267,6 +268,7 @@ namespace Stockfish::Tools
         // end flag
         bool quit = false;
 
+        const bool frc = Options["UCI_Chess960"];
         // repeat until the specified number of times
         while (!quit)
         {
@@ -280,7 +282,7 @@ namespace Stockfish::Tools
 
             for (auto& ps : packed_sfens)
             {
-                pos.set_from_packed_sfen(ps.sfen, &si, &th);
+                pos.set_from_packed_sfen(ps.sfen, &si, &th, frc);
                 pos.state()->rule50 = 0;
 
                 if (params.smart_fen_skipping && pos.checkers())
@@ -306,7 +308,7 @@ namespace Stockfish::Tools
                 }
 
                 auto& new_ps = psv.emplace_back();
-                pos.sfen_pack(new_ps.sfen);
+                pos.sfen_pack(new_ps.sfen, pos.is_chess960());
                 new_ps.score = search_value;
                 new_ps.move = search_pv[0];
                 new_ps.gamePly = 1;
@@ -329,9 +331,17 @@ namespace Stockfish::Tools
         std::atomic<uint64_t>& counter,
         uint64_t limit)
     {
+        const bool frc = th.rootPos.is_chess960();
         // Write sfens in move order to make potential compression easier
         for (auto& sfen : sfens)
         {
+            // Skip positions with castling bestmove in FRC so that we don't
+            // need to support it in the trainer.
+            if (frc && type_of((Move)sfen.move) == CASTLING)
+            {
+                continue;
+            }
+
             // Return true if there is already enough data generated.
             const auto iter = counter.fetch_add(1);
             if (iter >= limit)
@@ -435,7 +445,6 @@ namespace Stockfish::Tools
             else if (token == "set_recommended_uci_options")
             {
                 UCI::setoption("Skill Level", "20");
-                UCI::setoption("UCI_Chess960", "false");
                 UCI::setoption("UCI_LimitStrength", "false");
                 UCI::setoption("PruneAtShallowDepth", "false");
                 UCI::setoption("EnableTranspositionTable", "true");

src/tools/transform.cpp

@@ -140,6 +140,7 @@ namespace Stockfish::Tools
 
         buffer.reserve(batch_size);
 
+        const bool frc = Options["UCI_Chess960"];
         uint64_t num_processed = 0;
         for (;;)
         {
@@ -149,7 +150,7 @@ namespace Stockfish::Tools
 
             auto& ps = v.value();
 
-            pos.set_from_packed_sfen(ps.sfen, &si, th);
+            pos.set_from_packed_sfen(ps.sfen, &si, th, frc);
             auto static_eval = Eval::evaluate(pos);
             auto deep_eval = ps.score;
             ps.score = nudge(params, static_eval, deep_eval);
@@ -290,6 +291,7 @@ namespace Stockfish::Tools
         Threads.execute_with_workers([&](auto& th){
             Position& pos = th.rootPos;
             StateInfo si;
+            const bool frc = Options["UCI_Chess960"];
 
             for(;;)
             {
@@ -297,7 +299,7 @@ namespace Stockfish::Tools
                 if (!fen.has_value())
                     return;
 
-                pos.set(*fen, false, &si, &th);
+                pos.set(*fen, frc, &si, &th);
                 pos.state()->rule50 = 0;
 
 
@@ -310,7 +312,7 @@ namespace Stockfish::Tools
                     continue;
 
                 PackedSfenValue ps;
-                pos.sfen_pack(ps.sfen);
+                pos.sfen_pack(ps.sfen, pos.is_chess960());
                 ps.score = search_value;
                 ps.move = search_pv[0];
                 ps.gamePly = 1;
@@ -401,6 +403,7 @@ namespace Stockfish::Tools
         Threads.execute_with_workers([&](auto& th){
             Position& pos = th.rootPos;
             StateInfo si;
+            const bool frc = Options["UCI_Chess960"];
 
             for (;;)
             {
@@ -410,7 +413,7 @@ namespace Stockfish::Tools
 
                 for(auto& ps : psv)
                 {
-                    pos.set_from_packed_sfen(ps.sfen, &si, &th);
+                    pos.set_from_packed_sfen(ps.sfen, &si, &th, frc);
 
                     for (int cnt = 0; cnt < params.research_count; ++cnt)
                         Search::search(pos, params.depth, 1);
@@ -420,7 +423,7 @@ namespace Stockfish::Tools
                     if (search_pv.empty())
                         continue;
 
-                    pos.sfen_pack(ps.sfen);
+                    pos.sfen_pack(ps.sfen, false);
                     ps.score = search_value;
                     if (!params.keep_moves)
                         ps.move = search_pv[0];