Allow command line parameters for engines (to support lc0 backend selection)

Author: domschl

README.md

@@ -95,6 +95,17 @@ A sample content for stockfish in Linux would be:
 }
 ```
 
+An example for `lc0` (Leela Chess Zero) with CUDA backend:
+
+```json
+  "name": "lc0",
+  "path": "/home/user/lc0/build/release/lc0",
+  "engine_params": ["--backend=cuda"],
+  "active": true
+```
+
+Note: The field "engine_params" is optional and can contain a list of additional parameters for the engine that are given on start.
+
 Note: Windows users need to use paths with `\\` or `/` for proper json encoding.
 
 ### Start
@@ -142,7 +153,7 @@ Do NOT use `sudo` on subsequent starts, or the communication might fail. If scan
 
 All engine descriptions in directory 'engines' will now contain the default-UCI options for each engine. Those can be edited e.g. to enable tablebases or other UCI options.
 
-![Console mchess](https://raw.github.com/domschl/python-mchess/master/images/MchessAlpha.png)
+![Console mchess](https://raw.github.com/domschl/python-mchess/master/images/TurquoiseAlpha.png)
 _Console output of python module, allows terminal interactions: enter 'help' for an overview of console commands_
 
 ## Usage
@@ -215,6 +226,7 @@ The mandatory fields in `<engine-name>.json` are:
 | -------- | --------------------------------- | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
 | `name`   | e.g. `"stockfish"`                | Name of executable of the engine, e.g. `stockfish`. Unfortunately this name must be precisely equal to the name of the json file, and must be referenced in `preferences.json` as either `computer_player_name` or `computer_player2_name` and within `active_agents`. That is subject to improvement in the future. |
 | `path`   | e.g. `"/usr/local/bin/stockfish"` | Path to the engine executable. Windows users must either use `\\` or `/` in json files as path separators.                                                                                                                                                                                                           |
+| `engine_params` | `["--backend=cuda"]` | Optional list of additional parameters for the engine that are given on start. This entry should be ommited, if no parameter are necessary. |
 | `active` | `true`                            | `mchess.py` currently uses only the first two active engines. If more engines are configured, the unused ones should be set to `false`                                                                                                                                                                               |
 
 Once the UCI engine is started for the first time, the UCI-options of the engine are enumerated and added to the `<engine-name>.json` config file. That allows further customization of each engine. Some commonly used options are:

images/TurquoiseAlpha.png

@@ -180,8 +180,11 @@ def send_agent_state(self, state, msg=""):
 
     async def uci_open_engine(self):
         try:
-            transport, engine = await chess.engine.popen_uci(
-                self.engine_json['path'])
+            if 'engine_params' in self.engine_json:
+                engine_path = [self.engine_json['path']] + self.engine_json['engine_params']
+            else:
+                engine_path = self.engine_json['path']
+            transport, engine = await chess.engine.popen_uci(engine_path)
             self.engine = engine
             self.transport = transport
             self.log.info(f"Engine {self.name} opened.")
@@ -344,8 +347,11 @@ async def async_go(self, board, mtime, ponder=False, analysis=False):
                             #     sc = str(info['score'])
                             # else:
                             #     cp = float(str(info['score']))/100.0
-                            #     sc = '{:.2f}'.format(cp)
-                            sc = info['score'].relative.score(mate_score=10000) / 100.0
+                            #     sc = '{:.2f}'.format(cp) 
+                            if info['score'].is_mate():
+                                sc = f"#{info['score'].relative.mate()}"
+                            else:
+                                sc = info['score'].relative.score(mate_score=10000) / 100.0
                         except Exception as e:
                             self.log.error(
                                 f"Score transform failed {info['score']}: {e}")