Send error message as an UCI info string

some GUIs do not show the error message when the engine terminates in the no-net case, as it is send to cerr.
Instead send it as an info string, which the GUI will more likely display.

closes https://github.com/official-stockfish/Stockfish/pull/3031

No functional change.

diff --git a/src/evaluate.cpp b/src/evaluate.cpp
index 1bd893533bb082f0d9a006d8c5cd22f764c5b619..c84d894f9c86616787e6f2a86c327035d115e407 100644 (file)
--- a/src/evaluate.cpp
+++ b/src/evaluate.cpp
@@ -53,10 +53,11 @@ namespace Eval {
         UCI::OptionsMap defaults;
         UCI::init(defaults);
 
-        std::cerr << "NNUE evaluation used, but the network file " << eval_file << " was not loaded successfully. "
-                  << "These network evaluation parameters must be available, and compatible with this version of the code. "
-                  << "The UCI option EvalFile might need to specify the full path, including the directory/folder name, to the file. "
-                  << "The default net can be downloaded from: https://tests.stockfishchess.org/api/nn/"+std::string(defaults["EvalFile"]) << std::endl;
+        sync_cout << "info string ERROR: NNUE evaluation used, but the network file " << eval_file << " was not loaded successfully." << sync_endl;
+        sync_cout << "info string ERROR: The UCI option EvalFile might need to specify the full path, including the directory/folder name, to the file." << sync_endl;
+        sync_cout << "info string ERROR: The default net can be downloaded from: https://tests.stockfishchess.org/api/nn/"+std::string(defaults["EvalFile"]) << sync_endl;
+        sync_cout << "info string ERROR: If the UCI option Use NNUE is set to true, network evaluation parameters compatible with the program must be available." << sync_endl;
+        sync_cout << "info string ERROR: The engine will be terminated now." << sync_endl;
         std::exit(EXIT_FAILURE);
     }