Stockfish NNUE file not loading in ChessKitEngine

[avadhesh18]

I am using ChessKitEngine to integrate Stockfish into my iOS app. I have added the nn-1111cefa1111.nnue file to my project's root folder and included it in the targets. The file was downloaded from the official Stockfish website, and I have not renamed it.

Issue

No matter how I specify the NNUE file (filename, full path, escaped spaces, etc.), the engine always fails to load it and crashes.

My Code

import Foundation
import ChessKitEngine

final class StockfishEngine {
    static let shared = StockfishEngine()
    private let engine = Engine(type: .stockfish)
    private var isReady = false
    private var pendingCompletionHandlers: [(String?) -> Void] = []

    init() {
        startEngine()
    }

    func startEngine() {
        print("Starting engine initialization...")
        engine.loggingEnabled = true
        engine.start {
            self.engine.send(command: .uci)
            
            // Attempting to set the NNUE file
            self.engine.send(command: .setoption(id: "EvalFile", value: "nn-1111cefa1111.nnue"))
            
            let threadCount = min(ProcessInfo.processInfo.processorCount - 1, 7)
            self.engine.send(command: .setoption(id: "Threads", value: String(threadCount)))
            self.engine.send(command: .setoption(id: "Skill Level", value: "10"))
            
            self.engine.send(command: .isready)
            
            self.engine.receiveResponse = { response in
                if "\(response)".contains("readyok") {
                    self.isReady = true
                    print("Stockfish Engine Started!")
                    self.processPendingRequests()
                    self.setupMoveResponseHandler()
                }
            }
        }
    }
}

Error Log

Starting engine initialization...
uci
Stockfish 17 by the Stockfish developers (see AUTHORS file)
minemine
x
<id> <name> Stockfish 17
<id> <author> the Stockfish developers (see AUTHORS file)
option name Debug Log File type string default <empty>
option name Clear Hash type button
option name Ponder type check default false
option name EvalFile type string default nn-1111cefa1111.nnue
option name EvalFileSmall type string default nn-37f18f62d772.nnue
<uciok>
isready
<readyok>
setoption name EvalFile value /Users/myname/Library/Developer/CoreSimulator/Devices/D1F042AC-7361-4EBC-86B7-6FA9050F68A9/data/Containers/Bundle/Application/885F453B-3219-475A-9786-14C7DF2BFBB1/App%20Name.app/nn-1111cefa1111.nnue
setoption name Threads value 7
setoption name MultiPV value 1
uci
setoption name EvalFile value nn-1111cefa1111.nnue
setoption name Threads value 7
setoption name Skill Level value 10
isready
Stockfish Engine Started!
<info> <string> Using 7 threads
<id> <name> Stockfish 17
<id> <author> the Stockfish developers (see AUTHORS file)
option name Debug Log File type string default <empty>
option name EvalFile type string default nn-1111cefa1111.nnue
option name EvalFileSmall type string default nn-37f18f62d772.nnue
<uciok>
<info> <string> Using 7 threads
<readyok>
setoption name Skill Level value 0
ucinewgame
position fen rnbqkbnr/pppppppp/8/8/8/3P4/PPP1PPPP/RNBQKBNR b KQkq - 0 1
go depth 15
rnbqkbnr/pppppppp/8/8/8/3P4/PPP1PPPP/RNBQKBNR b KQkq - 0 1
<info> <string> Available processors: 0-7
<info> <string> Using 7 threads
<info> <string> ERROR: Network evaluation parameters compatible with the engine must be available.
<info> <string> ERROR: The network file nn-1111cefa1111.nnue was not loaded successfully.
<info> <string> ERROR:
The UCI option EvalFile might need to specify the full path, including the directory name, to the network file.
<info> <string> ERROR: The default net can be downloaded from: https://tests.stockfishchess.org/api/nn/nn-1111cefa1111.nnue
<info> <string> ERROR: The engine will be terminated now.

What I Have Tried

• Specifying just the filename: "nn-1111cefa1111.nnue"
• Using the full path:

  let path = Bundle.main.path(forResource: "nn-1111cefa1111", ofType: "nnue")
  self.engine.send(command: .setoption(id: "EvalFile", value: path ?? ""))

• Escaping spaces in the path
• Verifying the file exists in the app bundle

Still, nothing seems to work. How can I correctly load the NNUE file for Stockfish using ChessKitEngine? I am honestly out of ideas at this point. Is it because my app name contains spaces?

[fellowgeek]

Hey! Just wanted to let you know that you probably don't need to manually set the NNUE files.

It looks like as long as nn-37f18f62d772.nnue and nn-1111cefa1111.nnue are in the app bundle, the engine should automatically find them when the engine type is set to Stockfish.

You can see this in the code here on line 39.

Cheers!

[avadhesh18]

Yeah it does but if your xcode project name has spaces in it no matter what you do it doesn't work.

[fellowgeek]

Yes just confirmed! I see in your fork you done something to fix it... I am playing with a chess game so I might use your fork.

[avadhesh18]

Well even that didn't work, I had to create a new project without spaces. Also you need both the files, just adding the smaller one won't work.