attempt 2 at preparing for strict concurrency (#90)

* attempt 2 at preparing for strict concurrency

- see also #83
- this marks many things in Sendable (which I think we can take regardless)
- creates an actor container for models and tokenizers, which are not Sendable (though perhaps Tokenizers could be)

Applications/LLMEval/ContentView.swift

@@ -148,9 +148,9 @@ struct ContentView: View {
 }
 
 @Observable
+@MainActor
 class LLMEvaluator {
 
-    @MainActor
     var running = false
 
     var output = ""
@@ -172,91 +172,87 @@ class LLMEvaluator {
 
     enum LoadState {
         case idle
-        case loaded(LLMModel, Tokenizers.Tokenizer)
+        case loaded(ModelContainer)
     }
 
     var loadState = LoadState.idle
 
     /// load and return the model -- can be called multiple times, subsequent calls will
     /// just return the loaded model
-    func load() async throws -> (LLMModel, Tokenizers.Tokenizer) {
+    func load() async throws -> ModelContainer {
         switch loadState {
         case .idle:
             // limit the buffer cache
             MLX.GPU.set(cacheLimit: 20 * 1024 * 1024)
 
-            let (model, tokenizer) = try await LLM.load(configuration: modelConfiguration) {
+            let modelContainer = try await LLM.loadModelContainer(configuration: modelConfiguration)
+            {
                 [modelConfiguration] progress in
-                DispatchQueue.main.sync {
+                Task { @MainActor in
                     self.modelInfo =
                         "Downloading \(modelConfiguration.name): \(Int(progress.fractionCompleted * 100))%"
                 }
             }
             self.modelInfo =
                 "Loaded \(modelConfiguration.id).  Weights: \(MLX.GPU.activeMemory / 1024 / 1024)M"
-            loadState = .loaded(model, tokenizer)
-            return (model, tokenizer)
+            loadState = .loaded(modelContainer)
+            return modelContainer
 
-        case .loaded(let model, let tokenizer):
-            return (model, tokenizer)
+        case .loaded(let modelContainer):
+            return modelContainer
         }
     }
 
     func generate(prompt: String) async {
-        let canGenerate = await MainActor.run {
-            if running {
-                return false
-            } else {
-                running = true
-                self.output = ""
-                return true
-            }
-        }
+        guard !running else { return }
 
-        guard canGenerate else { return }
+        running = true
+        self.output = ""
 
         do {
-            let (model, tokenizer) = try await load()
+            let modelContainer = try await load()
+
             // augment the prompt as needed
             let prompt = modelConfiguration.prepare(prompt: prompt)
-            let promptTokens = tokenizer.encode(text: prompt)
+
+            let promptTokens = await modelContainer.perform { _, tokenizer in
+                tokenizer.encode(text: prompt)
+            }
 
             // each time you generate you will get something new
             MLXRandom.seed(UInt64(Date.timeIntervalSinceReferenceDate * 1000))
 
-            let result = await LLM.generate(
-                promptTokens: promptTokens, parameters: generateParameters, model: model,
-                tokenizer: tokenizer, extraEOSTokens: modelConfiguration.extraEOSTokens
-            ) { tokens in
-                // update the output -- this will make the view show the text as it generates
-                if tokens.count % displayEveryNTokens == 0 {
-                    let text = tokenizer.decode(tokens: tokens)
-                    await MainActor.run {
-                        self.output = text
+            let result = await modelContainer.perform { model, tokenizer in
+                LLM.generate(
+                    promptTokens: promptTokens, parameters: generateParameters, model: model,
+                    tokenizer: tokenizer, extraEOSTokens: modelConfiguration.extraEOSTokens
+                ) { tokens in
+                    // update the output -- this will make the view show the text as it generates
+                    if tokens.count % displayEveryNTokens == 0 {
+                        let text = tokenizer.decode(tokens: tokens)
+                        Task { @MainActor in
+                            self.output = text
+                        }
                     }
-                }
 
-                if tokens.count >= maxTokens {
-                    return .stop
-                } else {
-                    return .more
+                    if tokens.count >= maxTokens {
+                        return .stop
+                    } else {
+                        return .more
+                    }
                 }
             }
 
             // update the text if needed, e.g. we haven't displayed because of displayEveryNTokens
-            await MainActor.run {
-                if result.output != self.output {
-                    self.output = result.output
-                }
-                running = false
-                self.stat = " Tokens/second: \(String(format: "%.3f", result.tokensPerSecond))"
+            if result.output != self.output {
+                self.output = result.output
             }
+            self.stat = " Tokens/second: \(String(format: "%.3f", result.tokensPerSecond))"
 
         } catch {
-            await MainActor.run {
-                running = false
-                output = "Failed: \(error)"
-            }
+            output = "Failed: \(error)"
         }
+
+        running = false
     }
 }

Applications/LLMEval/ViewModels/DeviceStat.swift

@@ -3,33 +3,22 @@ import LLM
 import MLX
 
 @Observable
-class DeviceStat {
+final class DeviceStat: @unchecked Sendable {
+
+    @MainActor
     var gpuUsage = GPU.snapshot()
-    private var initialGPUSnapshot = GPU.snapshot()
+
+    private let initialGPUSnapshot = GPU.snapshot()
     private var timer: Timer?
 
     init() {
-        startTimer()
-    }
-
-    deinit {
-        stopTimer()
-    }
-
-    private func startTimer() {
-        timer?.invalidate()
         timer = Timer.scheduledTimer(withTimeInterval: 2.0, repeats: true) { [weak self] _ in
-            self?.updateStats()
+            self?.updateGPUUsages()
         }
     }
 
-    private func stopTimer() {
+    deinit {
         timer?.invalidate()
-        timer = nil
-    }
-
-    private func updateStats() {
-        updateGPUUsages()
     }
 
     private func updateGPUUsages() {