LeNet on MNIST + readme update (#12)

* LeNet on MNIST + readme update

* tanh + remove device toggle

* remove device entirely

Applications/MNISTTrainer/ContentView.swift

@@ -12,9 +12,6 @@ struct ContentView: View {
     // the training loop
     @State var trainer = Trainer()
 
-    // toggle for cpu/gpu training
-    @State var cpu = true
-
     var body: some View {
         VStack {
             Spacer()
@@ -30,13 +27,10 @@ struct ContentView: View {
 
                 Button("Train") {
                     Task {
-                        try! await trainer.run(device: cpu ? .cpu : .gpu)
+                        try! await trainer.run()
                     }
                 }
 
-                Toggle("CPU", isOn: $cpu)
-                    .frame(maxWidth: 150)
-
                 Spacer()
             }
             Spacer()
@@ -50,12 +44,10 @@ class Trainer {
 
     var messages = [String]()
 
-    func run(device: Device = .cpu) async throws {
+    func run() async throws {
         // Note: this is pretty close to the code in `mnist-tool`, just
         // wrapped in an Observable to make it easy to display in SwiftUI
 
-        Device.setDefault(device: device)
-
         // download & load the training data
         let url = URL(fileURLWithPath: NSTemporaryDirectory(), isDirectory: true)
         try await download(into: url)
@@ -67,9 +59,7 @@ class Trainer {
         let testLabels = data[.init(.test, .labels)]!
 
         // create the model with random weights
-        let model = MLP(
-            layers: 2, inputDimensions: trainImages.dim(-1), hiddenDimensions: 32,
-            outputDimensions: 10)
+        let model = LeNet()
         eval(model.parameters())
 
         // the training loop