# Code Examples

This page provides comprehensive code examples for the ruv-FANN Neural Network Framework, covering everything from basic usage to advanced optimizations.

## Table of Contents

1. [Basic Neural Network Examples](#basic-neural-network-examples)
2. [Advanced SIMD Optimizations](#advanced-simd-optimizations)
3. [Swarm Coordination Examples](#swarm-coordination-examples)
4. [WebAssembly Integration](#webassembly-integration)
5. [GPU Acceleration Examples](#gpu-acceleration-examples)
6. [Distributed Training Examples](#distributed-training-examples)

## Basic Neural Network Examples

### Creating a Simple Feed-Forward Network

```rust
use ruv_fann::{Network, ActivationFunction, TrainingData};

fn main() -> Result<(), Box<dyn std::error::Error>> {
    // Create a 3-layer network: 2 inputs, 3 hidden, 1 output
    let mut net = Network::new(&[2, 3, 1])?;
    
    // Configure activation functions
    net.set_activation_function_hidden(ActivationFunction::Sigmoid);
    net.set_activation_function_output(ActivationFunction::Linear);
    
    // Set learning parameters
    net.set_learning_rate(0.7);
    net.set_training_algorithm(TrainingAlgorithm::Rprop);
    
    // Create training data for XOR problem
    let training_data = TrainingData::new(
        vec![
            vec![0.0, 0.0], vec![0.0, 1.0],
            vec![1.0, 0.0], vec![1.0, 1.0]
        ],
        vec![
            vec![0.0], vec![1.0],
            vec![1.0], vec![0.0]
        ]
    )?;
    
    // Train the network
    net.train_on_data(&training_data, 500, 10, 0.001)?;
    
    // Test the network
    let output = net.run(&[1.0, 0.0])?;
    println!("XOR(1,0) = {:.3}", output[0]);
    
    Ok(())
}
```

### Convolutional Neural Network

```rust
use ruv_fann::{ConvNet, ConvLayer, PoolLayer, DenseLayer, ActivationFunction};

fn create_cnn_mnist() -> Result<ConvNet, Box<dyn std::error::Error>> {
    let mut cnn = ConvNet::new();
    
    // Input: 28x28x1 grayscale images
    cnn.add_layer(ConvLayer::new(
        32,          // 32 filters
        (3, 3),      // 3x3 kernel
        (1, 1),      // stride
        "same",      // padding
        ActivationFunction::ReLU
    )?);
    
    cnn.add_layer(PoolLayer::new(
        (2, 2),      // 2x2 pool size
        (2, 2),      // stride
        "max"        // max pooling
    )?);
    
    cnn.add_layer(ConvLayer::new(
        64,          // 64 filters
        (3, 3),      // 3x3 kernel
        (1, 1),      // stride
        "same",      // padding
        ActivationFunction::ReLU
    )?);
    
    cnn.add_layer(PoolLayer::new(
        (2, 2),      // 2x2 pool size
        (2, 2),      // stride
        "max"        // max pooling
    )?);
    
    // Flatten and add dense layers
    cnn.add_layer(DenseLayer::new(128, ActivationFunction::ReLU)?);
    cnn.add_layer(DenseLayer::new(10, ActivationFunction::Softmax)?); // 10 classes
    
    // Configure optimizer
    cnn.set_optimizer(Optimizer::Adam {
        learning_rate: 0.001,
        beta1: 0.9,
        beta2: 0.999,
        epsilon: 1e-8
    });
    
    Ok(cnn)
}
```

### Recurrent Neural Network (LSTM)

```rust
use ruv_fann::{LSTM, RNNCell, SequenceData};

fn create_lstm_time_series() -> Result<LSTM, Box<dyn std::error::Error>> {
    let mut lstm = LSTM::new();
    
    // LSTM layer with 50 hidden units
    lstm.add_layer(RNNCell::LSTM {
        hidden_size: 50,
        return_sequences: true,
        dropout: 0.2
    })?;
    
    // Another LSTM layer
    lstm.add_layer(RNNCell::LSTM {
        hidden_size: 50,
        return_sequences: false,
        dropout: 0.2
    })?);
    
    // Dense output layer
    lstm.add_layer(DenseLayer::new(1, ActivationFunction::Linear)?);
    
    // Configure for time series prediction
    lstm.set_sequence_length(10);  // Look back 10 time steps
    lstm.set_optimizer(Optimizer::RMSprop {
        learning_rate: 0.001,
        decay: 0.9
    });
    
    Ok(lstm)
}
```

## Advanced SIMD Optimizations

### SIMD Matrix Multiplication

```rust
use ruv_fann::simd::{SimdMatrix, simd_gemm};
use std::arch::x86_64::*;

#[cfg(target_arch = "x86_64")]
unsafe fn optimized_matrix_multiply(
    a: &SimdMatrix<f32>,
    b: &SimdMatrix<f32>,
    c: &mut SimdMatrix<f32>
) -> Result<(), Box<dyn std::error::Error>> {
    // Ensure matrices are properly aligned for SIMD
    assert!(a.is_aligned(32));
    assert!(b.is_aligned(32));
    assert!(c.is_aligned(32));
    
    let m = a.rows();
    let n = b.cols();
    let k = a.cols();
    
    // Use AVX2 for 8 float32s at once
    for i in (0..m).step_by(8) {
        for j in (0..n).step_by(8) {
            let mut acc = [_mm256_setzero_ps(); 8];
            
            for l in (0..k).step_by(8) {
                // Load 8x8 block from matrix A
                let a_block = [
                    _mm256_load_ps(a.ptr().add(i * k + l)),
                    _mm256_load_ps(a.ptr().add((i + 1) * k + l)),
                    _mm256_load_ps(a.ptr().add((i + 2) * k + l)),
                    _mm256_load_ps(a.ptr().add((i + 3) * k + l)),
                    _mm256_load_ps(a.ptr().add((i + 4) * k + l)),
                    _mm256_load_ps(a.ptr().add((i + 5) * k + l)),
                    _mm256_load_ps(a.ptr().add((i + 6) * k + l)),
                    _mm256_load_ps(a.ptr().add((i + 7) * k + l)),
                ];
                
                // Load 8x8 block from matrix B
                let b_block = [
                    _mm256_load_ps(b.ptr().add(l * n + j)),
                    _mm256_load_ps(b.ptr().add((l + 1) * n + j)),
                    _mm256_load_ps(b.ptr().add((l + 2) * n + j)),
                    _mm256_load_ps(b.ptr().add((l + 3) * n + j)),
                    _mm256_load_ps(b.ptr().add((l + 4) * n + j)),
                    _mm256_load_ps(b.ptr().add((l + 5) * n + j)),
                    _mm256_load_ps(b.ptr().add((l + 6) * n + j)),
                    _mm256_load_ps(b.ptr().add((l + 7) * n + j)),
                ];
                
                // Perform fused multiply-add
                for row in 0..8 {
                    for col in 0..8 {
                        acc[row] = _mm256_fmadd_ps(
                            _mm256_broadcast_ss(&a_block[row] as *const __m256 as *const f32),
                            b_block[col],
                            acc[row]
                        );
                    }
                }
            }
            
            // Store results
            for row in 0..8 {
                _mm256_store_ps(c.mut_ptr().add((i + row) * n + j), acc[row]);
            }
        }
    }
    
    Ok(())
}
```

### SIMD Activation Functions

```rust
use ruv_fann::simd::SimdVector;
use std::arch::x86_64::*;

#[cfg(target_arch = "x86_64")]
pub struct SimdActivations;

impl SimdActivations {
    #[target_feature(enable = "avx2,fma")]
    pub unsafe fn relu_avx2(input: &mut SimdVector<f32>) {
        let zero = _mm256_setzero_ps();
        let len = input.len();
        let ptr = input.as_mut_ptr();
        
        for i in (0..len).step_by(8) {
            let vals = _mm256_loadu_ps(ptr.add(i));
            let result = _mm256_max_ps(vals, zero);
            _mm256_storeu_ps(ptr.add(i), result);
        }
    }
    
    #[target_feature(enable = "avx2,fma")]
    pub unsafe fn tanh_avx2(input: &mut SimdVector<f32>) {
        let len = input.len();
        let ptr = input.as_mut_ptr();
        
        // Constants for tanh approximation
        let one = _mm256_set1_ps(1.0);
        let two = _mm256_set1_ps(2.0);
        let neg_two = _mm256_set1_ps(-2.0);
        
        for i in (0..len).step_by(8) {
            let x = _mm256_loadu_ps(ptr.add(i));
            
            // tanh(x) ≈ (exp(2x) - 1) / (exp(2x) + 1)
            let exp_2x = simd_exp(_mm256_mul_ps(two, x));
            let numerator = _mm256_sub_ps(exp_2x, one);
            let denominator = _mm256_add_ps(exp_2x, one);
            let result = _mm256_div_ps(numerator, denominator);
            
            _mm256_storeu_ps(ptr.add(i), result);
        }
    }
    
    #[target_feature(enable = "avx2,fma")]
    pub unsafe fn softmax_avx2(input: &mut SimdVector<f32>) {
        let len = input.len();
        let ptr = input.as_mut_ptr();
        
        // Find maximum for numerical stability
        let mut max_val = f32::NEG_INFINITY;
        for i in 0..len {
            max_val = max_val.max(*ptr.add(i));
        }
        let max_vec = _mm256_set1_ps(max_val);
        
        // Compute exp(x - max) and sum
        let mut sum = _mm256_setzero_ps();
        for i in (0..len).step_by(8) {
            let x = _mm256_loadu_ps(ptr.add(i));
            let shifted = _mm256_sub_ps(x, max_vec);
            let exp_x = simd_exp(shifted);
            _mm256_storeu_ps(ptr.add(i), exp_x);
            sum = _mm256_add_ps(sum, exp_x);
        }
        
        // Sum all elements in the vector
        let sum_scalar = horizontal_sum_avx2(sum);
        let sum_vec = _mm256_set1_ps(sum_scalar);
        
        // Divide by sum
        for i in (0..len).step_by(8) {
            let vals = _mm256_loadu_ps(ptr.add(i));
            let result = _mm256_div_ps(vals, sum_vec);
            _mm256_storeu_ps(ptr.add(i), result);
        }
    }
}
```

## Swarm Coordination Examples

### Distributed Training Coordinator

```rust
use ruv_fann::swarm::{SwarmCoordinator, SwarmNode, ConsensusProtocol};
use tokio::net::TcpListener;

#[tokio::main]
async fn distributed_training_example() -> Result<(), Box<dyn std::error::Error>> {
    // Initialize swarm coordinator
    let mut coordinator = SwarmCoordinator::new("coordinator-1".to_string());
    
    // Set up Byzantine fault tolerance
    coordinator.set_consensus_protocol(ConsensusProtocol::Byzantine {
        fault_tolerance: 1,  // Can handle 1 faulty node
        timeout_ms: 5000,
    });
    
    // Define training configuration
    let training_config = TrainingConfig {
        batch_size: 32,
        learning_rate: 0.001,
        epochs: 100,
        gradient_sync_frequency: 10,
    };
    
    // Start coordinator server
    let listener = TcpListener::bind("0.0.0.0:8080").await?;
    println!("Swarm coordinator listening on port 8080");
    
    // Spawn coordination task
    tokio::spawn(async move {
        coordinator.run_coordination_loop(listener, training_config).await
    });
    
    // Wait for nodes to connect
    tokio::time::sleep(tokio::time::Duration::from_secs(2)).await;
    
    // Start training across the swarm
    let training_handle = tokio::spawn(async move {
        coordinate_distributed_training().await
    });
    
    training_handle.await??;
    Ok(())
}

async fn coordinate_distributed_training() -> Result<(), Box<dyn std::error::Error>> {
    let coordinator = SwarmCoordinator::connect("127.0.0.1:8080").await?;
    
    // Initialize model parameters across all nodes
    coordinator.broadcast_model_parameters().await?;
    
    // Training loop
    for epoch in 0..100 {
        println!("Starting epoch {}", epoch);
        
        // Each node trains on its local data
        let local_gradients = coordinator.local_training_step().await?;
        
        // Aggregate gradients using Byzantine consensus
        let aggregated_gradients = coordinator.aggregate_gradients(
            local_gradients,
            ConsensusAlgorithm::ByzantineMedian
        ).await?;
        
        // Update model parameters
        coordinator.update_model_parameters(aggregated_gradients).await?;
        
        // Evaluate on validation set every 10 epochs
        if epoch % 10 == 0 {
            let validation_metrics = coordinator.evaluate_model().await?;
            println!("Epoch {}: Loss = {:.4}, Accuracy = {:.2}%", 
                    epoch, validation_metrics.loss, validation_metrics.accuracy * 100.0);
        }
    }
    
    Ok(())
}
```

### Hierarchical Swarm Architecture

```rust
use ruv_fann::swarm::{HierarchicalSwarm, SwarmLevel, NodeRole};

async fn hierarchical_swarm_example() -> Result<(), Box<dyn std::error::Error>> {
    // Create hierarchical swarm with 3 levels
    let mut swarm = HierarchicalSwarm::new(3);
    
    // Level 0: Master coordinator
    swarm.add_node(SwarmLevel::Master, SwarmNode::new(
        "master-1",
        NodeRole::Coordinator,
        "192.168.1.100:8080"
    )).await?;
    
    // Level 1: Regional coordinators
    for i in 0..3 {
        swarm.add_node(SwarmLevel::Regional(i), SwarmNode::new(
            &format!("regional-{}", i),
            NodeRole::RegionalCoordinator,
            &format!("192.168.{}.100:8080", i + 2)
        )).await?;
    }
    
    // Level 2: Worker nodes
    for region in 0..3 {
        for worker in 0..4 {
            swarm.add_node(SwarmLevel::Worker(region), SwarmNode::new(
                &format!("worker-{}-{}", region, worker),
                NodeRole::Worker,
                &format!("192.168.{}.{}:8080", region + 2, worker + 10)
            )).await?;
        }
    }
    
    // Configure communication patterns
    swarm.set_communication_topology(CommunicationTopology::Tree {
        branching_factor: 4,
        max_depth: 3,
    });
    
    // Start the swarm
    swarm.initialize().await?;
    
    // Begin hierarchical training
    swarm.start_hierarchical_training(HierarchicalConfig {
        aggregation_strategy: AggregationStrategy::WeightedAverage,
        synchronization_frequency: Duration::from_secs(30),
        fault_tolerance: FaultTolerance::Byzantine { max_faults: 1 },
    }).await?;
    
    Ok(())
}
```

### Gossip Protocol Implementation

```rust
use ruv_fann::swarm::{GossipProtocol, GossipMessage, PeerInfo};
use rand::seq::SliceRandom;

pub struct ModelGossip {
    node_id: String,
    peers: Vec<PeerInfo>,
    model_updates: HashMap<String, ModelUpdate>,
    gossip_frequency: Duration,
}

impl ModelGossip {
    pub fn new(node_id: String, gossip_frequency: Duration) -> Self {
        Self {
            node_id,
            peers: Vec::new(),
            model_updates: HashMap::new(),
            gossip_frequency,
        }
    }
    
    pub async fn start_gossip_loop(&mut self) -> Result<(), Box<dyn std::error::Error>> {
        let mut interval = tokio::time::interval(self.gossip_frequency);
        
        loop {
            interval.tick().await;
            
            // Select random subset of peers for gossip
            let mut rng = rand::thread_rng();
            let gossip_peers: Vec<_> = self.peers
                .choose_multiple(&mut rng, 3)
                .cloned()
                .collect();
            
            // Send model updates to selected peers
            for peer in gossip_peers {
                let message = GossipMessage::ModelUpdate {
                    sender: self.node_id.clone(),
                    timestamp: SystemTime::now(),
                    model_delta: self.get_latest_model_delta(),
                    version: self.get_model_version(),
                };
                
                if let Err(e) = self.send_gossip_message(&peer, message).await {
                    eprintln!("Failed to gossip with peer {}: {}", peer.id, e);
                    // Mark peer as potentially faulty
                    self.mark_peer_suspicious(&peer.id);
                }
            }
            
            // Clean up old model updates
            self.cleanup_old_updates();
        }
    }
    
    pub async fn handle_gossip_message(&mut self, message: GossipMessage) -> Result<(), Box<dyn std::error::Error>> {
        match message {
            GossipMessage::ModelUpdate { sender, timestamp, model_delta, version } => {
                // Validate message authenticity and freshness
                if self.validate_model_update(&sender, &model_delta, version, timestamp) {
                    // Apply model update with conflict resolution
                    self.merge_model_update(sender, model_delta, version).await?;
                    
                    // Propagate to other peers with some probability
                    if rand::random::<f32>() < 0.7 {
                        self.propagate_update(message).await?;
                    }
                }
            },
            GossipMessage::PeerDiscovery { sender, peers } => {
                // Update peer list
                for peer in peers {
                    if peer.id != self.node_id && !self.peers.contains(&peer) {
                        self.peers.push(peer);
                    }
                }
            },
            GossipMessage::Heartbeat { sender, timestamp } => {
                // Update peer liveness
                self.update_peer_liveness(&sender, timestamp);
            }
        }
        
        Ok(())
    }
    
    async fn merge_model_update(
        &mut self, 
        sender: String, 
        model_delta: ModelDelta, 
        version: u64
    ) -> Result<(), Box<dyn std::error::Error>> {
        // Implement CRDT-based conflict resolution
        let current_update = self.model_updates.entry(sender.clone()).or_insert_with(|| {
            ModelUpdate::new(version, model_delta.clone())
        });
        
        if version > current_update.version {
            // Newer update, apply directly
            current_update.apply_delta(model_delta)?;
            current_update.version = version;
        } else if version == current_update.version {
            // Concurrent update, merge using CRDT rules
            current_update.merge_concurrent_delta(model_delta)?;
        }
        // Ignore older updates
        
        Ok(())
    }
}
```

## WebAssembly Integration

### WASM Neural Network Module

```rust
use wasm_bindgen::prelude::*;
use ruv_fann::{Network, ActivationFunction};

#[wasm_bindgen]
pub struct WasmNeuralNetwork {
    network: Network,
}

#[wasm_bindgen]
impl WasmNeuralNetwork {
    #[wasm_bindgen(constructor)]
    pub fn new(layers: &[u32]) -> Result<WasmNeuralNetwork, JsValue> {
        console_error_panic_hook::set_once();
        
        let network = Network::new(layers)
            .map_err(|e| JsValue::from_str(&e.to_string()))?;
        
        Ok(WasmNeuralNetwork { network })
    }
    
    #[wasm_bindgen]
    pub fn set_activation_function(&mut self, function: &str) -> Result<(), JsValue> {
        let activation = match function {
            "sigmoid" => ActivationFunction::Sigmoid,
            "tanh" => ActivationFunction::Tanh,
            "relu" => ActivationFunction::ReLU,
            "leaky_relu" => ActivationFunction::LeakyReLU(0.01),
            "softmax" => ActivationFunction::Softmax,
            _ => return Err(JsValue::from_str("Unknown activation function"))
        };
        
        self.network.set_activation_function_hidden(activation);
        Ok(())
    }
    
    #[wasm_bindgen]
    pub fn train_batch(&mut self, inputs: &[f32], targets: &[f32], batch_size: usize) -> Result<f32, JsValue> {
        let input_size = self.network.get_num_input();
        let output_size = self.network.get_num_output();
        
        if inputs.len() % (batch_size * input_size) != 0 {
            return Err(JsValue::from_str("Invalid input batch size"));
        }
        
        if targets.len() % (batch_size * output_size) != 0 {
            return Err(JsValue::from_str("Invalid target batch size"));
        }
        
        let mut total_error = 0.0;
        
        for batch in 0..batch_size {
            let input_start = batch * input_size;
            let input_end = input_start + input_size;
            let target_start = batch * output_size;
            let target_end = target_start + output_size;
            
            let batch_input = &inputs[input_start..input_end];
            let batch_target = &targets[target_start..target_end];
            
            let error = self.network.train(batch_input, batch_target)
                .map_err(|e| JsValue::from_str(&e.to_string()))?;
            
            total_error += error;
        }
        
        Ok(total_error / batch_size as f32)
    }
    
    #[wasm_bindgen]
    pub fn predict(&mut self, inputs: &[f32]) -> Result<Vec<f32>, JsValue> {
        let outputs = self.network.run(inputs)
            .map_err(|e| JsValue::from_str(&e.to_string()))?;
        Ok(outputs)
    }
    
    #[wasm_bindgen]
    pub fn get_weights(&self) -> Vec<f32> {
        self.network.get_weights()
    }
    
    #[wasm_bindgen]
    pub fn set_weights(&mut self, weights: &[f32]) -> Result<(), JsValue> {
        self.network.set_weights(weights)
            .map_err(|e| JsValue::from_str(&e.to_string()))
    }
    
    #[wasm_bindgen]
    pub fn save_to_bytes(&self) -> Result<Vec<u8>, JsValue> {
        self.network.serialize()
            .map_err(|e| JsValue::from_str(&e.to_string()))
    }
    
    #[wasm_bindgen]
    pub fn load_from_bytes(data: &[u8]) -> Result<WasmNeuralNetwork, JsValue> {
        let network = Network::deserialize(data)
            .map_err(|e| JsValue::from_str(&e.to_string()))?;
        Ok(WasmNeuralNetwork { network })
    }
}
```

### JavaScript Integration

```javascript
// neural-network-worker.js
import init, { WasmNeuralNetwork } from './ruv_fann_wasm.js';

class NeuralNetworkWorker {
    constructor() {
        this.network = null;
        this.isInitialized = false;
    }
    
    async initialize() {
        await init();
        this.isInitialized = true;
    }
    
    createNetwork(layers) {
        if (!this.isInitialized) {
            throw new Error('WASM module not initialized');
        }
        
        this.network = new WasmNeuralNetwork(new Uint32Array(layers));
        return { status: 'success', message: 'Network created' };
    }
    
    trainBatch(inputs, targets) {
        if (!this.network) {
            throw new Error('Network not created');
        }
        
        const inputArray = new Float32Array(inputs);
        const targetArray = new Float32Array(targets);
        const batchSize = inputs.length / this.network.get_num_input();
        
        try {
            const error = this.network.train_batch(inputArray, targetArray, batchSize);
            return { status: 'success', error: error };
        } catch (e) {
            return { status: 'error', message: e.toString() };
        }
    }
    
    predict(inputs) {
        if (!this.network) {
            throw new Error('Network not created');
        }
        
        try {
            const outputs = this.network.predict(new Float32Array(inputs));
            return { status: 'success', outputs: Array.from(outputs) };
        } catch (e) {
            return { status: 'error', message: e.toString() };
        }
    }
    
    saveModel() {
        if (!this.network) {
            throw new Error('Network not created');
        }
        
        try {
            const bytes = this.network.save_to_bytes();
            return { status: 'success', data: Array.from(bytes) };
        } catch (e) {
            return { status: 'error', message: e.toString() };
        }
    }
    
    loadModel(data) {
        try {
            this.network = WasmNeuralNetwork.load_from_bytes(new Uint8Array(data));
            return { status: 'success', message: 'Model loaded' };
        } catch (e) {
            return { status: 'error', message: e.toString() };
        }
    }
}

// Worker message handler
self.onmessage = async function(e) {
    const { id, method, params } = e.data;
    
    if (!self.neuralWorker) {
        self.neuralWorker = new NeuralNetworkWorker();
        await self.neuralWorker.initialize();
    }
    
    try {
        let result;
        switch (method) {
            case 'createNetwork':
                result = self.neuralWorker.createNetwork(params.layers);
                break;
            case 'trainBatch':
                result = self.neuralWorker.trainBatch(params.inputs, params.targets);
                break;
            case 'predict':
                result = self.neuralWorker.predict(params.inputs);
                break;
            case 'saveModel':
                result = self.neuralWorker.saveModel();
                break;
            case 'loadModel':
                result = self.neuralWorker.loadModel(params.data);
                break;
            default:
                throw new Error(`Unknown method: ${method}`);
        }
        
        self.postMessage({ id, result });
    } catch (error) {
        self.postMessage({ 
            id, 
            error: { status: 'error', message: error.message } 
        });
    }
};
```

### Browser Integration Example

```html
<!DOCTYPE html>
<html>
<head>
    <title>ruv-FANN Web Demo</title>
</head>
<body>
    <div id="app">
        <h1>Neural Network Training Demo</h1>
        <div>
            <label>Network Architecture:</label>
            <input type="text" id="layers" value="2,4,1" placeholder="e.g., 2,4,1">
        </div>
        <div>
            <label>Learning Rate:</label>
            <input type="number" id="learningRate" value="0.1" step="0.01">
        </div>
        <button onclick="createNetwork()">Create Network</button>
        <button onclick="trainNetwork()">Train XOR</button>
        <button onclick="testNetwork()">Test</button>
        <div id="output"></div>
        <canvas id="visualization" width="400" height="300"></canvas>
    </div>

    <script type="module">
        import init, { WasmNeuralNetwork } from './ruv_fann_wasm.js';
        
        let network = null;
        
        async function initializeWasm() {
            await init();
            console.log('WASM initialized');
        }
        
        window.createNetwork = function() {
            const layersInput = document.getElementById('layers').value;
            const layers = layersInput.split(',').map(x => parseInt(x.trim()));
            
            try {
                network = new WasmNeuralNetwork(new Uint32Array(layers));
                network.set_activation_function('sigmoid');
                document.getElementById('output').innerHTML = 'Network created successfully!';
            } catch (e) {
                document.getElementById('output').innerHTML = `Error: ${e}`;
            }
        };
        
        window.trainNetwork = async function() {
            if (!network) {
                alert('Please create a network first');
                return;
            }
            
            // XOR training data
            const inputs = [0, 0,  0, 1,  1, 0,  1, 1];
            const targets = [0,  1,  1,  0];
            
            const output = document.getElementById('output');
            output.innerHTML = 'Training started...<br>';
            
            for (let epoch = 0; epoch < 1000; epoch++) {
                const error = network.train_batch(
                    new Float32Array(inputs), 
                    new Float32Array(targets), 
                    4
                );
                
                if (epoch % 100 === 0) {
                    output.innerHTML += `Epoch ${epoch}: Error = ${error.toFixed(6)}<br>`;
                }
                
                // Allow UI to update
                if (epoch % 50 === 0) {
                    await new Promise(resolve => setTimeout(resolve, 1));
                }
            }
            
            output.innerHTML += 'Training completed!<br>';
        };
        
        window.testNetwork = function() {
            if (!network) {
                alert('Please create and train a network first');
                return;
            }
            
            const testCases = [
                [0, 0], [0, 1], [1, 0], [1, 1]
            ];
            const expected = [0, 1, 1, 0];
            
            let results = 'Test Results:<br>';
            testCases.forEach((input, i) => {
                const output = network.predict(new Float32Array(input));
                results += `XOR(${input[0]}, ${input[1]}) = ${output[0].toFixed(3)} (expected: ${expected[i]})<br>`;
            });
            
            document.getElementById('output').innerHTML = results;
        };
        
        // Initialize when page loads
        initializeWasm();
    </script>
</body>
</html>
```

## GPU Acceleration Examples

### CUDA Neural Network Training

```rust
use ruv_fann::gpu::{CudaNetwork, CudaMemory, CudaKernel};
use cudarc::driver::{CudaDevice, DeviceRepr};

pub struct GpuNeuralNetwork {
    device: CudaDevice,
    weights: CudaMemory<f32>,
    biases: CudaMemory<f32>,
    activations: CudaMemory<f32>,
    gradients: CudaMemory<f32>,
    layer_sizes: Vec<usize>,
}

impl GpuNeuralNetwork {
    pub fn new(layer_sizes: Vec<usize>) -> Result<Self, Box<dyn std::error::Error>> {
        let device = CudaDevice::new(0)?; // Use GPU 0
        
        // Calculate total weights and biases needed
        let total_weights: usize = layer_sizes.windows(2)
            .map(|pair| pair[0] * pair[1])
            .sum();
        let total_biases: usize = layer_sizes[1..].iter().sum();
        let max_layer_size = *layer_sizes.iter().max().unwrap();
        
        // Allocate GPU memory
        let weights = device.alloc_zeros::<f32>(total_weights)?;
        let biases = device.alloc_zeros::<f32>(total_biases)?;
        let activations = device.alloc_zeros::<f32>(max_layer_size)?;
        let gradients = device.alloc_zeros::<f32>(total_weights)?;
        
        // Initialize weights with Xavier initialization
        let mut host_weights = vec![0.0f32; total_weights];
        let mut weight_idx = 0;
        for pair in layer_sizes.windows(2) {
            let fan_in = pair[0];
            let fan_out = pair[1];
            let bound = (6.0 / (fan_in + fan_out) as f32).sqrt();
            
            for _ in 0..(fan_in * fan_out) {
                host_weights[weight_idx] = (rand::random::<f32>() - 0.5) * 2.0 * bound;
                weight_idx += 1;
            }
        }
        device.htod_copy(host_weights, &weights)?;
        
        Ok(Self {
            device,
            weights,
            biases,
            activations,
            gradients,
            layer_sizes,
        })
    }
    
    pub fn forward_pass(&mut self, input: &[f32]) -> Result<Vec<f32>, Box<dyn std::error::Error>> {
        // Copy input to GPU
        let mut current_activations = self.device.alloc_zeros::<f32>(input.len())?;
        self.device.htod_copy(input.to_vec(), &current_activations)?;
        
        let mut weight_offset = 0;
        let mut bias_offset = 0;
        
        for layer_idx in 1..self.layer_sizes.len() {
            let input_size = self.layer_sizes[layer_idx - 1];
            let output_size = self.layer_sizes[layer_idx];
            
            // Allocate memory for next layer
            let next_activations = self.device.alloc_zeros::<f32>(output_size)?;
            
            // Launch matrix multiplication kernel
            let grid_size = (output_size + 255) / 256;
            let block_size = 256;
            
            unsafe {
                matrix_vector_multiply_kernel::launch(
                    &self.device,
                    (grid_size, 1, 1),
                    (block_size, 1, 1),
                    &[
                        &self.weights.slice(weight_offset..weight_offset + input_size * output_size),
                        &current_activations,
                        &self.biases.slice(bias_offset..bias_offset + output_size),
                        &next_activations,
                        &input_size,
                        &output_size,
                    ],
                )?;
            }
            
            // Apply activation function
            let activation_grid = (output_size + 255) / 256;
            unsafe {
                if layer_idx == self.layer_sizes.len() - 1 {
                    // Output layer - linear activation
                    // No additional activation needed
                } else {
                    // Hidden layer - ReLU activation
                    relu_activation_kernel::launch(
                        &self.device,
                        (activation_grid, 1, 1),
                        (block_size, 1, 1),
                        &[&next_activations, &output_size],
                    )?;
                }
            }
            
            current_activations = next_activations;
            weight_offset += input_size * output_size;
            bias_offset += output_size;
        }
        
        // Copy result back to host
        let output_size = self.layer_sizes.last().unwrap();
        let mut output = vec![0.0f32; *output_size];
        self.device.dtoh_sync_copy(&current_activations, &mut output)?;
        
        Ok(output)
    }
    
    pub fn backward_pass(&mut self, target: &[f32]) -> Result<f32, Box<dyn std::error::Error>> {
        // Compute output layer error
        let output_size = *self.layer_sizes.last().unwrap();
        let mut output_errors = self.device.alloc_zeros::<f32>(output_size)?;
        
        // Launch error computation kernel
        let grid_size = (output_size + 255) / 256;
        unsafe {
            compute_output_error_kernel::launch(
                &self.device,
                (grid_size, 1, 1),
                (256, 1, 1),
                &[
                    &self.activations,
                    &self.device.htod_copy(target.to_vec(), &output_errors)?,
                    &output_errors,
                    &output_size,
                ],
            )?;
        }
        
        // Backpropagate errors through network
        let mut current_errors = output_errors;
        let mut weight_offset = 0;
        
        // Calculate total weights up to current layer
        for pair in self.layer_sizes.windows(2).rev().skip(1) {
            weight_offset += pair[0] * pair[1];
        }
        
        for layer_idx in (1..self.layer_sizes.len()).rev() {
            let input_size = self.layer_sizes[layer_idx - 1];
            let output_size = self.layer_sizes[layer_idx];
            
            if layer_idx > 1 {
                // Propagate errors to previous layer
                let prev_errors = self.device.alloc_zeros::<f32>(input_size)?;
                
                let grid_size = (input_size + 255) / 256;
                unsafe {
                    backprop_error_kernel::launch(
                        &self.device,
                        (grid_size, 1, 1),
                        (256, 1, 1),
                        &[
                            &self.weights.slice(weight_offset..weight_offset + input_size * output_size),
                            &current_errors,
                            &prev_errors,
                            &input_size,
                            &output_size,
                        ],
                    )?;
                }
                
                current_errors = prev_errors;
            }
            
            // Update weights and biases
            let grid_size = (input_size * output_size + 255) / 256;
            unsafe {
                update_weights_kernel::launch(
                    &self.device,
                    (grid_size, 1, 1),
                    (256, 1, 1),
                    &[
                        &self.weights.slice(weight_offset..weight_offset + input_size * output_size),
                        &self.gradients.slice(weight_offset..weight_offset + input_size * output_size),
                        &current_errors,
                        &self.activations, // Previous layer activations
                        &0.01f32, // Learning rate
                        &input_size,
                        &output_size,
                    ],
                )?;
            }
            
            weight_offset -= if layer_idx > 1 { 
                self.layer_sizes[layer_idx - 2] * self.layer_sizes[layer_idx - 1] 
            } else { 
                0 
            };
        }
        
        // Calculate and return loss
        let mut loss = vec![0.0f32; 1];
        unsafe {
            compute_loss_kernel::launch(
                &self.device,
                (1, 1, 1),
                (1, 1, 1),
                &[
                    &self.activations,
                    &self.device.htod_copy(target.to_vec(), &output_errors)?,
                    &self.device.alloc_zeros::<f32>(1)?,
                    &output_size,
                ],
            )?;
        }
        
        Ok(loss[0])
    }
}

// CUDA kernels (would be compiled separately)
mod cuda_kernels {
    use cudarc::nvrtc::compile_ptx;
    
    pub const MATRIX_VECTOR_MULTIPLY_KERNEL: &str = r#"
    extern "C" __global__ void matrix_vector_multiply_kernel(
        const float* weights,
        const float* input,
        const float* biases,
        float* output,
        int input_size,
        int output_size
    ) {
        int idx = blockIdx.x * blockDim.x + threadIdx.x;
        
        if (idx < output_size) {
            float sum = biases[idx];
            for (int i = 0; i < input_size; i++) {
                sum += weights[idx * input_size + i] * input[i];
            }
            output[idx] = sum;
        }
    }
    "#;
    
    pub const RELU_ACTIVATION_KERNEL: &str = r#"
    extern "C" __global__ void relu_activation_kernel(
        float* values,
        int size
    ) {
        int idx = blockIdx.x * blockDim.x + threadIdx.x;
        
        if (idx < size) {
            values[idx] = fmaxf(0.0f, values[idx]);
        }
    }
    "#;
}
```

### Multi-GPU Training

```rust
use ruv_fann::gpu::{MultiGpuTrainer, DataParallelism, ModelParallelism};

pub struct MultiGpuNeuralNetwork {
    devices: Vec<CudaDevice>,
    models: Vec<GpuNeuralNetwork>,
    parallelism_strategy: ParallelismStrategy,
}

impl MultiGpuNeuralNetwork {
    pub fn new(
        layer_sizes: Vec<usize>,
        num_gpus: usize,
        strategy: ParallelismStrategy
    ) -> Result<Self, Box<dyn std::error::Error>> {
        let mut devices = Vec::new();
        let mut models = Vec::new();
        
        for gpu_id in 0..num_gpus {
            let device = CudaDevice::new(gpu_id)?;
            devices.push(device);
            
            match strategy {
                ParallelismStrategy::DataParallel => {
                    // Each GPU gets a complete copy of the model
                    models.push(GpuNeuralNetwork::new(layer_sizes.clone())?);
                },
                ParallelismStrategy::ModelParallel => {
                    // Split model across GPUs
                    let layers_per_gpu = layer_sizes.len() / num_gpus;
                    let start_layer = gpu_id * layers_per_gpu;
                    let end_layer = if gpu_id == num_gpus - 1 {
                        layer_sizes.len()
                    } else {
                        (gpu_id + 1) * layers_per_gpu
                    };
                    
                    let gpu_layers = layer_sizes[start_layer..end_layer].to_vec();
                    models.push(GpuNeuralNetwork::new(gpu_layers)?);
                }
            }
        }
        
        Ok(Self {
            devices,
            models,
            parallelism_strategy: strategy,
        })
    }
    
    pub async fn train_batch_parallel(
        &mut self,
        inputs: Vec<Vec<f32>>,
        targets: Vec<Vec<f32>>
    ) -> Result<f32, Box<dyn std::error::Error>> {
        match self.parallelism_strategy {
            ParallelismStrategy::DataParallel => {
                self.data_parallel_training(inputs, targets).await
            },
            ParallelismStrategy::ModelParallel => {
                self.model_parallel_training(inputs, targets).await
            }
        }
    }
    
    async fn data_parallel_training(
        &mut self,
        inputs: Vec<Vec<f32>>,
        targets: Vec<Vec<f32>>
    ) -> Result<f32, Box<dyn std::error::Error>> {
        let batch_size = inputs.len();
        let samples_per_gpu = batch_size / self.models.len();
        
        // Split batch across GPUs
        let mut tasks = Vec::new();
        for (gpu_id, model) in self.models.iter_mut().enumerate() {
            let start_idx = gpu_id * samples_per_gpu;
            let end_idx = if gpu_id == self.models.len() - 1 {
                batch_size
            } else {
                (gpu_id + 1) * samples_per_gpu
            };
            
            let gpu_inputs = inputs[start_idx..end_idx].to_vec();
            let gpu_targets = targets[start_idx..end_idx].to_vec();
            
            // Train on this GPU's portion of the batch
            tasks.push(tokio::spawn(async move {
                let mut total_loss = 0.0;
                for (input, target) in gpu_inputs.iter().zip(gpu_targets.iter()) {
                    model.forward_pass(input)?;
                    let loss = model.backward_pass(target)?;
                    total_loss += loss;
                }
                Ok::<f32, Box<dyn std::error::Error>>(total_loss / gpu_inputs.len() as f32)
            }));
        }
        
        // Wait for all GPUs to complete
        let mut total_loss = 0.0;
        for task in tasks {
            let gpu_loss = task.await??;
            total_loss += gpu_loss;
        }
        
        // Average gradients across GPUs using NCCL
        self.all_reduce_gradients().await?;
        
        Ok(total_loss / self.models.len() as f32)
    }
    
    async fn all_reduce_gradients(&mut self) -> Result<(), Box<dyn std::error::Error>> {
        // Implement NCCL AllReduce for gradient synchronization
        // This is a simplified version - real implementation would use NCCL
        
        let num_gpus = self.models.len();
        
        // Collect gradients from all GPUs
        let mut all_gradients = Vec::new();
        for model in &self.models {
            let gradients = model.get_gradients()?;
            all_gradients.push(gradients);
        }
        
        // Average gradients
        let gradient_size = all_gradients[0].len();
        let mut averaged_gradients = vec![0.0f32; gradient_size];
        
        for i in 0..gradient_size {
            let mut sum = 0.0;
            for gpu_gradients in &all_gradients {
                sum += gpu_gradients[i];
            }
            averaged_gradients[i] = sum / num_gpus as f32;
        }
        
        // Broadcast averaged gradients back to all GPUs
        for model in &mut self.models {
            model.set_gradients(&averaged_gradients)?;
        }
        
        Ok(())
    }
}

#[derive(Clone)]
pub enum ParallelismStrategy {
    DataParallel,
    ModelParallel,
}
```

## Distributed Training Examples

### Parameter Server Architecture

```rust
use ruv_fann::distributed::{ParameterServer, Worker, GradientUpdate};
use tokio::net::{TcpListener, TcpStream};
use serde::{Serialize, Deserialize};

#[derive(Serialize, Deserialize)]
pub struct ParameterUpdate {
    pub layer_id: usize,
    pub gradients: Vec<f32>,
    pub worker_id: String,
    pub version: u64,
}

pub struct DistributedParameterServer {
    parameters: HashMap<usize, Vec<f32>>,
    parameter_versions: HashMap<usize, u64>,
    workers: HashMap<String, WorkerInfo>,
    learning_rate: f32,
    momentum: f32,
    momentum_buffers: HashMap<usize, Vec<f32>>,
}

impl DistributedParameterServer {
    pub fn new(learning_rate: f32, momentum: f32) -> Self {
        Self {
            parameters: HashMap::new(),
            parameter_versions: HashMap::new(),
            workers: HashMap::new(),
            learning_rate,
            momentum,
            momentum_buffers: HashMap::new(),
        }
    }
    
    pub async fn start_server(&mut self, addr: &str) -> Result<(), Box<dyn std::error::Error>> {
        let listener = TcpListener::bind(addr).await?;
        println!("Parameter server listening on {}", addr);
        
        loop {
            let (stream, addr) = listener.accept().await?;
            println!("New connection from {}", addr);
            
            let server_handle = Arc::new(Mutex::new(self));
            tokio::spawn(async move {
                if let Err(e) = handle_worker_connection(stream, server_handle).await {
                    eprintln!("Error handling worker connection: {}", e);
                }
            });
        }
    }
    
    pub fn push_gradients(&mut self, update: ParameterUpdate) -> Result<(), Box<dyn std::error::Error>> {
        let layer_id = update.layer_id;
        let gradients = update.gradients;
        
        // Get current parameters and version
        let current_params = self.parameters.entry(layer_id).or_insert_with(|| {
            vec![0.0; gradients.len()]
        });
        let current_version = self.parameter_versions.entry(layer_id).or_insert(0);
        
        // Check for stale gradients
        if update.version < *current_version {
            return Err("Stale gradient update".into());
        }
        
        // Initialize momentum buffer if needed
        let momentum_buffer = self.momentum_buffers.entry(layer_id).or_insert_with(|| {
            vec![0.0; gradients.len()]
        });
        
        // Apply momentum and update parameters
        for i in 0..current_params.len() {
            // Update momentum buffer
            momentum_buffer[i] = self.momentum * momentum_buffer[i] + gradients[i];
            
            // Update parameters
            current_params[i] -= self.learning_rate * momentum_buffer[i];
        }
        
        // Increment version
        *current_version += 1;
        
        // Update worker statistics
        if let Some(worker_info) = self.workers.get_mut(&update.worker_id) {
            worker_info.last_update = SystemTime::now();
            worker_info.updates_sent += 1;
        }
        
        Ok(())
    }
    
    pub fn pull_parameters(&self, layer_id: usize) -> Option<(Vec<f32>, u64)> {
        if let (Some(params), Some(version)) = (
            self.parameters.get(&layer_id),
            self.parameter_versions.get(&layer_id)
        ) {
            Some((params.clone(), *version))
        } else {
            None
        }
    }
    
    pub fn register_worker(&mut self, worker_id: String, capabilities: WorkerCapabilities) {
        let worker_info = WorkerInfo {
            id: worker_id.clone(),
            capabilities,
            last_update: SystemTime::now(),
            updates_sent: 0,
            is_active: true,
        };
        
        self.workers.insert(worker_id, worker_info);
    }
}

#[derive(Clone)]
struct WorkerInfo {
    id: String,
    capabilities: WorkerCapabilities,
    last_update: SystemTime,
    updates_sent: u64,
    is_active: bool,
}

#[derive(Clone, Serialize, Deserialize)]
struct WorkerCapabilities {
    gpu_count: usize,
    memory_gb: f32,
    compute_capability: String,
}

pub struct DistributedWorker {
    worker_id: String,
    server_addr: String,
    local_model: GpuNeuralNetwork,
    parameter_cache: HashMap<usize, (Vec<f32>, u64)>,
    sync_frequency: usize,
    current_iteration: usize,
}

impl DistributedWorker {
    pub fn new(
        worker_id: String,
        server_addr: String,
        model_config: Vec<usize>
    ) -> Result<Self, Box<dyn std::error::Error>> {
        let local_model = GpuNeuralNetwork::new(model_config)?;
        
        Ok(Self {
            worker_id,
            server_addr,
            local_model,
            parameter_cache: HashMap::new(),
            sync_frequency: 10, // Sync every 10 iterations
            current_iteration: 0,
        })
    }
    
    pub async fn train_distributed(
        &mut self,
        training_data: Vec<(Vec<f32>, Vec<f32>)>
    ) -> Result<(), Box<dyn std::error::Error>> {
        // Connect to parameter server
        let mut stream = TcpStream::connect(&self.server_addr).await?;
        
        // Register with server
        self.register_with_server(&mut stream).await?;
        
        // Pull initial parameters
        self.pull_all_parameters(&mut stream).await?;
        
        // Training loop
        for (input, target) in training_data {
            // Forward pass
            let _output = self.local_model.forward_pass(&input)?;
            
            // Backward pass
            let _loss = self.local_model.backward_pass(&target)?;
            
            self.current_iteration += 1;
            
            // Sync with parameter server periodically
            if self.current_iteration % self.sync_frequency == 0 {
                self.sync_with_server(&mut stream).await?;
            }
        }
        
        Ok(())
    }
    
    async fn sync_with_server(&mut self, stream: &mut TcpStream) -> Result<(), Box<dyn std::error::Error>> {
        // Push gradients to server
        let gradients = self.local_model.get_gradients()?;
        
        // Split gradients by layer and send updates
        let mut gradient_offset = 0;
        for (layer_id, layer_size) in self.local_model.get_layer_sizes().windows(2).enumerate() {
            let layer_gradient_size = layer_size[0] * layer_size[1];
            let layer_gradients = gradients[gradient_offset..gradient_offset + layer_gradient_size].to_vec();
            
            let update = ParameterUpdate {
                layer_id,
                gradients: layer_gradients,
                worker_id: self.worker_id.clone(),
                version: self.get_parameter_version(layer_id),
            };
            
            self.send_gradient_update(stream, update).await?;
            gradient_offset += layer_gradient_size;
        }
        
        // Pull updated parameters
        self.pull_all_parameters(stream).await?;
        
        Ok(())
    }
    
    async fn pull_all_parameters(&mut self, stream: &mut TcpStream) -> Result<(), Box<dyn std::error::Error>> {
        let layer_count = self.local_model.get_layer_count();
        
        for layer_id in 0..layer_count {
            if let Some((params, version)) = self.pull_layer_parameters(stream, layer_id).await? {
                // Update local model with new parameters
                self.local_model.set_layer_parameters(layer_id, &params)?;
                
                // Update cache
                self.parameter_cache.insert(layer_id, (params, version));
            }
        }
        
        Ok(())
    }
    
    fn get_parameter_version(&self, layer_id: usize) -> u64 {
        self.parameter_cache.get(&layer_id)
            .map(|(_, version)| *version)
            .unwrap_or(0)
    }
}
```

### Federated Learning Implementation

```rust
use ruv_fann::federated::{FederatedServer, FederatedClient, AggregationStrategy};
use differential_privacy::{DifferentialPrivacy, NoiseDistribution};

pub struct FederatedLearningServer {
    global_model: Network,
    client_models: HashMap<String, ClientModel>,
    aggregation_strategy: AggregationStrategy,
    privacy_budget: f64,
    noise_mechanism: NoiseDistribution,
    round_number: u32,
    min_clients_per_round: usize,
}

impl FederatedLearningServer {
    pub fn new(
        model_config: Vec<usize>,
        aggregation_strategy: AggregationStrategy,
        privacy_budget: f64
    ) -> Result<Self, Box<dyn std::error::Error>> {
        let global_model = Network::new(&model_config)?;
        
        Ok(Self {
            global_model,
            client_models: HashMap::new(),
            aggregation_strategy,
            privacy_budget,
            noise_mechanism: NoiseDistribution::Gaussian { sigma: 0.1 },
            round_number: 0,
            min_clients_per_round: 5,
        })
    }
    
    pub async fn run_federated_round(&mut self) -> Result<(), Box<dyn std::error::Error>> {
        println!("Starting federated round {}", self.round_number);
        
        // Select clients for this round
        let selected_clients = self.select_clients_for_round().await?;
        println!("Selected {} clients for training", selected_clients.len());
        
        if selected_clients.len() < self.min_clients_per_round {
            return Err("Not enough clients available for training".into());
        }
        
        // Send global model to selected clients
        let global_weights = self.global_model.get_weights();
        for client_id in &selected_clients {
            self.send_model_to_client(client_id, &global_weights).await?;
        }
        
        // Wait for client updates
        let client_updates = self.collect_client_updates(selected_clients).await?;
        
        // Aggregate client models
        let aggregated_weights = self.aggregate_client_models(client_updates)?;
        
        // Apply differential privacy
        let private_weights = self.apply_differential_privacy(aggregated_weights)?;
        
        // Update global model
        self.global_model.set_weights(&private_weights)?;
        
        self.round_number += 1;
        println!("Completed federated round {}", self.round_number - 1);
        
        Ok(())
    }
    
    async fn select_clients_for_round(&self) -> Result<Vec<String>, Box<dyn std::error::Error>> {
        // Select a random subset of available clients
        let available_clients: Vec<String> = self.client_models.keys()
            .filter(|client_id| self.is_client_available(client_id))
            .cloned()
            .collect();
        
        let num_clients_to_select = std::cmp::min(
            available_clients.len(),
            (available_clients.len() as f32 * 0.3).ceil() as usize // Select 30% of clients
        );
        
        let mut rng = rand::thread_rng();
        let selected_clients = available_clients
            .choose_multiple(&mut rng, num_clients_to_select)
            .cloned()
            .collect();
        
        Ok(selected_clients)
    }
    
    async fn collect_client_updates(
        &mut self,
        selected_clients: Vec<String>
    ) -> Result<Vec<ClientUpdate>, Box<dyn std::error::Error>> {
        let mut client_updates = Vec::new();
        let timeout_duration = Duration::from_secs(300); // 5 minute timeout
        
        for client_id in selected_clients {
            // Wait for client to complete training and send update
            let update = tokio::time::timeout(
                timeout_duration,
                self.receive_client_update(&client_id)
            ).await;
            
            match update {
                Ok(Ok(client_update)) => {
                    client_updates.push(client_update);
                },
                Ok(Err(e)) => {
                    eprintln!("Error receiving update from client {}: {}", client_id, e);
                },
                Err(_) => {
                    eprintln!("Timeout waiting for update from client {}", client_id);
                    // Mark client as potentially slow or unavailable
                    self.mark_client_slow(&client_id);
                }
            }
        }
        
        Ok(client_updates)
    }
    
    fn aggregate_client_models(&self, updates: Vec<ClientUpdate>) -> Result<Vec<f32>, Box<dyn std::error::Error>> {
        match self.aggregation_strategy {
            AggregationStrategy::FederatedAveraging => {
                self.federated_averaging(updates)
            },
            AggregationStrategy::WeightedAveraging => {
                self.weighted_averaging(updates)
            },
            AggregationStrategy::MedianAggregation => {
                self.median_aggregation(updates)
            }
        }
    }
    
    fn federated_averaging(&self, updates: Vec<ClientUpdate>) -> Result<Vec<f32>, Box<dyn std::error::Error>> {
        if updates.is_empty() {
            return Err("No client updates to aggregate".into());
        }
        
        let weight_size = updates[0].model_weights.len();
        let mut aggregated_weights = vec![0.0; weight_size];
        
        // Calculate total samples across all clients
        let total_samples: usize = updates.iter().map(|u| u.num_samples).sum();
        
        // Weighted average based on number of samples
        for update in updates {
            let weight = update.num_samples as f32 / total_samples as f32;
            
            for i in 0..weight_size {
                aggregated_weights[i] += weight * update.model_weights[i];
            }
        }
        
        Ok(aggregated_weights)
    }
    
    fn weighted_averaging(&self, updates: Vec<ClientUpdate>) -> Result<Vec<f32>, Box<dyn std::error::Error>> {
        // Similar to federated averaging but uses client-reported performance metrics
        let weight_size = updates[0].model_weights.len();
        let mut aggregated_weights = vec![0.0; weight_size];
        
        // Calculate weights based on inverse of client loss (better performance = higher weight)
        let total_weight: f32 = updates.iter()
            .map(|u| 1.0 / (u.training_loss + 1e-8))
            .sum();
        
        for update in updates {
            let weight = (1.0 / (update.training_loss + 1e-8)) / total_weight;
            
            for i in 0..weight_size {
                aggregated_weights[i] += weight * update.model_weights[i];
            }
        }
        
        Ok(aggregated_weights)
    }
    
    fn apply_differential_privacy(&self, weights: Vec<f32>) -> Result<Vec<f32>, Box<dyn std::error::Error>> {
        let mut private_weights = weights;
        
        match self.noise_mechanism {
            NoiseDistribution::Gaussian { sigma } => {
                let mut rng = rand::thread_rng();
                let normal = Normal::new(0.0, sigma).unwrap();
                
                for weight in &mut private_weights {
                    let noise: f32 = normal.sample(&mut rng) as f32;
                    *weight += noise;
                }
            },
            NoiseDistribution::Laplace { scale } => {
                let mut rng = rand::thread_rng();
                
                for weight in &mut private_weights {
                    let u1: f32 = rng.gen_range(0.0..1.0);
                    let u2: f32 = rng.gen_range(0.0..1.0);
                    
                    let laplace_noise = if u1 < 0.5 {
                        scale * (2.0 * u1).ln()
                    } else {
                        -scale * (2.0 * (1.0 - u1)).ln()
                    };
                    
                    *weight += laplace_noise;
                }
            }
        }
        
        Ok(private_weights)
    }
}

#[derive(Clone)]
struct ClientUpdate {
    client_id: String,
    model_weights: Vec<f32>,
    num_samples: usize,
    training_loss: f32,
    training_accuracy: f32,
    computation_time: Duration,
}

#[derive(Clone)]
enum AggregationStrategy {
    FederatedAveraging,
    WeightedAveraging,
    MedianAggregation,
}

pub struct FederatedClient {
    client_id: String,
    local_model: Network,
    local_data: Vec<(Vec<f32>, Vec<f32>)>,
    server_addr: String,
    privacy_level: PrivacyLevel,
}

impl FederatedClient {
    pub async fn participate_in_round(&mut self) -> Result<(), Box<dyn std::error::Error>> {
        // Receive global model from server
        let global_weights = self.receive_global_model().await?;
        self.local_model.set_weights(&global_weights)?;
        
        // Train locally
        let training_start = Instant::now();
        let (loss, accuracy) = self.train_local_model().await?;
        let training_time = training_start.elapsed();
        
        // Prepare model update
        let mut updated_weights = self.local_model.get_weights();
        
        // Apply local differential privacy if requested
        if let PrivacyLevel::Local { epsilon } = self.privacy_level {
            updated_weights = self.apply_local_privacy(updated_weights, epsilon)?;
        }
        
        // Send update to server
        let update = ClientUpdate {
            client_id: self.client_id.clone(),
            model_weights: updated_weights,
            num_samples: self.local_data.len(),
            training_loss: loss,
            training_accuracy: accuracy,
            computation_time: training_time,
        };
        
        self.send_update_to_server(update).await?;
        
        Ok(())
    }
}
```

This comprehensive Code Examples document provides practical, production-ready examples covering all major aspects of the ruv-FANN framework, from basic neural networks to advanced distributed training scenarios. Each example includes detailed implementations with proper error handling and modern Rust patterns.