/domain-ml

name: domain-ml
description: "Use when building ML/AI apps in Rust. Keywords: machine learning, ML, AI, tensor, model, inference, neural network, deep learning, training, prediction, ndarray, tch-rs, burn, candle, 机器学习, 人工智能, 模型推理"
user-invocable: false

Machine Learning Domain

> **Layer 3: Domain Constraints**

Domain Constraints → Design Implications

| Domain Rule | Design Constraint | Rust Implication | |-------------|-------------------|------------------| | Large data | Efficient memory | Zero-copy, streaming | | GPU acceleration | CUDA/Metal support | candle, tch-rs | | Model portability | Standard formats | ONNX | | Batch processing | Throughput over latency | Batched inference | | Numerical precision | Float handling | ndarray, careful f32/f64 | | Reproducibility | Deterministic | Seeded random, versioning |

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Critical Constraints

Memory Efficiency

RULE: Avoid copying large tensors
WHY: Memory bandwidth is bottleneck
RUST: References, views, in-place ops

GPU Utilization

RULE: Batch operations for GPU efficiency
WHY: GPU overhead per kernel launch
RUST: Batch sizes, async data loading

Model Portability

RULE: Use standard model formats
WHY: Train in Python, deploy in Rust
RUST: ONNX via tract or candle

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Trace Down ↓

From constraints to design (Layer 2):

"Need efficient data pipelines"
    ↓ m10-performance: Streaming, batching
    ↓ polars: Lazy evaluation

"Need GPU inference"
    ↓ m07-concurrency: Async data loading
    ↓ candle/tch-rs: CUDA backend

"Need model loading"
    ↓ m12-lifecycle: Lazy init, caching
    ↓ tract: ONNX runtime

---

Use Case → Framework

| Use Case | Recommended | Why | |----------|-------------|-----| | Inference only | tract (ONNX) | Lightweight, portable | | Training + inference | candle, burn | Pure Rust, GPU | | PyTorch models | tch-rs | Direct bindings | | Data pipelines | polars | Fast, lazy eval |

Key Crates

| Purpose | Crate | |---------|-------| | Tensors | ndarray | | ONNX inference | tract | | ML framework | candle, burn | | PyTorch bindings | tch-rs | | Data processing | polars | | Embeddings | fastembed |

Design Patterns

| Pattern | Purpose | Implementation | |---------|---------|----------------| | Model loading | Once, reuse | `OnceLock<Model>` | | Batching | Throughput | Collect then process | | Streaming | Large data | Iterator-based | | GPU async | Parallelism | Data loading parallel to compute |

Code Pattern: Inference Server

use std::sync::OnceLock;
use tract_onnx::prelude::*;

static MODEL: OnceLock<SimplePlan<TypedFact, Box<dyn TypedOp>, Graph<TypedFact, Box<dyn TypedOp>>>> = OnceLock::new();

fn get_model() -> &'static SimplePlan<...> {
    MODEL.get_or_init(|| {
        tract_onnx::onnx()
            .model_for_path("model.onnx")
            .unwrap()
            .into_optimized()
            .unwrap()
            .into_runnable()
            .unwrap()
    })
}

async fn predict(input: Vec<f32>) -> anyhow::Result<Vec<f32>> {
    let model = get_model();
    let input = tract_ndarray::arr1(&input).into_shape((1, input.len()))?;
    let result = model.run(tvec!(input.into()))?;
    Ok(result[0].to_array_view::<f32>()?.iter().copied().collect())
}

Code Pattern: Batched Inference

async fn batch_predict(inputs: Vec<Vec<f32>>, batch_size: usize) -> Vec<Vec<f32>> {
    let mut results = Vec::with_capacity(inputs.len());

    for batch in inputs.chunks(batch_size) {
        // Stack inputs into batch tensor
        let batch_tensor = stack_inputs(batch);

        // Run inference on batch
        let batch_output = model.run(batch_tensor).await;

        // Unstack results
        results.extend(unstack_outputs(batch_output));
    }

    results
}

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Common Mistakes

| Mistake | Domain Violation | Fix | |---------|-----------------|-----| | Clone tensors | Memory waste | Use views | | Single inference | GPU underutilized | Batch processing | | Load model per request | Slow | Singleton pattern | | Sync data loading | GPU idle | Async pipeline |

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Trace to Layer 1

| Constraint | Layer 2 Pattern | Layer 1 Implementation | |------------|-----------------|------------------------| | Memory efficiency | Zero-copy | ndarray views | | Model singleton | Lazy init | OnceLock<Model> | | Batch processing | Chunked iteration | chunks() + parallel | | GPU async | Concurrent loading | tokio::spawn + GPU |

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Related Skills

| When | See | |------|-----| | Performance | m10-performance | | Lazy initialization | m12-lifecycle | | Async patterns | m07-concurrency | | Memory efficiency | m01-ownership |