lattice-inference — Contributor Map

Stability tier: Experimental. This crate has high churn, 153 unsafe blocks, and 22 dead_code_allows. It is NOT intended for direct use by platform or feature crates. Consumers should go through lattice-embed. The unsafe blocks are documented in foundation/STABILITY.md §Tech Debt. Tracking issue: #1306. See foundation/STABILITY.md for the full stability policy.

If you are trying to generate embeddings in an application, start with lattice-embed, not this crate. The README you are reading is a contributor's map for people opening PRs on the inference engine itself.

Module Map

Grouped modules

These modules contain submodules (directories with their own mod.rs).

Module	Responsibility
`attention`	Attention kernel variants: standard MHA, GQA, flash (CPU tiled), flash-causal (decoder prefill), GDN (gated decay network), GDN-fused, native sparse, and differential. Exposes `AttentionTag` for typed dispatch.
`forward`	Compute backends: scalar CPU, NEON (AArch64), Metal (macOS MSL), WGPU, Q8/f16 CPU kernels, tiled GEMM (`metal_gemm`, `gpu_gemm`), batched prefill, and BitNet kernel. Exports `matmul_bt`, `rms_norm`, `silu_inplace`, `elementwise_mul` from the CPU submodule.
`model`	Model configs and loaders: `BertModel`/`BertConfig`, `QwenModel`/`QwenConfig`, `Qwen35Model`, `CrossEncoderModel`, `BitNet` config. Each submodule owns its safetensors load path and forward-pass dispatch.
`tokenizer`	Tokenizer implementations: `WordPieceTokenizer` (BERT), `BpeTokenizer` (Qwen3/GPT-2 byte-level), `SentencePieceTokenizer`. Shared `Tokenizer` trait and `load_tokenizer` auto-detect helper live in `tokenizer/common.rs`.
`vision`	Qwen3-VL vision encoder (ADR-049): ViT forward pass, patch preprocessing, MLP merger, `MultimodalInput` type. CPU-only; Metal GPU path is deferred.
`weights`	Weight storage formats (`Tensor2D`), safetensors memory-mapped loading, f32/f16/Q8/Q4 weight structs, sharded-checkpoint support.

Standalone modules

Module	Responsibility
`batch`	Continuous batching engine (ADR-048): `BatchWorker`, `FifoScheduler`, `Sequence`, `SequenceManager`, chunked prefill interleaved with decode steps.
`download`	Model file cache and conditional download (`ensure_model_files`). Disabled unless the `download` feature is enabled.
`error`	`InferenceError` — the crate's single error type, re-exported at the crate root. Stable; adding variants is backward-compatible.
`grammar`	Grammar-constrained decoding (ADR-046): `GrammarEngine` compiles a JSON Schema or GBNF spec to a byte-level PDA, then masks logits via `mask_logits` and advances state via `advance` each decode step.
`kv_cache`	Two KV cache implementations: `FlatKVCache` (contiguous pre-allocated, single request) and `PagedKVCache` (256-token pages, LRU eviction, multi-model serving). Includes `PrefixPageCache` for prefix reuse.
`lora_hook`	`LoraHook` trait: defines the `apply(layer_idx, module, x, output)` contract that the forward pass calls after each linear projection. `NoopLoraHook` is the zero-overhead default.
`metrics`	Inference metrics (ADR-061): `MetricsMode` enum and `LayerMetrics` schema. Zero overhead when `MetricsMode::Off`.
`pool`	Pooling strategies for producing a single embedding vector: `BertPooling` (Mean or CLS), `mean_pool`, `cls_pool`, `last_token_pool` (Qwen3), `l2_normalize`.
`pruning`	ShortGPT block-influence scorer (ADR-060 D2 seed): `BlockInfluenceAccumulator` and `BlockInfluence`. Standalone math; the calibration pipeline hooks are future work.
`quant`	Quantization pre-transforms: `quarot` (Walsh-Hadamard rotation primitives, ADR-044). Not yet wired into the Q4 weight path.
`rope`	Rotary position embeddings: `RopeTable` precomputes sin/cos tables and applies them in-place to Q and K slices before attention.
`sampling`	Token sampling for generation: `Sampler`, `SamplingConfig` (temperature, top-k, top-p, repetition penalty).
`speculative`	N-gram prompt-lookup speculative decoding: `NgramSpeculator::speculate` + `verify_draft` (low-level) and `generate_with_speculation` (high-level wrapper).

Feature-gated modules

Module	Feature flag	Responsibility
`mixture`	`mixture`	Adapter routing and mixture-of-LoRA support layered on top of `lora_hook`.
`backward`	`train-backward`	Reverse-mode autodiff for LoRA training: `tape`, `ops`, `attention_gqa`, `gradcheck`. Submodule of `lattice-tune`'s training loop.

Run an Example

Qwen3.5 text generation demo (src/bin/qwen35_generate.rs):

cargo run --release -p lattice-inference --bin qwen35_generate -- \
  --model-dir PATH --prompt "Hello" --max-tokens 64 --seed 42

Qwen3 embedding benchmark (examples/bench_embedding.rs, registered in Cargo.toml as an [[example]] target — despite an outdated --bin reference in the file's own header comment, run it with --example):

cargo run --release -p lattice-inference --example bench_embedding --features f16

For the concise forward-pass trace (safetensors load → tokenize → prefill → decode-loop sampling), see docs/architecture.md § Forward Pass Pipeline. A deeper Qwen3.5-specific walkthrough lives in docs/forward-pass.md.

Supported Architectures

Architecture	Submodule	Notes
BERT / BGE (encoder-only)	`model/bert.rs`	Bidirectional attention, WordPiece tokenizer, mean or CLS pooling. Covers BGE-small/base/large, E5-small/base, all-MiniLM, paraphrase-multilingual-MiniLM.
Qwen3 / Qwen3.5 (decoder-only)	`model/qwen.rs`, `model/qwen35/`	Causal GQA, RoPE, RMSNorm, SwiGLU FFN, BPE tokenizer, last-token pooling. Covers Qwen3-Embedding-0.6B and 4B.
BitNet	`model/bitnet_config.rs`	1.58-bit quantized weight architecture.
Qwen3-VL (vision)	`vision/`	ViT patch encoder + MLP merger for multimodal input; CPU-only (ADR-049 v0 scope).
Cross-encoder	`model/cross_encoder.rs`	BERT-style reranker with a classification head on top of the CLS token.

Where to Start for Common PR Types

New model architecture. Add a submodule under model/ following the pattern in model/qwen.rs (config struct, weights struct, load function, encode/forward method). Wire the new architecture into lattice-embed's EmbeddingModel enum when ready.

Attention kernel change. Work in attention/ and forward/. A new kernel goes in its own file under attention/ (e.g. attention/flash_causal.rs), registers a variant on AttentionTag, and dispatches from the relevant forward/ backend. See docs/architecture.md for the full forward-pass walkthrough before touching this path.

Sampling or generation. sampling.rs owns the shared Sampler and SamplingConfig primitives. Canonical Qwen3.5 generation lives in model/qwen35/generation.rs, with backend-specific entry points under forward/; grammar-constrained decoding uses the shared grammar module.

LoRA adapter injection. The LoraHook trait in lora_hook.rs is the injection point. The training-side implementation lives in crates/tune. Backward-pass gradients are behind the train-backward feature in backward/.

Quantization. Q4 and Q8 weight structs are in weights/q4_weights.rs and weights/q8_weights.rs. Pre-transform math (QuaRot) is in the quant/quarot/ module (hadamard.rs, convert.rs, pipeline.rs). Wiring QuaRot into the Q4 load path is tracked in ADR-044.

Cross-References

docs/architecture.md — crate dependency graph, design philosophy, and forward-pass pipeline.
AGENTS.md — contribution policy, SIMD verification rules, agent attribution requirements.
docs/adr/INDEX.md — full list of architecture decision records by crate.

lattice-inference 0.7.2