A dependently-typed deep learning framework for Lean 4, providing compile-time tensor shape verification. Very much WIP.

Tyr uses Lean 4's dependent type system to catch tensor dimension mismatches at compile time, not runtime. This eliminates a major source of bugs while providing access to optimized tensor operations.

-- Shapes are tracked in the type system
def linear {m n b : UInt64} (x : T #[b, m]) (M : T #[n, m]) : T #[b, n] := ...

-- Mismatched dimensions fail at compile time, not runtime!
let x : T #[32, 768] := ...
let w : T #[768, 512] := ...
let y := linear x w  -- Error: expected T #[n, 768], got T #[768, 512]

Install elan (the Lean version manager):

curl https://raw.githubusercontent.com/leanprover/elan/master/elan-init.sh -sSf | sh

The correct Lean nightly is pinned in lean-toolchain and will be installed automatically on first lake build.

macOS:

cd external
LIBTORCH_VERSION=2.10.0
curl --fail --location --retry 5 --retry-all-errors --show-error \
  -o libtorch.zip "https://download.pytorch.org/libtorch/cpu/libtorch-macos-arm64-${LIBTORCH_VERSION}.zip"
unzip -tq libtorch.zip
unzip -q libtorch.zip && rm libtorch.zip
cd ..

Or run the helper script:

bash dependencies_macos.sh

Linux (CPU):

cd external
LIBTORCH_VERSION=2.10.0
curl --fail --location --retry 5 --retry-all-errors --show-error \
  -o libtorch.zip "https://download.pytorch.org/libtorch/cpu/libtorch-shared-with-deps-${LIBTORCH_VERSION}%2Bcpu.zip"
unzip -tq libtorch.zip
unzip -q libtorch.zip && rm libtorch.zip
cd ..

Linux (CUDA 12.6):

cd external
curl -O https://download.pytorch.org/libtorch/nightly/cu126/libtorch-cxx11-abi-shared-with-deps-latest.zip
unzip libtorch-cxx11-abi-shared-with-deps-latest.zip && rm libtorch-cxx11-abi-shared-with-deps-latest.zip
cd ..

macOS (Homebrew):

brew install libomp

Linux: OpenMP is typically included with GCC. Install if needed:

sudo apt install libomp-dev   # Debian/Ubuntu

macOS:

brew install apache-arrow

Linux:

sudo apt install libarrow-dev libparquet-dev

• macOS: Xcode command line tools (xcode-select --install)
• Linux: GCC 9+ or Clang 10+ (sudo apt install build-essential)

# Build all targets with Lake
lake build

# Build specific executables
lake build test_runner
lake build TrainGPT
lake build TrainDiffusion
lake build TrainNanoChat
lake build FluxDemo

All executables need the native library paths set at runtime:

macOS (Apple Silicon):

export DYLD_LIBRARY_PATH=external/libtorch/lib:/opt/homebrew/opt/libomp/lib:/opt/homebrew/lib

macOS (Intel):

export DYLD_LIBRARY_PATH=external/libtorch/lib:/usr/local/opt/libomp/lib:/usr/local/lib

Linux:

export LD_LIBRARY_PATH=external/libtorch/lib:/usr/lib

Or use the Lake helper scripts which set these automatically:

lake run           # runs test_runner
lake run train     # runs TrainGPT

lake build test_runner
.lake/build/bin/test_runner

# Or use the helper script
lake run

# Experimental/in-progress suites
lake build test_runner_experimental
.lake/build/bin/test_runner_experimental

See Examples/README.md for detailed per-example documentation.

Use the helper scripts to run TrainNanoChat under torchrun without pulling in a mismatched CUDA module stack:

# default: debug smoke run on 2 GPUs
./scripts/nanochat/run_train_torchrun.sh

# explicit 4-GPU run
NPROC_PER_NODE=4 ./scripts/nanochat/run_train_torchrun.sh \
  --debug --iterations 2 --data data/nanochat --val data/nanochat

# scaling check (1/2/4 GPUs by default)
./scripts/nanochat/bench_distributed.sh

Notes:

• run_train_torchrun.sh defaults TORCHRUN_BIN to /grid/it/data/elzar/easybuild/software/Anaconda3/2023.07-2/bin/torchrun.
• Override launcher path with TORCHRUN_BIN=/path/to/torchrun.
• Override process counts in the benchmark script with SIZES="2 4" (or any space-separated list).

The ThunderKittens-style GPU coverage now has a reusable end-to-end parity path centered on seeded fixture generation plus hardware-backed validation:

# Run the current GPU parity suite
./scripts/gpu/test_parity_suite.sh

# Add randomized MHA trials on top of the deterministic suite
RANDOMIZED_MHA_TRIALS=10 ./scripts/gpu/test_parity_suite.sh

Notes:

• The suite currently covers copy, rotary, layernorm, flashattn, and mha_h100 entrypoints through the executables declared in lakefile.lean.
• PyTorch is the default numerical oracle for fixture generation and parity.
• If you have a local vendored ThunderKittens reference runner, set TYR_GPU_VENDORED_REF_RUNNER=/path/to/runner. It will be called as runner <suite-name> <fixture-dir> after each suite and should exit nonzero on mismatch.
• This checkout may have an empty thirdparty/ThunderKittens directory; the vendored hook is optional and exists so parity can start paying off before the submodule/runtime reference path is fully wired.

The core data type is T s - a tensor type indexed by its shape:

-- T is parameterized by shape (Array UInt64)
def T (s : Shape) : Type := TSpec.type

-- Shape mismatches are compile-time errors
def matmul {a b c : UInt64} (x : T #[a, b]) (y : T #[b, c]) : T #[a, c] := ...

Generic traversal over structures containing tensors:

class TensorStruct (α : Type) where
  map     : (∀ {s}, T s → T s) → α → α
  mapM    : (∀ {s}, T s → m (T s)) → α → m α
  zipWith : (∀ {s}, T s → T s → T s) → α → α → α
  fold    : (∀ {s}, T s → β → β) → β → α → β

Use Vector n α instead of Array α for type-safe zipWith operations.

Two patterns for different use cases:

-- Fixed dimensions (type-safe):
let iter := SequentialBatchIterator.new loader 8 256
let (batch, iter') := iter.next  -- Returns T #[8, 256]

-- Dynamic dimensions:
let iter := BatchIterator.new shard 8 256
let (batch, iter') ← iter.next   -- Returns T #[] (erased)

Tyr includes a Lean command-level type provider for SafeTensors schemas:

import Tyr.SafeTensors

open torch

-- Works with a single .safetensors file or a sharded directory.
-- If `model.safetensors.index.json` exists, introspection follows `weight_map`.
safetensors_type_provider "/path/to/model_dir_or_file" as ModelWeights

def inspectWeights : IO Unit := do
  IO.println s!"discovered tensors: {ModelWeights.tensorCount}"

  -- Per-tensor typed loader + typed schema metadata
  let tokEmbed ← ModelWeights.load_model_embed_tokens_weight
  IO.println s!"embed dtype: {ModelWeights.model_embed_tokens_weightSpec.dtype}"
  IO.println s!"embed shape: {tokEmbed.runtimeShape}"

  -- Hierarchical aggregate generated from tensor names
  let weights ← ModelWeights.loadAll
  let qProj := weights.model.layers[0]!.self_attn.q_proj.weight
  IO.println s!"q_proj shape: {qProj.runtimeShape}"

  -- Hierarchical subtree loaders are also generated
  let decoder ← ModelWeights.model.load
  IO.println s!"loaded subtree"

Notes:

• Tensor schema dtype metadata uses the core torch.DType type (not raw strings).
• For sharded checkpoints, unsafe index shard paths (absolute paths or .. traversal) are rejected.

The C++ bindings use careful reference counting. See cc/src/tyr.cpp header for details:

• borrowTensor(): Shared ownership, auto-cleanup
• giveTensor(): Transfer ownership to Lean
• lean_dec(): Required after extracting from lean_obj_arg, not for b_lean_obj_arg

Monitor tensor leaks via get_live_tensors which tracks outstanding C++ tensors.

1. Add Lean declaration in Tyr/Torch.lean with @[extern "lean_torch_xxx"]
2. Implement in cc/src/tyr.cpp following reference counting conventions
3. Rebuild: lake build

• lakefile.lean - Lake build configuration
• lean-toolchain - Lean version specification
• cc/ - C++ FFI bindings (LibTorch wrapper)
• Tyr/ - Core framework (tensors, modules, optimizers, distributed)
• Examples/ - Training scripts and model implementations
• Tests/ - Test suites

This repo uses scoped conventional commit subjects:

type(scope): summary

A commit message template is included at .gitmessage. Enable it locally:

./scripts/setup-git-hooks.sh

This sets:

• commit.template=.gitmessage
• core.hooksPath=.githooks

Included hooks:

• pre-commit: fails on staged whitespace errors and conflict markers
• commit-msg: enforces type(scope): summary (e.g. feat(qwen35): add video stream patchify)
• pre-push: validates pushed commit subjects with scripts/check-commit-messages.sh

CI also enforces commit subjects using scripts/check-commit-messages.sh.

Manual check examples:

./scripts/check-commit-messages.sh HEAD~20..HEAD
COMMIT_MSG_ENFORCE_FROM=<commit> ./scripts/check-commit-messages.sh HEAD~20..HEAD

TBD.