TorchBurn

A Hardware-Agnostic, High-Performance PyTorch Compilation Backend in Rust
Zero-Copy DLPack FFI, BLAKE3 Graph Caching, Single-Pass Kernel Loop Fusion & Multi-Engine Execution.

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⚡ What is TorchBurn?

TorchBurn bridges PyTorch's compiler frontend (torch.compile) with a high-performance, multi-engine Rust backend. By default, it compiles PyTorch computation graphs into zero-copy, cache-optimized Native CPU kernels using Rayon chunked parallelism and AVX2/NEON SIMD vectorization. It also provides plug-and-play support for Burn's CPU engine (burn_ndarray) and Universal GPU engine (burn_wgpu across Vulkan, DirectX 12, Metal, and WebGPU) with zero CUDA installation required.

Tensors cross the Python ↔ Rust boundary zero-copy using the open DLPack standard, graph DAGs are cached with BLAKE3 structural hashing, and unsupported operators safely fall back to eager PyTorch.

import torch
import torchburn  # Automatically registers the "torchburn" backend

model = torch.nn.Sequential(
    torch.nn.Linear(512, 1024),
    torch.nn.ReLU(),
    torch.nn.Linear(1024, 256),
).eval()

# One line to compile: runs on native CPU by default, or opt into WGPU
compiled_model = torch.compile(model, backend="torchburn")
output = compiled_model(torch.randn(32, 512))

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🧠 Universal LLM Engine (Zero CUDA, Zero llama.cpp)

TorchBurn v0.5.5 introduces torchburn.LLM: a high-level, universal language model inference engine that runs any model directly from Hugging Face Hub or local checkpoints with 5–9 lines of code.

• No CUDA, No llama.cpp, No GGUF conversion: Executes directly on raw PyTorch weights (.safetensors).
• Hardware Auto-Dispatch: Seamlessly dispatches across all hardware:
  • CPUs: AVX-512 VNNI / AVX2 / ARM NEON with pure-Rust decoders (up to 76.5 tokens/sec).
  • iGPUs & dGPUs: Intel Iris Xe, AMD Radeon, Apple Silicon, and NVIDIA via the End-to-End WGPU Compute Graph Decoder (Vulkan) with 1-shot command stream submission (up to 23.3 tokens/sec on Intel Iris Xe).
• Hugging Face Hub Integration: Direct loading with automatic token discovery (token="...", HF_TOKEN, or huggingface-cli login cache).
• Universal Quantization: INT4 SIMD (W4A32), INT8, and FP32.

5-Line Generation

import torchburn as tb

# Load any Hugging Face or local model in 1 line
llm = tb.LLM.from_pretrained("Qwen/Qwen2.5-0.5B-Instruct", quant="int4", device="auto")

# Generate completion in 1 line
print(llm.generate("Explain quantum computing in two sentences."))

Real-Time Streaming

import torchburn as tb

llm = tb.LLM.from_pretrained("Qwen/Qwen2.5-0.5B-Instruct", quant="int4")
for token in llm.stream("Once upon a time in a digital kingdom:"):
    print(token, end="", flush=True)

Interactive Multi-Turn Chat

import torchburn as tb

llm = tb.LLM.from_pretrained("Qwen/Qwen2.5-0.5B-Instruct", quant="int4")
llm.chat(system_prompt="You are a helpful and concise AI.")

Command-Line CLI

# Interactive chat in your terminal
python -m torchburn.llm chat --model Qwen/Qwen2.5-0.5B-Instruct --quant int4

# Single prompt generation
python -m torchburn.llm generate "Explain black holes" --model models/qwen_0_5b --stream

# Hardware benchmark (measures tok/s and latency)
python -m torchburn.llm benchmark --model models/qwen_0_5b --device cpu --tokens 64

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🚀 Key Highlights (v0.6.1)

• 🔥 Peak-Optimization Release (v0.6.1): fat LTO + codegen-units=1 release profile, portable per-target baselines (x86-64-v2 / neoverse-n1 / apple-m1 / apple-a14) with runtime AVX2/AVX-512-VNNI/NEON dispatch, cached CPUID (no per-row CPUID), vectorized m==1 GEMV (f32x8 FMA), lock-optimized BLAKE3 cache, per-bucket memory pooling, and allocation-free contiguity checks. Prebuilt wheels ship for Windows AMD64, Linux x86_64+aarch64, macOS arm64+x86_64 (plus CUDA and native variants) — see CHANGELOG.
• ⚡ Native CPU by Default: Out-of-the-box zero-copy execution on CPU with zero GPU setup or shader compilation delays. Reaches 98.2% parity with Intel MKL on $1024^3$ GEMM (12.29 ms vs 12.08 ms), with -48.5% GEMM improvement in v0.5.5.
• 🔄 Single-Pass Kernel Loop Fusion: Fuses multi-node unary/binary DAGs into single memory sweeps with stack-allocated [T; 32] scratch space, eliminating heap allocations in worker threads.
• 🏎️ Chunked SIMD Parallelization: Rayon L1/L2-aware chunking (PAR_CHUNK = 16 * 1024) with wide f32x8 vectorized polynomials for GELU (7.7× speedup: 9.83 ms → 1.28 ms), sigmoid, tanh, silu, and softmax.
• 📦 Prepared Graph Pre-Planning: prepare_graph() pre-plans memory slot assignments and fusion plans once, skipping graph traversal and HashMap lookups on every forward pass.
• 🧮 Parallel Epilogue Fusion: Fuses Linear and GEMM activation epilogues (ReLU, GELU, Sigmoid, SiLU) directly into multi-threaded chunked matrix output writes.
• 🎮 Multi-Engine Flexibility: Seamlessly toggle between native_cpu, burn_ndarray, and burn_wgpu (Vulkan / DX12 / Metal).
• 🧬 BLAKE3 Structural Graph Caching: Nanosecond-level cache lookups with LRU promotion bypass re-tracing overhead on warm runs.
• 🛡️ Safe Eager Fallback: Unrecognized nodes fall back with bounded warnings and op_coverage() telemetry.
• 🔒 100% Test Passing: Comprehensive test coverage across 450 native operators verified against PyTorch ground truth.
• 🚀 O(1) Dispatch: HashMap-based operator dispatch replaces 22-module linear scan, eliminating per-node string comparison overhead.
• 🧵 Rayon-Parallel Kernels: Losses, embedding, matmul backward, softmax, and gradient accumulation all parallelized via rayon for large tensors.
• 🎯 Zero-Copy View Cloning: Arc<[i64]> slot views eliminate Vec clone overhead on every node execution.

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🏛️ Multi-Engine Architecture: Why 3 Engines?

TorchBurn features 3 distinct execution engines tailored for different deployment environments:

1. native_cpu (Default):
   • Characteristics: Hand-tuned Rust kernels using rayon, matrixmultiply, and wide f32x8 SIMD.
   • Best For: Maximum single-node and server CPU inference throughput, zero dependencies, instant execution.
2. burn_ndarray (Pure Rust CPU Engine):
   • Why is it needed?:
     • Golden Reference: 100% safe, pure-Rust fallback with zero C/CBLAS dependencies, critical for cross-compilation (e.g., embedded, WASM, musl).
     • Headless CI Stability: Provides a reliable CPU fallback in headless CI runners where virtualized GPU/Metal drivers return uninitialized buffers.
     • Burn Ecosystem Interoperability: Allows direct bridge and graph execution within Burn's native training/deployment pipeline.
3. burn_wgpu (Universal GPU Acceleration):
   • Characteristics: WebGPU compute shaders executing across AMD, Intel, Apple Silicon, and NVIDIA via Vulkan, DirectX 12, or Metal.
   • Best For: GPU acceleration on consumer hardware without installing multi-gigabyte CUDA toolkits.

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📊 Performance Benchmarks (v0.5.5 Native CPU vs Intel MKL / PyTorch Eager)

System: Intel Core i7-11800H @ 2.30 GHz (8 cores / 16 threads), Windows 11 x86_64, FP32

Workload	PyTorch Eager (MKL/AVX2)	TorchBurn native_cpu	Status / Ratio	v0.5.5 Improvement
GEMM $1024 \times 1024 \times 1024$	12.08 ms	13.5 ms	89.5% Parity	-48.5% vs v0.5.4 (26.2 ms)
GEMM $256 \times 256 \times 256$	—	328 µs	—	-24.7% vs v0.5.4
GELU Activation ($1024^2$)	0.94 ms	1.28 ms	1.36× of eager	7.7× faster vs pre-chunked
Multi-Head Attention ($B=4, H=8, T=128, D=64$)	0.93 ms	1.13 ms	82.2% Parity	Zero-copy QKV projection
Linear + Epilogue ($128 \times 512 \to 1024$)	0.35 ms	0.55 ms	1.57× of eager	Vectorized parallel epilogue
Softmax ($2048 \times 2048$)	8.12 ms	8.84 ms	91.8% Parity	SIMD-accelerated (new in v0.5.5)
Decoder Step (Qwen 0.5B int4)	—	3.46 ms/token	—	-9.7% vs v0.5.4

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⚙️ Device & Engine Selection

TorchBurn executes on native_cpu by default. You can easily inspect or customize execution target via environment variables or Python API:

import torchburn

# Check active execution engine
print(torchburn.active_engine())  # 'native_cpu' (default), 'burn_ndarray', or 'burn_wgpu'

Note: engine selection is process-wide and read at import time — set TORCHBURN_ENGINE before your script starts (see table below).

Environment Variable Controls

Environment Variable	Allowed Values	Description
TORCHBURN_ENGINE	native_cpu (default), burn, burn-wgpu	Explicitly select execution backend
TORCHBURN_DEVICE	cpu (default), gpu	High-level device target switch
TORCHBURN_WGPU_BACKEND	vulkan, dx12, metal, gl	Force specific graphics API for WGPU

Run with WGPU acceleration:

TORCHBURN_ENGINE=burn-wgpu python your_model.py

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🏗️ Architecture & Data Flow

   torch.compile(model, backend="torchburn")
                     │
                     ▼
          torch._dynamo / FX Graph
                     │
                     ▼
       TorchBurn FX Partitioning Engine
        ┌────────────┴────────────┐
        │                         │
        ▼                         ▼
   Supported Nodes         Unsupported Nodes
   (130+ ops)                     │
        │                         ▼
        │                 Safe Eager Fallback
        ▼                 (Ground-truth PyTorch)
   Zero-Copy DLPack FFI (`engine.rs:753` `allow_threads`)
         │
         ▼
     Rust Execution Core (release):
     ├── O(1) HashMap Dispatch `dispatch_op.rs` `OnceLock<HashMap>`
     ├── BLAKE3 LRU Cache `cache.rs:23` 1024 + `pool.rs:34` best-fit MaybeUninit
     ├── L1 16KB + `wide f32x8` SIMD `ops.rs:22` + online softmax `activations.rs:270`
     ├── Rayon-parallel losses/embedding/matmul/softmax/gradient-accum
     ├── OpenBLAS Skylake `blas.rs:7` + `matrixmultiply` tiled GEMM `linalg.rs:1`
     ├── Fusion `fusion.rs:55` `ConvBnRelu` + QKV+softmax+V (v2)
     └── Burn WGPU 16×16 tiled `wgpu_kernels/matmul.wgsl` vec4 shaders LRU `wgpu_backend.rs:179`
        │
        ▼
   Zero-Copy DLPack Output Capsules ──► torch.Tensor

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🧩 Supported Operators (450 wired – v0.4.1)

Click to expand full operator matrix (450)

Category	Operators	Count
Elementwise	add, sub, mul, div, neg, reciprocal, abs, sign, clamp, fmod, remainder, bitwise_and/or/xor/not, copysign, ldexp, nextafter, heaviside, isclose, allclose, equal, isreal, is_complex	32
Math & Transcendentals	exp, exp2, expm1, log, log2, log10, log1p, sqrt, rsqrt, square, pow, sin, cos, tan, asin, acos, atan, sinh, cosh, tanh, erf, erfc, asinh, acosh, atanh, sinc, i0/i1/i0e/i1e, bessel_j0/j1/y0/y1, digamma, lgamma, polygamma, mvlgamma, erfinv, erfcinv, ndtri, ndtr, log_ndtr, logit, expit, rad2deg, deg2rad, trunc, frac, logspace, eye, diag, triu/tril	58
Activations	relu, sigmoid, tanh, gelu, silu, leaky_relu, elu, selu, softplus, mish, softmax, log_softmax, hardtanh, hardsigmoid, glu, celu, hardshrink, softshrink, tanhshrink, threshold, logsigmoid, rrelu, bernoulli, multinomial	24
Linear Algebra	linear, matmul, bmm, addmm, dot, t, transpose, mv, vdot, baddbmm, addbmm, addmv, kron, inner, outer, linalg_multi_dot, linalg_vander, linalg_vecdot, linalg_cross, linalg_tensordot, linalg_norm, frobenius_norm, nuclear_norm, matrix_rank, cholesky, qr, svd, eig, lu	32
Reductions	sum, mean, max, min, argmax, argmin, std, var, var_mean, std_mean, prod, cumsum, all, any, amax, amin, count_nonzero, nansum, nanmean, nanprod, nanmin, nanmax, nanmedian, cummax, cummin, logcumsumexp, logsumexp, cov, corrcoef	30
Normalization	layer_norm, batch_norm, group_norm, rms_norm, instance_norm, local_response_norm, channel_shuffle	7
Shape & Indexing	reshape, view, view_as, permute, squeeze, unsqueeze, expand, expand_as, broadcast_to, broadcast_tensors, flatten, cat, stack, split, chunk, vsplit, hsplit, dsplit, tensor_split, unbind, select, narrow, gather, index_select, take_along_dim, index_reduce, scatter_max/min, tile, roll, pixel_shuffle, unfold, fold, pixel_unshuffle, grid_sample, affine_grid, as_strided, empty_strided, take, put, index_fill, masked_select/scatter, index_add/put	45
Convolution & Pooling	conv1d, conv2d, conv3d, conv_transpose1d, conv_transpose2d, conv_transpose3d, max_pool1d, max_pool2d, max_pool3d, avg_pool1d, avg_pool2d, avg_pool3d, adaptive_avg/max_pool1d/2d/3d, fractional_max_pool2d/3d, lp_pool1d/2d/3d, max_unpool1d/2d/3d	28
Transformer/LLM	scaled_dot_product_attention, flash_attention, fused_swiglu/geglu/rmsnorm_residual, embedding, embedding_bag, rope, multi_head_attention_forward, lstm/gru/rnn_cells	12
Losses	mse_loss, huber_loss, smooth_l1_loss, cross_entropy, nll_loss, binary_cross_entropy, kl_div, poisson_nll, margin_ranking, hinge_embedding, soft_margin, cosine_embedding, triplet_margin, ctc_loss, bincount, unique, kthvalue, median, histogram, bucketize, searchsorted, meshgrid	22
Creation/Quant/FFT	full, zeros, ones, arange, linspace, rand/randn/randint/randperm, empty, zeros_like, ones_like, full_like, randn_like, rand_like, randint_like, eye, diag, hann/bartlett/blackman/hamming/kaiser/gaussian windows, stft, istft, quantize/dequantize_per_tensor/channel, int8_gemm, nf4_dequantize, fft, ifft, rfft, irfft, fft2, ifft2, fftn, ifftn, fftshift, ifftshift, complex, real, imag, angle, polar, conj	42

See docs/ops_coverage.md for full signatures and test coverage metrics.

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🚀 Performance Roadmap

The full phased plan for kernel/backend optimization (CPU int4 GEMV, iGPU latency, CUDA backend, GGUF import, speculative decoding) with measured baselines and benchmark gates lives in docs/OPTIMIZATION_ROADMAP.md.

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📦 Wheels (v0.6.1)

Prebuilt portable wheels are published to PyPI on every v* tag (see CHANGELOG.md). Baselines are portable; faster ISA paths (AVX2/AVX-512-VNNI/NEON) are selected at runtime:

Platform	Architectures	Notes
Windows	AMD64 (x86-64-v2)	Vulkan/DX12 via burn-wgpu
Linux	x86_64 (x86-64-v2), aarch64 (neoverse-n1)	Vulkan; CUDA wheel from cuda-build job
macOS 11+	arm64 (apple-m1), x86_64 (x86-64-v2)	Metal / Vulkan
Native (self-hosted)	host (target-cpu=native)	Peak bench wheel, not for PyPI

pip install torchburn  # portable optimized wheel

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🧪 Testing & Validation

TorchBurn 450 native ops, 553 tests (test_all_450_ops.py 450 distinct), validate_450.py 48/48 batch4 pass torch.allclose(atol=1e-4):

# Run full 450-op sweep (release)
python -m pytest tests/test_all_450_ops.py -q  # 450 distinct
python -m pytest tests/ -q  # 553 passed, 5 deselected (BertTiny/BenchmarkSuite)

# Validate batch4 48 vs PyTorch
python validate_450.py  # 48/48 PASS

# Force CPU or GPU
TORCHBURN_DEVICE=cpu python -m pytest tests/ -q
TORCHBURN_DEVICE=gpu python bench_full.py  # Iris Xe Vulkan 134ms softmax

# Lints
cargo clippy -- -D warnings
cargo fmt --check

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📄 License

TorchBurn is open-source software licensed under the Apache 2.0 License. See LICENSE for details.