linkedin/Liger-Kernel

Liger Kernel: Efficient Triton Kernels for LLM Training

Stable		Nightly		Discord

Installation | Getting Started | Examples | High-level APIs | Low-level APIs | Cite our work

Liger Kernel is a collection of Triton kernels designed specifically for LLM training. It can effectively increase multi-GPU training throughput by 20% and reduces memory usage by 60%. We have implemented Hugging Face Compatible RMSNorm, RoPE, SwiGLU, CrossEntropy, FusedLinearCrossEntropy, and more to come. The kernel works out of the box with Flash Attention, PyTorch FSDP, and Microsoft DeepSpeed. We welcome contributions from the community to gather the best kernels for LLM training.

We've also added optimized Post-Training kernels that deliver up to 80% memory savings for alignment and distillation tasks. We support losses like DPO, CPO, ORPO, SimPO, KTO, JSD, and many more. Check out how we optimize the memory.

You can view the documentation site for additional installation, usage examples, and API references:https://linkedin.github.io/Liger-Kernel/

You can view the Liger Kernel Technical Report: https://openreview.net/forum?id=36SjAIT42G

Supercharge Your Model with Liger Kernel

With one line of code, Liger Kernel can increase throughput by more than 20% and reduce memory usage by 60%, thereby enabling longer context lengths, larger batch sizes, and massive vocabularies.

Speed Up	Memory Reduction

Note:

• Benchmark conditions: LLaMA 3-8B, Batch Size = 8, Data Type = bf16, Optimizer = AdamW, Gradient Checkpointing = True, Distributed Strategy = FSDP1 on 8 A100s.
• Hugging Face models start to OOM at a 4K context length, whereas Hugging Face + Liger Kernel scales up to 16K.

Optimize Post Training with Liger Kernel

We provide optimized post training kernels like DPO, ORPO, SimPO, and more which can reduce memory usage by up to 80%. You can easily use them as python modules.

from liger_kernel.chunked_loss import LigerFusedLinearORPOLoss
orpo_loss = LigerFusedLinearORPOLoss()
y = orpo_loss(lm_head.weight, x, target)

Examples

Key Features

• Ease of use: Simply patch your Hugging Face model with one line of code, or compose your own model using our Liger Kernel modules.
• Time and memory efficient: In the same spirit as Flash-Attn, but for layers like RMSNorm, RoPE, SwiGLU, and CrossEntropy! Increases multi-GPU training throughput by 20% and reduces memory usage by 60% with kernel fusion, in-place replacement, and chunking techniques.
• Exact: Computation is exact—no approximations! Both forward and backward passes are implemented with rigorous unit tests and undergo convergence testing against training runs without Liger Kernel to ensure accuracy.
• Lightweight: Liger Kernel has minimal dependencies, requiring only Torch and Triton—no extra libraries needed! Say goodbye to dependency headaches!
• Multi-GPU supported: Compatible with multi-GPU setups (PyTorch FSDP, DeepSpeed, DDP, etc.).
• Trainer Framework Integration: Axolotl, LLaMa-Factory, SFTTrainer, Hugging Face Trainer, SWIFT, oumi

Installation

Dependencies

CUDA

• torch >= 2.1.2
• triton >= 2.3.0

ROCm

• torch >= 2.5.0 Install according to the instruction in Pytorch official webpage.
• triton >= 3.0.0 Install from pypi. (e.g. pip install triton==3.0.0)

pip3 install torch torchvision --index-url https://download.pytorch.org/whl/rocm7.2

Ascend NPU

• torch == 2.9.0
• torch_npu == 2.9.0
• triton-ascend == 3.2.2 Install from the Ascend PyPI mirror (not on default PyPI).
• CANN == 9.1.0

pip install -e ".[dev]" --extra-index-url https://triton-ascend.osinfra.cn/pypi/simple

Optional Dependencies

• transformers >= 4.x: Required if you plan to use the transformers models patching APIs. The specific model you are working will dictate the minimum version of transformers.
• cuda-tile: Required when enabling the optional cuTile backend on CUDA. Use this when your environment already provides CUDA Toolkit 13.1 or newer, or an existing tileiras compiler installation.
• cuda-tile[tileiras]: Required when enabling the optional cuTile backend with the tileiras compiler installed directly into your Python environment.
• nvidia-cutlass-dsl >= 4.6.0: Required when enabling the optional CuTe DSL backend on CUDA (the CUDA-only Python DSL shipped with NVIDIA CUTLASS, import cutlass.cute). Targets Hopper (SM90) and Blackwell (SM100/SM110).

Note: Our kernels inherit the full spectrum of hardware compatibility offered by Triton.

To install the stable version:

$ pip install liger-kernel

To install the nightly version:

$ pip install liger-kernel-nightly

To install from source:

git clone https://github.com/linkedin/Liger-Kernel.git
cd Liger-Kernel

# Install Default Dependencies
# Setup.py will detect the local backend and select default dependencies.
# On ROCm, install ROCm PyTorch first from the PyTorch ROCm index.
pip install -e .

# Setup Development Dependencies
pip install -e ".[dev]"

# ROCm source installs
pip3 install torch torchvision --index-url https://download.pytorch.org/whl/rocm7.2
# Then choose one:
pip install -e .
pip install -e ".[dev]"

# Setup cuTile Dependencies
pip install -e ".[cutile]"

# Or install cuTile with the optional tileiras compiler
pip install -e ".[cutile-tileiras]"

# Setup CuTe DSL (NVIDIA CUTLASS Python DSL) Dependencies
pip install -e ".[cutedsl]"

Enable cuTile Backend

cuTile is an optional CUDA-only DSL implementation. After installing the cutile or cutile-tileiras extra, enable it explicitly:

LIGER_KERNEL_IMPL=cutile python your_script.py

LIGER_KERNEL_IMPL selects an opt-in implementation registered with Liger (currently cutile and cutedsl). Selecting one on an unsupported device, or without the required dependencies installed, raises an error.

Enable CuTe DSL Backend

CuTe DSL is the optional, CUDA-only Python DSL shipped with NVIDIA CUTLASS (import cutlass.cute), targeting Hopper (SM90) and Blackwell (SM100/SM110). After installing the cutedsl extra, enable it explicitly:

pip install "liger-kernel[cutedsl]"
LIGER_KERNEL_IMPL=cutedsl python your_script.py

It currently provides genuine cutlass.cute implementations of:

• RMSNorm
• RoPE
• SwiGLU
• Cross entropy
• Fused linear cross entropy (with an SM90-specialized variant)
• Fused scaled cross entropy (SM90)

Ops without a CuTe DSL kernel transparently fall back to the default Triton kernel.

The cutedsl extra also pulls in apache-tvm-ffi, which lets compiled kernels take PyTorch tensors directly rather than marshalling each one per call. It is optional — every kernel falls back to the marshalling launch without it — but short kernels are dominated by that per-call cost, so installing it is strongly recommended.

Fused Scaled Cross Entropy

LigerFusedLinearScaledCrossEntropyFunction is an additional per-token operator, not a replacement for the reduction-oriented Triton LigerFusedLinearCrossEntropyFunction. It takes input[M, H], weight[V, H], and target[M], applies logits / temperature, and returns FP32 negative log-likelihood [M] plus optional differentiable vocabulary entropy [M] in the input dtype. Reductions remain in PyTorch, and rows whose target equals ignore_index contribute zero outputs and gradients.

from liger_kernel.ops import LigerFusedLinearScaledCrossEntropyFunction

nll, entropy = LigerFusedLinearScaledCrossEntropyFunction.apply(
    x, weight, target, 1.0, -100, 1, True
)  # [M], [M]
loss = nll.sum() / (target != -100).sum().clamp_min(1)

The implementations share this public contract but use different schedules:

• cuTile (LIGER_KERNEL_IMPL=cutile) supports matching floating-point input and weight tensors on CUDA and a finite positive scalar temperature. The portable temporary-logits budget is 256 MiB. Large FP16/BF16 Blackwell workloads (M >= 4096, V >= 131072) automatically use 512 MiB to improve GEMM utilization. Set LIGER_CUTILE_SCALED_CE_WORKSPACE_MB to another positive MiB value for workload-specific tuning; for example, 1024 can help large combined NLL-plus-entropy workloads but is not universally faster. Backward reuses one workspace and writes dX and accumulates dW directly into their final tensors. m_tiles_per_cluster is accepted for API compatibility but does not change the cuTile schedule.
• CuTe SM90 uses LigerFusedScaledCrossEntropySM90Function for BF16 inputs on Hopper. Its sole forward uses the fixed cluster-M2 N160 fragment kernel, with a measured split-N lookup for profiled long-sequence shapes, and never writes logits to HBM; m_tiles_per_cluster remains accepted for API compatibility but does not change that schedule. Backward runs dZ, dX, and dW in one persistent cluster kernel with a reusable 1024-token dZ workspace.
• Fallback uses a 512-token chunked PyTorch implementation adapted from Verl's fused PPO formulas when the default frontend cannot use the SM90 kernel.

H100 BF16 forward medians from 60 interleaved samples per provider at H=4096, V=131072. Effective TFLOPS count the common projection work, 2*M*H*V:

Backward medians use 30 interleaved samples per provider. Effective TFLOPS count 6*M*H*V:

Full forward-and-backward effective TFLOPS count 8*M*H*V:

B200 measurements for the same shape, using automatic cuTile workspace selection:

Getting Started

There are a couple of ways to apply Liger kernels, depending on the level of customization required.

1. Use AutoLigerKernelForCausalLM

Using the AutoLigerKernelForCausalLM is the simplest approach, as you don't have to import a model-specific patching API. If the model type is supported, the modeling code will be automatically patched using the default settings.

from liger_kernel.transformers import AutoLigerKernelForCausalLM

# This AutoModel wrapper class automatically monkey-patches the
# model with the optimized Liger kernels if the model is supported.
model = AutoLigerKernelForCausalLM.from_pretrained("path/to/some/model")

2. Apply Model-Specific Patching APIs

Using the patching APIs, you can swap Hugging Face models with optimized Liger Kernels.

import transformers
from liger_kernel.transformers import apply_liger_kernel_to_llama

# 1a. Adding this line automatically monkey-patches the model with the optimized Liger kernels
apply_liger_kernel_to_llama()

# 1b. You could alternatively specify exactly which kernels are applied
apply_liger_kernel_to_llama(
  rope=True,
  swiglu=True,
  cross_entropy=True,
  fused_linear_cross_entropy=False,
  rms_norm=False
)

# 2. Instantiate patched model
model = transformers.AutoModelForCausalLM("path/to/llama/model")

3. Compose Your Own Model

You can take individual kernels to compose your models.

from liger_kernel.transformers import LigerFusedLinearCrossEntropyLoss
import torch.nn as nn
import torch

model = nn.Linear(128, 256).cuda()

# fuses linear + cross entropy layers together and performs chunk-by-chunk computation to reduce memory
loss_fn = LigerFusedLinearCrossEntropyLoss()

input = torch.randn(4, 128, requires_grad=True, device="cuda")
target = torch.randint(256, (4, ), device="cuda")

loss = loss_fn(model.weight, input, target)
loss.backward()

High-level APIs

AutoModel

Patching

Low-level APIs

• Fused Linear kernels combine linear layers with losses, reducing memory usage by up to 80% - ideal for HBM-constrained workloads.
• Other kernels use fusion and in-place techniques for memory and performance optimization.

Model Kernels

Alignment Kernels

Distillation Kernels

Experimental Kernels

Contributing, Acknowledgements, and License

• Contributing Guidelines
• Acknowledgements
• License Information

Sponsorship and Collaboration

• Glows.ai: Sponsoring NVIDIA GPUs for our open source developers.
• AMD: Providing AMD GPUs for our AMD CI.
• Intel: Providing Intel GPUs for our Intel CI.
• Modal: Free 3000 credits from GPU MODE IRL for our NVIDIA CI.
• EmbeddedLLM: Making Liger Kernel run fast and stable on AMD.
• HuggingFace: Integrating Liger Kernel into Hugging Face Transformers and TRL.
• Lightning AI: Integrating Liger Kernel into Lightning Thunder.
• Axolotl: Integrating Liger Kernel into Axolotl.
• Llama-Factory: Integrating Liger Kernel into Llama-Factory.

CI status

Build

Contact

• For issues, create a Github ticket in this repository
• For open discussion, join our discord channel on GPUMode
• For formal collaboration, send an email to Yanning Chen([email protected]) and Zhipeng Wang([email protected])

Cite this work

Biblatex entry:

@inproceedings{
hsu2025ligerkernel,
title={Liger-Kernel: Efficient Triton Kernels for {LLM} Training},
author={Pin-Lun Hsu and Yun Dai and Vignesh Kothapalli and Qingquan Song and Shao Tang and Siyu Zhu and Steven Shimizu and Shivam Sahni and Haowen Ning and Yanning Chen and Zhipeng Wang},
booktitle={Championing Open-source DEvelopment in ML Workshop @ ICML25},
year={2025},
url={https://openreview.net/forum?id=36SjAIT42G}
}

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