/TransformerEngine

A library for accelerating Transformer models on NVIDIA GPUs, including using 8-bit floating point (FP8) precision on Hopper and Ada GPUs, to provide better performance with lower memory utilization in both training and inference.

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Transformer Engine

Quickstart | Installation | User Guide | Examples | FP8 Convergence | Integrations | Release notes

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What is Transformer Engine?

Transformer Engine (TE) is a library for accelerating Transformer models on NVIDIA GPUs, including using 8-bit floating point (FP8) precision on Hopper GPUs, to provide better performance with lower memory utilization in both training and inference. TE provides a collection of highly optimized building blocks for popular Transformer architectures and an automatic mixed precision-like API that can be used seamlessly with your framework-specific code. TE also includes a framework agnostic C++ API that can be integrated with other deep learning libraries to enable FP8 support for Transformers.

As the number of parameters in Transformer models continues to grow, training and inference for architectures such as BERT, GPT and T5 become very memory and compute-intensive. Most deep learning frameworks train with FP32 by default. This is not essential, however, to achieve full accuracy for many deep learning models. Using mixed-precision training, which combines single-precision (FP32) with lower precision (e.g. FP16) format when training a model, results in significant speedups with minimal differences in accuracy as compared to FP32 training. With Hopper GPU architecture FP8 precision was introduced, which offers improved performance over FP16 with no degradation in accuracy. Although all major deep learning frameworks support FP16, FP8 support is not available natively in frameworks today.

TE addresses the problem of FP8 support by providing APIs that integrate with popular Large Language Model (LLM) libraries. It provides a Python API consisting of modules to easily build a Transformer layer as well as a framework-agnostic library in C++ including structs and kernels needed for FP8 support. Modules provided by TE internally maintain scaling factors and other values needed for FP8 training, greatly simplifying mixed precision training for users.

Highlights

  • Easy-to-use modules for building Transformer layers with FP8 support
  • Optimizations (e.g. fused kernels) for Transformer models
  • Support for FP8 on NVIDIA Hopper and NVIDIA Ada GPUs
  • Support for optimizations across all precisions (FP16, BF16) on NVIDIA Ampere GPU architecture generations and later

Examples

PyTorch

import torch
import transformer_engine.pytorch as te
from transformer_engine.common import recipe

# Set dimensions.
in_features = 768
out_features = 3072
hidden_size = 2048

# Initialize model and inputs.
model = te.Linear(in_features, out_features, bias=True)
inp = torch.randn(hidden_size, in_features, device="cuda")

# Create an FP8 recipe. Note: All input args are optional.
fp8_recipe = recipe.DelayedScaling(margin=0, fp8_format=recipe.Format.E4M3)

# Enable autocasting for the forward pass
with te.fp8_autocast(enabled=True, fp8_recipe=fp8_recipe):
    out = model(inp)

loss = out.sum()
loss.backward()

JAX

Flax

import flax
import jax
import jax.numpy as jnp
import transformer_engine.jax as te
import transformer_engine.jax.flax as te_flax
from transformer_engine.common import recipe

BATCH = 32
SEQLEN = 128
HIDDEN = 1024

# Initialize RNG and inputs.
rng = jax.random.PRNGKey(0)
init_rng, data_rng = jax.random.split(rng)
inp = jax.random.normal(data_rng, [BATCH, SEQLEN, HIDDEN], jnp.float32)

# Create an FP8 recipe. Note: All input args are optional.
fp8_recipe = recipe.DelayedScaling(margin=0, fp8_format=recipe.Format.HYBRID)

# Enable autocasting for the forward pass
with te.fp8_autocast(enabled=True, fp8_recipe=fp8_recipe):
    model = te_flax.DenseGeneral(features=HIDDEN)

    def loss_fn(params, other_vars, inp):
      out = model.apply({'params':params, **other_vars}, inp)
      return jnp.mean(out)

    # Initialize models.
    variables = model.init(init_rng, inp)
    other_variables, params = flax.core.pop(variables, 'params')

    # Construct the forward and backward function
    fwd_bwd_fn = jax.value_and_grad(loss_fn, argnums=(0, 1))

    for _ in range(10):
      loss, (param_grads, other_grads) = fwd_bwd_fn(params, other_variables, inp)

Installation

Pre-requisites

  • Linux x86_64
  • CUDA 12.0+ for Hopper and CUDA 12.1+ for Ada
  • NVIDIA Driver supporting CUDA 12.0 or later
  • cuDNN 8.1 or later
  • For fused attention, CUDA 12.1 or later, NVIDIA Driver supporting CUDA 12.1 or later, and cuDNN 8.9 or later.

Docker

The quickest way to get started with Transformer Engine is by using Docker images on NVIDIA GPU Cloud (NGC) Catalog. For example to use the NGC PyTorch container interactively,

docker run --gpus all -it --rm nvcr.io/nvidia/pytorch:23.10-py3

Where 23.10 is the container version. For example, 23.10 for the October 2023 release.

pip

To install the latest stable version of Transformer Engine,

pip install git+https://github.com/NVIDIA/TransformerEngine.git@stable

This will automatically detect if any supported deep learning frameworks are installed and build Transformer Engine support for them. To explicitly specify frameworks, set the environment variable NVTE_FRAMEWORK to a comma-separated list (e.g. NVTE_FRAMEWORK=jax,pytorch).

From source

See the installation guide.

Compiling with FlashAttention-2

Transformer Engine release v0.11.0 adds support for FlashAttention-2 in PyTorch for improved performance.

It is a known issue that FlashAttention-2 compilation is resource-intensive and requires a large amount of RAM (see bug), which may lead to out of memory errors during the installation of Transformer Engine. Please try setting MAX_JOBS=1 in the environment to circumvent the issue.

Note that NGC PyTorch 23.08+ containers include FlashAttention-2.

Breaking Changes

v1.7: Padding mask definition for PyTorch

In an effort to unify the definition and usage of the attention mask across all three frameworks in Transformer Engine, the padding mask has changed from True meaning inclusion of the corresponding position in attention to exclusion of that position in our PyTorch implementation. Since v1.7, all attention mask types follow the same definition where True means masking out the corresponding position and False means including that position in attention calculation.

An example of this change is,

# for a batch of 3 sequences where `a`s, `b`s and `c`s are the useful tokens
# and `0`s are the padding tokens,
[a, a, a, 0, 0,
 b, b, 0, 0, 0,
 c, c, c, c, 0]
# the padding mask for this batch before v1.7 is,
[ True,  True,  True, False, False,
  True,  True, False, False, False,
  True,  True,  True,  True, False]
# and for v1.7 onwards it should be,
[False, False, False,  True,  True,
 False, False,  True,  True,  True,
 False, False, False, False,  True]

FP8 Convergence

FP8 has been tested extensively across different model architectures and configurations and we found no significant difference between FP8 and BF16 training loss curves. FP8 has also been validated for accuracy on downstream LLM tasks (e.g. LAMBADA and WikiText). Below are examples of models tested for convergence across different frameworks.

Model Framework Source
T5-770M JAX/T5x https://github.com/NVIDIA/JAX-Toolbox/tree/main/rosetta/rosetta/projects/t5x#convergence-and-performance
MPT-1.3B Mosaic Composer https://www.mosaicml.com/blog/coreweave-nvidia-h100-part-1
GPT-5B JAX/Paxml https://github.com/NVIDIA/JAX-Toolbox/tree/main/rosetta/rosetta/projects/pax#h100-results
GPT-5B NeMo Framework Available on request
LLama2-7B Alibaba Pai https://mp.weixin.qq.com/s/NQT0uKXLbXyh5031zBdeBQ
T5-11B JAX/T5x Available on request
MPT-13B Mosaic Composer https://www.databricks.com/blog/turbocharged-training-optimizing-databricks-mosaic-ai-stack-fp8
GPT-22B NeMo Framework Available on request
LLama2-70B Alibaba Pai https://mp.weixin.qq.com/s/NQT0uKXLbXyh5031zBdeBQ
GPT-175B JAX/Paxml https://github.com/NVIDIA/JAX-Toolbox/tree/main/rosetta/rosetta/projects/pax#h100-results

Integrations

Transformer Engine has been integrated with popular LLM frameworks such as:

Contributing

We welcome contributions to Transformer Engine! To contribute to Transformer Engine and make pull requests, follow the guidelines outlined in the CONTRIBUTING.rst guide.

Papers

Videos