Fine-tuning and inference using multiple accelerators

Fine-tuning and inference using multiple accelerators#

Applies to Linux

2024-09-10

10 min read time

This section explains how to fine-tune a model on a multi-accelerator system. See Single-accelerator fine-tuning for a single accelerator or GPU setup.

Environment setup#

This section was tested using the following hardware and software environment.

Hardware	4 AMD Instinct MI300X accelerators
Software	ROCm 6.1, Ubuntu 22.04, PyTorch 2.1.2, Python 3.10
Libraries	`transformers` `datasets` `accelerate` `huggingface-hub` `peft` `trl` `scipy`
Base model	`meta-llama/Llama-2-7b-chat-hf`

Setting up the base implementation environment#

Install PyTorch for ROCm. Refer to the PyTorch installation guide. For consistent installation, it’s recommended to use official ROCm prebuilt Docker images with the framework pre-installed.
In the Docker container, check the availability of ROCM-capable accelerators using the following command.
```
rocm-smi --showproductname
```

Check that your accelerators are available to PyTorch.

import torch
print("Is a ROCm-GPU detected? ", torch.cuda.is_available())
print("How many ROCm-GPUs are detected? ", torch.cuda.device_count())

If successful, your output should look like this:

>>> print("Is a ROCm-GPU detected? ", torch.cuda.is_available())
Is a ROCm-GPU detected?  True
>>> print("How many ROCm-GPUs are detected? ", torch.cuda.device_count())
How many ROCm-GPUs are detected?  4

Tip

During training and inference, you can check the memory usage by running the rocm-smi command in your terminal. This tool helps you see shows which accelerators or GPUs are involved.

Hugging Face Accelerate for fine-tuning and inference#

Hugging Face Accelerate is a library that simplifies turning raw PyTorch code for a single accelerator into code for multiple accelerators for LLM fine-tuning and inference. It is integrated with Transformers allowing you to scale your PyTorch code while maintaining performance and flexibility.

As a brief example of model fine-tuning and inference using multiple GPUs, let’s use Transformers and load in the Llama 2 7B model.

Here, let’s reuse the code in Single-accelerator fine-tuning to load the base model and tokenizer.

Now, it’s important to adjust how you load the model. Add the device_map parameter to your base model configuration.

...
base_model_name = "meta-llama/Llama-2-7b-chat-hf"

# Load base model to GPU memory
base_model = AutoModelForCausalLM.from_pretrained(
        base_model_name,
        device_map = "auto",
        trust_remote_code = True)
...
# Run training
sft_trainer.train()

Note

You can let Accelerate handle the device map computation by setting device_map to one of the supported options ("auto", "balanced", "balanced_low_0", "sequential").

It’s recommended to set the device_map parameter to “auto” to allow Accelerate to automatically and efficiently allocate the model given the available resources (4 accelerators in this case).

When you have more GPU memory available than the model size, here is the difference between each device_map option:

"auto" and "balanced" evenly split the model on all available GPUs, making it possible for you to use a batch size greater than 1.
"balanced_low_0" evenly splits the model on all GPUs except the first one, and only puts on GPU 0 what does not fit on the others. This option is great when you need to use GPU 0 for some processing of the outputs, like when using the generate function for Transformers models.
"sequential" will fit what it can on GPU 0, then move on GPU 1 and so forth. Not all GPUs might be used.

After loading the model in this way, the model is fully ready to use the resources available to it.

torchtune for fine-tuning and inference#

torchtune is a PyTorch-native library for easy single and multi-accelerator or GPU model fine-tuning and inference with LLMs.

Install torchtune using pip.

# Install torchtune with PyTorch release 2.2.2+
pip install torchtune

# To confirm that the package is installed correctly
tune --help

The output should look like this:

usage: tune [-h] {download,ls,cp,run,validate} ...

Welcome to the TorchTune CLI!

options:
  -h, --help            show this help message and exit

subcommands:
  {download,ls,cp,run,validate}

torchtune recipes are designed around easily composable components and workable training loops, with minimal abstraction getting in the way of fine-tuning. Run tune ls to show built-in torchtune configuration recipes.

RECIPE                                   CONFIG
full_finetune_single_device              llama2/7B_full_low_memory
                                         llama3/8B_full_single_device
                                         mistral/7B_full_low_memory
full_finetune_distributed                llama2/7B_full
                                         llama2/13B_full
                                         llama3/8B_full
                                         mistral/7B_full
                                         gemma/2B_full
lora_finetune_single_device              llama2/7B_lora_single_device
                                         llama2/7B_qlora_single_device
                                         llama3/8B_lora_single_device
                                         llama3/8B_qlora_single_device
                                         llama2/13B_qlora_single_device
                                         mistral/7B_lora_single_device

The RECIPE column shows the easy-to-use and workable fine-tuning and inference recipes for popular fine-tuning techniques (such as LoRA). The CONFIG column lists the YAML configurations for easily configuring training, evaluation, quantization, or inference recipes.

The snippet shows the architecture of a model’s YAML configuration file:

# Model arguments
model:
  _component_: torchtune.models.llama2.lora_llama2_7b
  lora_attn_modules: ['q_proj', 'v_proj']
  apply_lora_to_mlp: False
  apply_lora_to_output: False
  lora_rank: 8
  lora_alpha: 16

tokenizer:
  _component_: torchtune.models.llama2.llama2_tokenizer
  path: /tmp/Llama-2-7b-hf/tokenizer.model

# Dataset and sampler
dataset:
  _component_: torchtune.datasets.alpaca_cleaned_dataset
  train_on_input: True

This configuration file defines the fine-tuning base model path, data set, hyper-parameters for optimizer and scheduler, and training data type. To download the base model for fine-tuning, run the following command:
```
tune download meta-llama/Llama-2-7b-hf --output-dir /tmp/Llama-2-7b-hf --hf-token
```
The output directory argument for --output-dir should map the model path specified in YAML config file.

To launch lora_finetune_distributed on four devices, run the following command:

tune run --nnodes 1 --nproc_per_node 4 lora_finetune_distributed --config llama2/7B_lora

If successful, you should something like the following output:

INFO:torchtune.utils.logging:FSDP is enabled. Instantiating Model on CPU for Rank 0 ...
INFO:torchtune.utils.logging:Model instantiation took 7.32 secs
INFO:torchtune.utils.logging:Memory Stats after model init:
{'peak_memory_active': 9.478172672, 'peak_memory_alloc': 8.953868288, 'peak_memory_reserved': 11.112808448}
INFO:torchtune.utils.logging:Optimizer and loss are initialized.
INFO:torchtune.utils.logging:Dataset and Sampler are initialized.
INFO:torchtune.utils.logging:Learning rate scheduler is initialized.
1|111|Loss: 1.5790324211120605:   7%|█                                          | 114/1618

Read more about inference frameworks in LLM inference frameworks.