pytorch llm generative_ai quantized android text-generation arxiv:2302.13971 license:llama2 region:us
---
library_name: pytorch
license: llama2
pipeline_tag: text-generation
tags:
- llm
- generative_ai
- quantized
- android

---

![](https://qaihub-public-assets.s3.us-west-2.amazonaws.com/qai-hub-models/models/llama_v2_7b_chat_quantized/web-assets/model_demo.png)

# Llama-v2-7B-Chat: Optimized for Mobile Deployment
## State-of-the-art large language model useful on a variety of language understanding and generation tasks

Llama 2 is a family of LLMs. The "Chat" at the end indicates that the model is optimized for chatbot-like dialogue. The model is quantized to w4a16(4-bit weights and 16-bit activations) and part of the model is quantized to w8a16(8-bit weights and 16-bit activations) making it suitable for on-device deployment. For Prompt and output length specified below, the time to first token is Llama-PromptProcessor-Quantized's latency and average time per addition token is Llama-TokenGenerator-KVCache-Quantized's latency.

This model is an implementation of Llama-v2-7B-Chat found [here](https://huggingface.co/meta-llama/Llama-2-7b-chat-hf).
This repository provides scripts to run Llama-v2-7B-Chat on Qualcomm® devices.
More details on model performance across various devices, can be found
[here](https://aihub.qualcomm.com/models/llama_v2_7b_chat_quantized).


### Model Details

- **Model Type:** Text generation
- **Model Stats:**
  - Number of parameters: 7B
  - Precision: w4a16 + w8a16 (few layers)
  - Model-1 (Prompt Processor): Llama-PromptProcessor-Quantized
  - Max context length: 1024
  - Prompt processor model size: 3.6 GB
  - Prompt processor input: 1024 tokens
  - Prompt processor output: 1024 output tokens + KVCache for token generator
  - Model-2 (Token Generator): Llama-TokenGenerator-KVCache-Quantized
  - Token generator model size: 3.6 GB
  - Token generator input: 1 input token + past KVCache
  - Token generator output: 1 output token + KVCache for next iteration
  - Decoding length: 1024 (1 output token + 1023 from KVCache)
  - Use: Initiate conversation with prompt-processor and then token generator for subsequent iterations.

## Deploying Llama 2 on-device

Large Language Model (LLM) such as [Llama 2](https://llama.meta.com/llama2/) has the following complexities to deploy on-device:
1. Model size is too large to fit in device memory for inference
2. Multi-Head Attention (MHA) has large activations leading to fallback from accelerators
3. High model load and inference time

We can tackle the above constraints with the following steps:
1. Quantize weights to reduce on-disk model size, e.g., int8 or int4 weights
2. Quantize activations to reduce inference time memory pressure
3. Graph transformations to reduce inference time memory pressure, e.g., Multi-Head to Split-Head Attention (MHA -> SHA)
4. Graph transformations to convert or decompose operations into more accelerator friendly operations e.g. Linear to Conv
5. For LLM with 7B or more parameters, above steps are still not good enough on mobile,
  hence we go one step further and split model into sub-parts.

Here, we divide the model into 4 parts in order to
1. Make model exportable with low memory usage
2. Avoid inference time out-of-memory errors

In order to export Llama 2, please ensure
1. Host machine has >40GB memory (RAM+swap-space)
2. If you don't have enough memory, export.py will dump instructions to increase swap space accordingly.

## Sample output prompts generated on-device
1. --prompt "what is gravity?" --max-output-tokens 30
~~~
-------- Response Summary --------
Prompt: what is gravity?
Response: Hello! I'm here to help you answer your question. Gravity is a fundamental force of nature that affects the behavior of objects with mass
~~~

2. --prompt "what is 2+3?" --max-output-tokens 30
~~~
-------- Response Summary --------
Prompt: what is 2+3?
Response: Of course! I'm happy to help! The answer to 2+3 is 5.
~~~

3. --prompt "could you please write code for fibonacci series in python?" --max-output-tokens 100
~~~
-------- Response Summary --------
Prompt: could you please write code for fibonacci series in python?
Response: Of course! Here is an example of how you could implement the Fibonacci sequence in Python:
```
def fibonacci(n):
    if n <= 1:
        return n
    else:
        return fibonacci(n-1) + fibonacci(n-2)
```
You can test the function by calling it with different values of `n`, like this:
```
print(fibonacci(5))
~~~



| Device | Chipset | Target Runtime | Inference Time (ms) | Peak Memory Range (MB) | Precision | Primary Compute Unit | Target Model
| ---|---|---|---|---|---|---|---|
| Samsung Galaxy S23 Ultra (Android 13) | Snapdragon® 8 Gen 2 | QNN Model Library | 90.268 ms | 64 - 4351 MB | UINT16 | NPU | Llama2-TokenGenerator-KVCache-Quantized 
| Samsung Galaxy S23 Ultra (Android 13) | Snapdragon® 8 Gen 2 | QNN Model Library | 1917.811 ms | 0 - 1028 MB | UINT16 | NPU | Llama2-PromptProcessor-Quantized 



## Installation

This model can be installed as a Python package via pip.

```bash
pip install "qai-hub-models[llama_v2_7b_chat_quantized]"
```



## Configure Qualcomm® AI Hub to run this model on a cloud-hosted device

Sign-in to [Qualcomm® AI Hub](https://app.aihub.qualcomm.com/) with your
Qualcomm® ID. Once signed in navigate to `Account -> Settings -> API Token`.

With this API token, you can configure your client to run models on the cloud
hosted devices.
```bash
qai-hub configure --api_token API_TOKEN
```
Navigate to [docs](https://app.aihub.qualcomm.com/docs/) for more information.



## Demo off target

The package contains a simple end-to-end demo that downloads pre-trained
weights and runs this model on a sample input.

```bash
python -m qai_hub_models.models.llama_v2_7b_chat_quantized.demo
```

The above demo runs a reference implementation of pre-processing, model
inference, and post processing.

**NOTE**: If you want running in a Jupyter Notebook or Google Colab like
environment, please add the following to your cell (instead of the above).
```
%run -m qai_hub_models.models.llama_v2_7b_chat_quantized.demo
```


### Run model on a cloud-hosted device

In addition to the demo, you can also run the model on a cloud-hosted Qualcomm®
device. This script does the following:
* Performance check on-device on a cloud-hosted device
* Downloads compiled assets that can be deployed on-device for Android.
* Accuracy check between PyTorch and on-device outputs.

```bash
python -m qai_hub_models.models.llama_v2_7b_chat_quantized.export
```

```
Profile Job summary of Llama2-TokenGenerator-KVCache-Quantized
--------------------------------------------------
Device: Snapdragon X Elite CRD (11)
Estimated Inference Time: 118.14 ms
Estimated Peak Memory Range: 64.97-64.97 MB
Compute Units: NPU (34842) | Total (34842)

Profile Job summary of Llama2-PromptProcessor-Quantized
--------------------------------------------------
Device: Snapdragon X Elite CRD (11)
Estimated Inference Time: 2302.57 ms
Estimated Peak Memory Range: 10.29-10.29 MB
Compute Units: NPU (31766) | Total (31766)


```





## Deploying compiled model to Android


The models can be deployed using multiple runtimes:
- TensorFlow Lite (`.tflite` export): [This
  tutorial](https://www.tensorflow.org/lite/android/quickstart) provides a
  guide to deploy the .tflite model in an Android application.


- QNN (`.so` export ): This [sample
  app](https://docs.qualcomm.com/bundle/publicresource/topics/80-63442-50/sample_app.html)
provides instructions on how to use the `.so` shared library  in an Android application.


## View on Qualcomm® AI Hub
Get more details on Llama-v2-7B-Chat's performance across various devices [here](https://aihub.qualcomm.com/models/llama_v2_7b_chat_quantized).
Explore all available models on [Qualcomm® AI Hub](https://aihub.qualcomm.com/)

## License
- The license for the original implementation of Llama-v2-7B-Chat can be found
  [here](https://github.com/facebookresearch/llama/blob/main/LICENSE).
- The license for the compiled assets for on-device deployment can be found [here](https://github.com/facebookresearch/llama/blob/main/LICENSE)

## References
* [LLaMA: Open and Efficient Foundation Language Models](https://arxiv.org/abs/2302.13971)
* [Source Model Implementation](https://huggingface.co/meta-llama/Llama-2-7b-chat-hf)

## Community
* Join [our AI Hub Slack community](https://qualcomm-ai-hub.slack.com/join/shared_invite/zt-2d5zsmas3-Sj0Q9TzslueCjS31eXG2UA#/shared-invite/email) to collaborate, post questions and learn more about on-device AI.
* For questions or feedback please [reach out to us](mailto:ai-hub-support@qti.qualcomm.com).


