SGLang

SGLang is a structured generation language designed for large language models (LLMs). It makes your interaction with LLMs faster and more controllable by co-designing the frontend language and the runtime system.

The core features of SGLang include:

• A Flexible Front-End Language: This allows for easy programming of LLM applications with multiple chained generation calls, advanced prompting techniques, control flow, multiple modalities, parallelism, and external interaction.
• A High-Performance Runtime with RadixAttention: This feature significantly accelerates the execution of complex LLM programs by automatic KV cache reuse across multiple calls. It also supports other common techniques like continuous batching and tensor parallelism.

Contents

• Install
• Quick Start
• Frontend: Structured Generation Langauge (SGLang)
• Backend: SGLang Runtime (SRT)
• Benchmark And Performance
• Roadmap
• Citation And Acknowledgment

Install

Method 1: With Pip

Method 2: From Source

git clone git@github.com:sgl-project/sglang.git
cd sglang

pip install --upgrade pip
pip install -e "python[all]"

Quick Start

The example below shows how to use sglang to answer a mulit-turn question.

Using OpenAI Models

from sglang import function, system, user, assistant, gen, set_default_backend, OpenAI

@function
def multi_turn_question(s, question_1, question_2):
    s += system("You are a helpful assistant.")
    s += user(question_1)
    s += assistant(gen("answer_1", max_tokens=256))
    s += user(question_2)
    s += assistant(gen("answer_2", max_tokens=256))

set_default_backend(OpenAI("gpt-3.5-turbo"))

state = multi_turn_question.run(
    question_1="What is the capital of the United States?",
    question_2="List two local attractions.",
)

for m in state.messages():
    print(m["role"], ":", m["content"])

Using Local Models

First, launch a server with

python -m sglang.launch_server --model-path meta-llama/Llama-2-7b-chat-hf --port 30000

Then, connect to the server and answer a multi-turn question.

from sglang import function, system, user, assistant, gen, set_default_backend, RuntimeEndpoint

@function
def multi_turn_question(s, question_1, question_2):
    s += system("You are a helpful assistant.")
    s += user(question_1)
    s += assistant(gen("answer_1", max_tokens=256))
    s += user(question_2)
    s += assistant(gen("answer_2", max_tokens=256))

set_default_backend(RuntimeEndpoint("http://localhost:30000"))

state = multi_turn_question.run(
    question_1="What is the capital of the United States?",
    question_2="List two local attractions.",
)

for m in state.messages():
    print(m["role"], ":", m["content"])

More Examples

You can find more examples at examples/quick_start.

Frontend: Structured Generation Langauge (SGLang)

Control Flow

Parallelism

Multi Modality

@sgl.function
def multi_turn_question(s, image_file, question):
    s += sgl.user(sgl.image(image_file) + question)
    s += sgl.assistant(sgl.gen("answer_1", max_tokens=256))

Batching

Streaming

Other Backends

Backend: SGLang Runtime (SRT)

The SGLang Runtime (SRT) is designed to work best with the SGLang frontend. However, it can also be used as a standalone API server. In this case, the RadixAttention can still greatly accelerate many use cases.

Usage

Launch a server

python -m sglang.launch_server --model-path meta-llama/Llama-2-7b-chat-hf --port 30000

Send a request

curl http://localhost:30000/v1/completions \
  -H "Content-Type: application/json" \
  -d '{
    "prompt": "Say this is a test",
    "max_tokens": 16,
    "temperature": 0
  }'

Additional Arguments

• Add --tp 2 to enable tensor parallelism.

python -m sglang.launch_server --model-path meta-llama/Llama-2-7b-chat-hf --port 30000 --tp 2

Supported Models

• Llama
• Mistral
• Mixtral
• LLaVA

Benchmark And Performance

Roadmap

• Function call
• Constrained decoding
• Quantization
• S-LoRA
• More models

Citation And Acknowledgment

@misc{zheng2023efficiently,
      title={Efficiently Programming Large Language Models using SGLang},
      author={Lianmin Zheng and Liangsheng Yin and Zhiqiang Xie and Jeff Huang and Chuyue Sun and Cody Hao Yu and Shiyi Cao and Christos Kozyrakis and Ion Stoica and Joseph E. Gonzalez and Clark Barrett and Ying Sheng},
      year={2023},
      eprint={2312.07104},
      archivePrefix={arXiv},
      primaryClass={cs.AI}
}

We learned from the design and reused some code of the following projects: Guidance, vLLM, LightLLM, FlashInfer, LMQL.