# Step3

## 论文
`
Step-3 is Large yet Affordable: Model-system Co-design for Cost-effective Decoding
`
- https://arxiv.org/abs/2507.19427

## 模型结构
Step3 是一个先进的多模态推理模型，基于混合专家架构构建，拥有 321B 总参数，单token激活38B参数。
它采用端到端设计，旨在最大限度地降低解码成本，同时在视觉语言推理领域提供顶级性能。
通过 Multi-Matrix Factorization Attention(MFA)和Attention-FFN Disaggregation (AFD)的协同设计，Step3 高端和低端加速器上均保持卓越的效率。
AFD的架构实现如图所示。
<div align=center>
    <img src="./figures/AFD_architecture.png"/>
</div>

## 算法原理

Step-3引入了两大优化设计:

- 在模型算法方面，引入了MFA(Multi-matrix Factorization Attention)算法，其计算密度设计更加均衡，相较于MHA, GQA, MLA实现更低的decode成本。
- 在系统设计方面，引入了Attention FFN分离架构(Attention-FFN Disaggregation, AFD), 并根据具体硬件配置相应并行策略。


## 环境配置

### Docker（方法一）
```
docker pull image.sourcefind.cn:5000/dcu/admin/base/custom:vllm-ubuntu22.04-dtk25.04.1-rc5-das1.6-py3.10-20250802-step3
# <your IMAGE ID>为以上拉取的docker的镜像ID替换
docker run -it --shm-size=1024G -v $PWD/Step3_pytorch:/home/Step3_pytorch -v /opt/hyhal:/opt/hyhal:ro --privileged=true --device=/dev/kfd --device=/dev/dri/ --group-add video --name step3 <your IMAGE ID> bash

```
### Dockerfile（方法二）
```
cd $PWD/Step3_pytorch/docker
docker build --no-cache -t step3:latest .
docker run --shm-size=1024G --name step3 -v /opt/hyhal:/opt/hyhal:ro --privileged=true --device=/dev/kfd --device=/dev/dri/ --group-add video -v $PWD/Step3_pytorch:/home/Step3_pytorch -it step3 bash

```

## 数据集
`无`

## 训练
`无`

## 推理

注意：运行该模型需要16x64(GB)显存。
### 多机多卡
启动ray集群
```
#head节点执行
ray start --head --node-ip-address=*.*.*.*（主节点ip） --port=*** --num-gpus=8 --num-cpus=**
```

```
其余节点执行
ray start --address='*.*.*.*:***' (*.*.*.*:主节点ip,***:port) --num-gpus=8 --num-cpus=**
```

vLLM Deployment(vllm官方暂不支持AFD，只支持非分离模式部署):

```
#head节点执行
#Tensor Parallelism

VLLM_USE_NN=0 VLLM_USE_FLASH_ATTN_PA=0 vllm serve /path/to/step3 \
    --reasoning-parser step3 \
    --enable-auto-tool-choice \
    --tool-call-parser step3 \
    --trust-remote-code \
    --max-num-batched-tokens 4096 \
    --distributed-executor-backend ray  \
    --dtype float16  \
    -tp 16 \
    --port $PORT_SERVING 

```
` 暂不支持attention data parallelism`

- Client Request Examples
```
from openai import OpenAI

# Set OpenAI's API key and API base to use vLLM's API server.
openai_api_key = "EMPTY"
openai_api_base = "http://localhost:8000/v1"

client = OpenAI(
    api_key=openai_api_key,
    base_url=openai_api_base,
)

chat_response = client.chat.completions.create(
    model="/path/to/step3",
    messages=[
        {"role": "system", "content": "You are a helpful assistant."},
        {
            "role": "user",
            "content": [
                {
                    "type": "image_url",
                    "image_url": {
                        "url": "https://xxxxx.png"
                    },
                },
                {"type": "text", "text": "Please describe the image."},
            ],
        },
    ],
)
print("Chat response:", chat_response)
```
- You can also upload base64-encoded local images:
```
import base64
from openai import OpenAI
# Set OpenAI's API key and API base to use vLLM's API server.
openai_api_key = "EMPTY"
openai_api_base = "http://localhost:8000/v1"
client = OpenAI(
    api_key=openai_api_key,
    base_url=openai_api_base,
)
image_path = "/path/to/local/image.png"
with open(image_path, "rb") as f:
    encoded_image = base64.b64encode(f.read())
encoded_image_text = encoded_image.decode("utf-8")
base64_step = f"data:image;base64,{encoded_image_text}"
chat_response = client.chat.completions.create(
    model="step3",
    messages=[
        {"role": "system", "content": "You are a helpful assistant."},
        {
            "role": "user",
            "content": [
                {
                    "type": "image_url",
                    "image_url": {
                        "url": base64_step
                    },
                },
                {"type": "text", "text": "Please describe the image."},
            ],
        },
    ],
)
print("Chat response:", chat_response)
```
- text only:
```
from openai import OpenAI

# Set OpenAI's API key and API base to use vLLM's API server.
openai_api_key = "EMPTY"
openai_api_base = "http://localhost:8000/v1"
client = OpenAI(
    api_key=openai_api_key,
    base_url=openai_api_base,
)

chat_response = client.chat.completions.create(
    model="/path/to/step3",  # 模型路径
    messages=[
        {"role": "system", "content": "You are a helpful assistant."},
        {"role": "user", "content": "The capital of France is"},
    ],
)
print("Chat response:", chat_response.choices[0].message.content)
```

## result
example1:
- text:Please describe the image.
- image:

<div align=center>
    <img src="./figures/bee.jpg"/>
</div>


- 输出结果:


<div align=center>
    <img src="./figures/result.png"/>
</div>

### 精度
`无`
## 应用场景
### 算法类别
`对话问答`
### 热点应用行业
`电商,教育,广媒`
## 预训练权重
huggingface权重下载地址为：

- [stepfun-ai/step3](https://huggingface.co/stepfun-ai/step3)

`注：建议加镜像源下载：export HF_ENDPOINT=https://hf-mirror.com`
## 源码仓库及问题反馈
- https://developer.sourcefind.cn/codes/modelzoo/step3_pytorch
## 参考资料
- https://github.com/stepfun-ai/Step3/tree/main