[Doc] add qwen3 w4a4 tutorial (#4076)

### What this PR does / why we need it?
v0.11.0rc1 will introduce w4a4 quantization feature, so add this
tutorial.

### Does this PR introduce _any_ user-facing change?

No


- vLLM version: v0.11.0
- vLLM main:
83f478bb19

Signed-off-by: 22dimensions <waitingwind@foxmail.com>

docs/source/tutorials/index.md

@@ -8,6 +8,7 @@ single_npu_qwen2.5_vl
 single_npu_qwen2_audio
 single_npu_qwen3_embedding
 single_npu_qwen3_quantization
+single_npu_qwen3_w4a4
 multi_npu_qwen3_next
 multi_npu
 multi_npu_moge

docs/source/tutorials/single_npu_qwen3_w4a4.md

@@ -0,0 +1,141 @@
+# Single-NPU (Qwen3 32B W4A4)
+
+## Introduction
+
+W4A4 Flat Quantization is for better model compression and inference efficiency on Ascend devices.
+And W4A4 is supported since `v0.11.0rc1`. For modelslim, W4A4 is supported since `tag_MindStudio_8.2.RC1.B120_002`.
+
+The following steps will show how to quantize Qwen3 32B to W4A4.
+
+## Environment Preparation
+
+### Run Docker Container
+
+```{code-block} bash
+   :substitutions:
+# Update the vllm-ascend image
+export IMAGE=m.daocloud.io/quay.io/ascend/vllm-ascend:|vllm_ascend_version|
+docker run --rm \
+--name vllm-ascend \
+--shm-size=1g \
+--device /dev/davinci0 \
+--device /dev/davinci_manager \
+--device /dev/devmm_svm \
+--device /dev/hisi_hdc \
+-v /usr/local/dcmi:/usr/local/dcmi \
+-v /usr/local/bin/npu-smi:/usr/local/bin/npu-smi \
+-v /usr/local/Ascend/driver/lib64/:/usr/local/Ascend/driver/lib64/ \
+-v /usr/local/Ascend/driver/version.info:/usr/local/Ascend/driver/version.info \
+-v /etc/ascend_install.info:/etc/ascend_install.info \
+-v /root/.cache:/root/.cache \
+-p 8000:8000 \
+-it $IMAGE bash
+```
+
+### Install modelslim and Convert Model
+
+:::{note}
+You can choose to convert the model yourself or use the quantized model we uploaded,
+see https://www.modelscope.cn/models/vllm-ascend/Qwen3-32B-W4A4
+:::
+
+```bash
+git clone -b tag_MindStudio_8.2.RC1.B120_002 https://gitcode.com/Ascend/msit
+cd msit/msmodelslim
+
+# Install by run this script
+bash install.sh
+pip install accelerate
+# transformers 4.51.0 is required for Qwen3 series model
+# see https://gitcode.com/Ascend/msit/blob/master/msmodelslim/example/Qwen/README.md#%E7%8E%AF%E5%A2%83%E9%85%8D%E7%BD%AE
+pip install transformers==4.51.0
+
+cd example/Qwen
+# Original weight path, Replace with your local model path
+MODEL_PATH=/home/models/Qwen3-32B
+# Path to save converted weight, Replace with your local path
+SAVE_PATH=/home/models/Qwen3-32B-w4a4
+
+python3 w4a4.py --model_path $MODEL_PATH \
+                --save_directory $SAVE_PATH \
+                --calib_file ../common/qwen_qwen3_cot_w4a4.json \
+                --trust_remote_code True \
+                --batch_size 1
+```
+
+### Verify the Quantized Model
+
+The converted model files look like:
+
+```bash
+.
+|-- config.json
+|-- configuration.json
+|-- generation_config.json
+|-- quant_model_description.json
+|-- quant_model_weight_w4a4_flatquant_dynamic-00001-of-00011.safetensors
+|-- quant_model_weight_w4a4_flatquant_dynamic-00002-of-00011.safetensors
+|-- quant_model_weight_w4a4_flatquant_dynamic-00003-of-00011.safetensors
+|-- quant_model_weight_w4a4_flatquant_dynamic-00004-of-00011.safetensors
+|-- quant_model_weight_w4a4_flatquant_dynamic-00005-of-00011.safetensors
+|-- quant_model_weight_w4a4_flatquant_dynamic-00006-of-00011.safetensors
+|-- quant_model_weight_w4a4_flatquant_dynamic-00007-of-00011.safetensors
+|-- quant_model_weight_w4a4_flatquant_dynamic-00008-of-00011.safetensors
+|-- quant_model_weight_w4a4_flatquant_dynamic-00009-of-00011.safetensors
+|-- quant_model_weight_w4a4_flatquant_dynamic-00010-of-00011.safetensors
+|-- quant_model_weight_w4a4_flatquant_dynamic-00011-of-00011.safetensors
+|-- quant_model_weight_w4a4_flatquant_dynamic.safetensors.index.json
+|-- tokenizer.json
+|-- tokenizer_config.json
+`-- vocab.json
+```
+
+## Deployment
+
+### Online Serving on Single NPU
+
+```bash
+vllm serve /home/models/Qwen3-32B-w4a4 --served-model-name "qwen3-32b-w4a4" --max-model-len 4096 --quantization ascend
+```
+
+Once your server is started, you can query the model with input prompts.
+
+```bash
+curl http://localhost:8000/v1/completions \
+    -H "Content-Type: application/json" \
+    -d '{
+        "model": "qwen3-32b-w4a4",
+        "prompt": "what is large language model?",
+        "max_tokens": "128",
+        "top_p": "0.95",
+        "top_k": "40",
+        "temperature": "0.0"
+    }'
+```
+
+### Offline Inference on Single NPU
+
+:::{note}
+To enable quantization for ascend, quantization method must be "ascend".
+:::
+
+```python
+
+from vllm import LLM, SamplingParams
+
+prompts = [
+    "Hello, my name is",
+    "The future of AI is",
+]
+sampling_params = SamplingParams(temperature=0.6, top_p=0.95, top_k=40)
+
+llm = LLM(model="/home/models/Qwen3-32B-w4a4",
+          max_model_len=4096,
+          quantization="ascend")
+
+outputs = llm.generate(prompts, sampling_params)
+for output in outputs:
+    prompt = output.prompt
+    generated_text = output.outputs[0].text
+    print(f"Prompt: {prompt!r}, Generated text: {generated_text!r}")
+```