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[Refactor] Quantization Module Refactor (#5738)

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### Summary

This PR refactors the `vllm_ascend/quantization` module to improve code
organization, maintainability, and extensibility. The refactoring
introduces a clear separation of concerns with a registry-based scheme
discovery pattern, abstract base classes for quantization schemes, and
dedicated wrapper classes.

### Key Changes

#### 1. **Modular Directory Structure**

| Before | After |
|--------|-------|
| Flat file structure with mixed responsibilities | Organized into
`methods/` subpackage for schemes |
| Single `quant_config.py` (600+ lines) | Separate config files:
`modelslim_config.py`, `compressed_tensors_config.py` |
| `utils.py` with scheme lookup logic | `methods/registry.py` with
decorator-based registration |

#### 2. **Registry-Based Scheme Discovery**

Replaced hardcoded `ASCEND_QUANTIZATION_METHOD_MAP` dictionary with a
decorator-based registry pattern:

```python
# Before: Manual dictionary mapping
ASCEND_QUANTIZATION_METHOD_MAP = {
    "W8A8_DYNAMIC": {"linear": AscendW8A8DynamicLinearMethod, ...},
    ...
}

# After: Decorator-based registration
@register_scheme("W8A8_DYNAMIC", "linear")
class AscendW8A8DynamicLinearMethod(AscendLinearScheme):
    ...
```

#### 3. **Abstract Base Classes**

Introduced three abstract base classes in `methods/base.py`:
- `AscendLinearScheme` - Base for linear layer quantization
- `AscendMoEScheme` - Base for MoE layer quantization  
- `AscendAttentionScheme` - Base for attention layer quantization

#### 4. **Separated Config and Wrapper Classes**

- **Config classes** (`AscendModelSlimConfig`,
`AscendCompressedTensorsConfig`): Handle config parsing and scheme
selection
- **Wrapper classes** (`AscendLinearMethod`, `AscendFusedMoEMethod`,
etc.): Implement vLLM interfaces and delegate to schemes

#### 5. **Cleaner Public API**

```python
# New clean module interface
from vllm_ascend.quantization import (
    AscendModelSlimConfig,
    AscendCompressedTensorsConfig,
)
from vllm_ascend.quantization.methods import get_scheme_class
```

### Architecture Diagram

```mermaid
classDiagram
    direction TB
    
    class QuantizationConfig {
        <<vLLM Interface>>
        +get_quant_method()
    }
    
    class AscendModelSlimConfig {
        +quant_description
        +get_quant_method()
        -create_scheme_for_layer()
    }
    
    class AscendCompressedTensorsConfig {
        +target_scheme_map
        +get_quant_method()
        -_get_scheme_from_parts()
    }
    
    class AscendLinearMethod {
        <<Wrapper>>
        +quant_method: AscendLinearScheme
        +create_weights()
        +apply()
    }
    
    class AscendFusedMoEMethod {
        <<Wrapper>>
        +quant_method: AscendMoEScheme
        +create_weights()
        +apply()
    }
    
    class AscendLinearScheme {
        <<Abstract>>
        +get_weight()*
        +apply()*
        +get_pertensor_param()
        +get_perchannel_param()
    }
    
    class AscendMoEScheme {
        <<Abstract>>
        +get_weight()*
        +get_dynamic_quant_param()*
        +apply()*
    }
    
    class W8A8DynamicLinear {
        +get_weight()
        +apply()
    }
    
    class W8A8DynamicMoE {
        +get_weight()
        +apply()
    }
    
    QuantizationConfig <|-- AscendModelSlimConfig
    QuantizationConfig <|-- AscendCompressedTensorsConfig
    
    AscendModelSlimConfig ..> AscendLinearMethod : creates
    AscendModelSlimConfig ..> AscendFusedMoEMethod : creates
    AscendCompressedTensorsConfig ..> AscendLinearMethod : creates
    AscendCompressedTensorsConfig ..> AscendFusedMoEMethod : creates
    
    AscendLinearMethod o-- AscendLinearScheme : delegates to
    AscendFusedMoEMethod o-- AscendMoEScheme : delegates to
    
    AscendLinearScheme <|-- W8A8DynamicLinear
    AscendMoEScheme <|-- W8A8DynamicMoE
```

### Scheme Registration Flow

```mermaid
sequenceDiagram
    participant Module as Scheme Module
    participant Registry as _SCHEME_REGISTRY
    participant Config as QuantConfig
    participant Wrapper as Wrapper Class
    
    Note over Module: At import time
    Module->>Registry: @register_scheme("W8A8_DYNAMIC", "linear")
    Registry->>Registry: Store (quant_type, layer_type) -> Class
    
    Note over Config: At runtime
    Config->>Config: Determine quant_type from description
    Config->>Registry: get_scheme_class(quant_type, layer_type)
    Registry-->>Config: Return scheme class
    Config->>Config: scheme = scheme_cls()
    Config->>Wrapper: Create wrapper with scheme
    Wrapper-->>Config: Return wrapper instance
```

### File Changes Summary

| Original Files | Refactored Files |
|----------------|------------------|
| `__init__.py` (empty) | `__init__.py` (exports public API) |
| `quant_config.py` | `modelslim_config.py` + `wrappers.py` |
| `compressed_tensors/` | `compressed_tensors_config.py` |
| `utils.py` | `methods/registry.py` |
| `w8a8_dynamic.py` | `methods/w8a8_dynamic.py` |
| `w8a8.py` | `methods/w8a8_static.py` |
| `w4a4_flatquant_dynamic.py` | `methods/w4a4_flatquant.py` |
| ... | `methods/base.py` (new) |

### Benefits

1. **Extensibility**: Adding new quantization schemes only requires
implementing the base class and adding `@register_scheme` decorator
2. **Maintainability**: Clear separation between config parsing, wrapper
logic, and scheme implementation
3. **Testability**: Abstract base classes enable easier unit testing and
mocking
4. **Discoverability**: Registry pattern makes it easy to list all
supported schemes
5. **Reduced Coupling**: Config classes no longer need to know about all
scheme implementations

___

- vLLM version: v0.13.0
- vLLM main:
2f4e6548ef

---------

Signed-off-by: SlightwindSec <slightwindsec@gmail.com>
This commit is contained in:
Cao Yi
2026-01-23 14:13:47 +08:00
committed by GitHub
parent 8378bc28b0
commit a69ef10c3a
36 changed files with 2044 additions and 1524 deletions
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23
docs/source/developer_guide/feature_guide/quantization.md
View File

@@ -10,7 +10,7 @@ The current process for registering and obtaining quantization methods in vLLM A
![get_quant_method](../../assets/quantization/get_quant_method.png)
vLLM Ascend registers a custom ascend quantization method. By configuring the `--quantization ascend` parameter (or `quantization="ascend"` for offline), the quantization feature is enabled. When constructing the `quant_config`, the registered `AscendQuantConfig` is initialized and `get_quant_method` is called to obtain the quantization method corresponding to each weight part, stored in the `quant_method` attribute.
vLLM Ascend registers a custom ascend quantization method. By configuring the `--quantization ascend` parameter (or `quantization="ascend"` for offline), the quantization feature is enabled. When constructing the `quant_config`, the registered `AscendModelSlimConfig` is initialized and `get_quant_method` is called to obtain the quantization method corresponding to each weight part, stored in the `quant_method` attribute.
Currently supported quantization methods include `AscendLinearMethod`, `AscendFusedMoEMethod`, `AscendEmbeddingMethod`, and their corresponding non-quantized methods:
@@ -51,18 +51,21 @@ Based on the above content, we present a brief description of the adaptation pro
### Quantization Algorithm Adaptation
- **Step 1: Algorithm Design**. Define the algorithm ID (e.g., `W4A8_DYNAMIC`), determine supported layers (linear, moe, attention), and design the quantization scheme (static/dynamic, pertensor/perchannel/pergroup).
- **Step 2: Registration**. Add the algorithm ID to `ASCEND_QUANTIZATION_METHOD_MAP` in `vllm_ascend/quantization/utils.py` and associate it with the corresponding method class.
- **Step 2: Registration**. Use the `@register_scheme` decorator in `vllm_ascend/quantization/methods/registry.py` to register your quantization scheme class.
```python
ASCEND_QUANTIZATION_METHOD_MAP: Dict[str, Dict[str, Type[Any]]] = {
"W4A8_DYNAMIC": {
"linear": AscendW4A8DynamicLinearMethod,
"moe": AscendW4A8DynamicFusedMoEMethod,
},
}
from vllm_ascend.quantization.methods import register_scheme, AscendLinearScheme
@register_scheme("W4A8_DYNAMIC", "linear")
class AscendW4A8DynamicLinearMethod(AscendLinearScheme):
...
@register_scheme("W4A8_DYNAMIC", "moe")
class AscendW4A8DynamicFusedMoEMethod(AscendMoEScheme):
...
```
- **Step 3: Implementation**. Create an algorithm implementation file, such as `vllm_ascend/quantization/w4a8_dynamic.py`, and implement the method class and logic.
- **Step 3: Implementation**. Create an algorithm implementation file, such as `vllm_ascend/quantization/methods/w4a8.py`, and implement the method class and logic.
- **Step 4: Testing**. Use your algorithm to generate quantization configurations and verify correctness and performance on target models and hardware.
### Quantized Model Adaptation
@@ -70,7 +73,7 @@ ASCEND_QUANTIZATION_METHOD_MAP: Dict[str, Dict[str, Type[Any]]] = {
Adapting a new quantized model requires ensuring the following three points:
- The original model has been successfully adapted in `vLLM Ascend`.
- **Fused Module Mapping**: Add the model's `model_type` to `packed_modules_model_mapping` in `vllm_ascend/quantization/quant_config.py` (e.g., `qkv_proj`, `gate_up_proj`, `experts`) to ensure sharding consistency and correct loading.
- **Fused Module Mapping**: Add the model's `model_type` to `packed_modules_model_mapping` in `vllm_ascend/quantization/modelslim_config.py` (e.g., `qkv_proj`, `gate_up_proj`, `experts`) to ensure sharding consistency and correct loading.
```python
packed_modules_model_mapping = {