base.py

import os
import gc
import json
import torch
import torch.nn as nn
from tqdm import tqdm
from typing import List, Union
from safetensors.torch import save_file
from awq.modules.act import ScaledActivation
from huggingface_hub import snapshot_download
from awq.quantize.quantizer import AwqQuantizer
from awq.utils.utils import simple_dispatch_model
from transformers.modeling_utils import shard_checkpoint
from awq.modules.linear import WQLinear_GEMM, WQLinear_GEMV
from awq.utils.module import get_named_linears, set_op_by_name
from transformers import AutoModelForCausalLM, AutoConfig, PreTrainedModel
from accelerate import init_empty_weights, load_checkpoint_in_model, infer_auto_device_map

class BaseAWQForCausalLM(nn.Module):
    def __init__(self, model, model_type, is_quantized, quant_config):
        super().__init__()
        self.model:PreTrainedModel = model
        self.model_type:str = model_type
        self.is_quantized:bool = is_quantized
        self.search_result = None
        self.quant_config:dict = quant_config
    
    def to(self, device: str):
        return self.model.to(device)
    
    def forward(self, *args, **kwargs):
        return self.model(*args, **kwargs)
    
    def generate(self, *args, **kwargs):
        with torch.inference_mode():
            return self.model.generate(*args, **kwargs)

    @torch.no_grad()
    def quantize(self, tokenizer=None, quant_config={},
                       calib_data: Union[str, List[str]]="pileval", 
                       split="train", text_column="text", loss_objective='mse'):
        self.quant_config = quant_config
        quant_config["version"] = "GEMM" if 'version' not in quant_config.keys() else quant_config["version"]

        quantizer = AwqQuantizer(
            self, self.model, tokenizer, quant_config["w_bit"], quant_config["q_group_size"],
            quant_config["version"], calib_data, split, text_column, loss_objective
        )
        quantizer.quantize()
        self.is_quantized = True
    
    @staticmethod
    def fuse_layers(model, quant_config):
        pass

    def save_quantized(self, save_dir, safetensors=False, shard_size="10GB"):
        save_dir = save_dir[:-1] if save_dir[-1] == '/' else save_dir

        # Save model
        class EmptyModule(nn.Module):
            def __init__(self): super(EmptyModule, self).__init__()
            def forward(self, x): return x

        # Save model files with empty state dict
        self.model.save_pretrained(save_dir, state_dict=EmptyModule().state_dict())

        # Remove empty state dict
        os.remove(f'{save_dir}/pytorch_model.bin')

        # model_name has no extension, add it when saving state_dict
        model_name = 'model.safetensors' if safetensors else 'pytorch_model.bin'

        # shard checkpoint into chunks (10GB default)
        shards, index = shard_checkpoint(
            self.model.state_dict(), 
            max_shard_size=shard_size, 
            weights_name=model_name
        )

        for shard_file, shard in shards.items():
            if safetensors:
                # safetensors must be in the same memory, so we duplicate and use contiguous memory
                shard = {k: v.clone().contiguous() for k, v in shard.items()}
                save_file(shard, os.path.join(save_dir, shard_file), metadata={"format": "pt"})
            else:
                torch.save(shard, os.path.join(save_dir, shard_file))

        # save shard index
        if index is not None:
            with open(f'{save_dir}/{model_name}.index.json', 'w+') as file:
                file.write(json.dumps(index, indent=4))

        # Save config
        with open(f'{save_dir}/quant_config.json', 'w+') as file:
            file.write(json.dumps(self.quant_config, indent=4))
        
        
    @classmethod
    def from_pretrained(self, model_path, model_type, torch_dtype: torch.dtype = torch.float16, 
                        trust_remote_code=True, safetensors=False):
        return self.from_quantized(
            model_path, 
            model_type, 
            model_filename='', 
            max_new_tokens=None,
            device='balanced', 
            torch_dtype=torch_dtype, 
            trust_remote_code=trust_remote_code, 
            safetensors=safetensors,
            is_quantized=False
        )

    @classmethod
    def from_quantized(self, model_path, model_type, model_filename='', 
                             max_new_tokens=None, device='balanced', torch_dtype=torch.float16, 
                             trust_remote_code=True, safetensors=False, is_quantized=True, 
                             fuse_layers=False, version='GEMM'):
        # [STEP 1] Download model if path is not a directory
        if not os.path.isdir(model_path):
            ignore_patterns = ["*msgpack*", "*h5*"]
            if safetensors:
                ignore_patterns.extend(["*.pt*", "*.bin*"])
            else:
                ignore_patterns.append("*.safetensors*")
            
            model_path = snapshot_download(model_path, ignore_patterns=ignore_patterns)
        
        if model_filename != '':
            model_weights_path = model_path + f'/{model_filename}'
        else:
            model_weights_path = model_path

        # [STEP 2] Load config and set sequence length
        # TODO: Create BaseAWQConfig class
        quant_config_path = f'{model_path}/quant_config.json'
        if os.path.exists(quant_config_path):
            with open(quant_config_path, 'r') as file:
                quant_config = json.loads(file.read())
            
            if "version" not in quant_config.keys():
                quant_config["version"] = version
        else:
            # Default config that works for most models
            quant_config = {"zero_point": True, "q_group_size": 128, "w_bit": 4, "version": version}
        
        # Load model config and set max generation length
        if max_new_tokens is None and hasattr(self, 'max_new_tokens_key'):
            config = AutoConfig.from_pretrained(model_path, trust_remote_code=trust_remote_code)
            config.max_new_tokens = getattr(config, self.max_new_tokens_key)
        else:
            max_new_tokens = 2048 if max_new_tokens is None else max_new_tokens
            config = AutoConfig.from_pretrained(model_path, trust_remote_code=trust_remote_code)
            config.max_new_tokens = max_new_tokens
        
        # [STEP 3] Load model
        with init_empty_weights():
            model = AutoModelForCausalLM.from_config(config=config, torch_dtype=torch_dtype, trust_remote_code=trust_remote_code)
        
        # Only need to replace layers if a model is AWQ quantized
        if is_quantized:
            # Prepare WQLinear layers, replace nn.Linear
            self._load_quantized_modules(self, model, quant_config, quant_config["version"])
        
        model.tie_weights()

        device_map = infer_auto_device_map(
            model,
            no_split_module_classes=[self.layer_type], 
            dtype=torch_dtype
        )

        # Load model weights
        if is_quantized:
            load_checkpoint_in_model(
                model,
                checkpoint=model_weights_path,
                device_map=device_map
            )
            
            model = simple_dispatch_model(model, device_map)
            
            if fuse_layers:
                self.fuse_layers(model, quant_config)

        else:
            # If not quantized, must load with AutoModelForCausalLM
            del model
            
            # Load model weights
            model = AutoModelForCausalLM.from_pretrained(
                model_weights_path, 
                device_map=device_map, 
                trust_remote_code=trust_remote_code, 
                offload_folder="offload", 
                offload_state_dict=True, 
                torch_dtype=torch_dtype, 
                use_safetensors=safetensors
            )
            model.eval()

        return self(model, model_type, is_quantized=is_quantized, quant_config=quant_config)

    def _load_quantized_modules(self, model, quant_config, version):
        # Real quantization of weights
        assert quant_config["zero_point"], "We only support zero_point quantization now."
        
        # Get blocks of model
        layers = self.get_model_layers(model)

        for i in tqdm(range(len(layers)), desc="Replacing layers..."):
            layer = layers[i]

            # Get every linear layer in a block
            named_linears = get_named_linears(layer)

            # Replace activation functions
            self._scale_activations(self, layer)

            # Replace nn.Linear with WQLinear
            for name, module in named_linears.items():
                if version == 'GEMM':
                    q_linear_module = WQLinear_GEMM
                elif version == 'GEMV':
                    q_linear_module = WQLinear_GEMV
                
                q_linear = q_linear_module.from_linear(
                    module,
                    quant_config['w_bit'],
                    quant_config['q_group_size'],
                    True
                )
                q_linear.to(next(layer.parameters()).device)
                set_op_by_name(layer, name, q_linear)
            
            torch.cuda.empty_cache()
            gc.collect()
    
    @staticmethod
    def _scale_activations(self, layer):
        scale_dict = self.get_act_for_scaling(layer)

        if scale_dict['is_scalable']:
            if not isinstance(scale_dict['scale_layer'], ScaledActivation):
                param = next(layer.parameters())

                # get activation scale
                scale_like = torch.ones(scale_dict['scale_shape'], dtype=param.dtype, device=param.device)

                # scale activation
                scaled_act = ScaledActivation(scale_dict['scale_layer'], scale_like)
                set_op_by_name(layer, scale_dict['scale_name'], scaled_act)