[Quantization][1/N] MoE support BNB-Inflight Quantization (#20061)

Signed-off-by: Jee Jee Li <pandaleefree@gmail.com>

tests/models/quantization/test_bitsandbytes.py

@@ -14,7 +14,7 @@ from transformers import BitsAndBytesConfig
 from tests.quantization.utils import is_quant_method_supported
 
 from ...utils import compare_two_settings, multi_gpu_test
-from ..utils import check_embeddings_close
+from ..utils import check_embeddings_close, check_logprobs_close
 
 models_4bit_to_test = [
     ("facebook/opt-125m", "quantize opt model inflight"),
@@ -26,6 +26,10 @@ models_4bit_to_embedding_test = [
     ("intfloat/e5-mistral-7b-instruct", "quantize embedding model inflight"),
 ]
 
+models_4bit_to_moe_test = [
+    ("allenai/OLMoE-1B-7B-0125-Instruct", "quantize moe model inflight"),
+]
+
 models_pre_qaunt_4bit_to_test = [
     ('PrunaAI/Einstein-v6.1-Llama3-8B-bnb-4bit-smashed',
      'read pre-quantized 4-bit FP4 model'),
@@ -115,6 +119,35 @@ def test_load_pp_4bit_bnb_model(model_name, description) -> None:
     compare_two_settings(model_name, common_args, pp_args)
 
 
+@pytest.mark.skipif(not is_quant_method_supported("bitsandbytes"),
+                    reason='bitsandbytes is not supported on this GPU type.')
+@pytest.mark.parametrize("model_name, description", models_4bit_to_moe_test)
+def test_4bit_bnb_moe_model(hf_runner, vllm_runner, example_prompts,
+                            model_name, description) -> None:
+
+    hf_model_kwargs = dict(quantization_config=BitsAndBytesConfig(
+        load_in_4bit=True,
+        bnb_4bit_quant_type="nf4",
+        bnb_4bit_use_double_quant=True,
+    ))
+    with vllm_runner(model_name,
+                     quantization='bitsandbytes',
+                     enforce_eager=False) as llm:
+        vllm_outputs = llm.generate_greedy_logprobs(example_prompts,
+                                                    max_tokens=32,
+                                                    num_logprobs=5)
+
+    with hf_runner(model_name, model_kwargs=hf_model_kwargs) as llm:
+        transformers_outputs = llm.generate_greedy_logprobs_limit(
+            example_prompts, max_tokens=32, num_logprobs=5)
+    check_logprobs_close(
+        outputs_0_lst=transformers_outputs,
+        outputs_1_lst=vllm_outputs,
+        name_0="transformers",
+        name_1="vllm",
+    )
+
+
 @pytest.mark.skipif(not is_quant_method_supported("bitsandbytes"),
                     reason='bitsandbytes is not supported on this GPU type.')
 @pytest.mark.parametrize("model_name, description",
@@ -182,7 +215,8 @@ def validate_generated_texts(hf_runner,
                              model_name,
                              pre_quant=False,
                              hf_model_kwargs=None,
-                             vllm_tp_size=1):
+                             vllm_tp_size=1,
+                             max_tokens=8):
 
     # NOTE: run vLLM first, as it requires a clean process
     # when using distributed inference
@@ -190,7 +224,8 @@ def validate_generated_texts(hf_runner,
                      quantization=None if pre_quant else 'bitsandbytes',
                      tensor_parallel_size=vllm_tp_size,
                      enforce_eager=False) as llm:
-        vllm_outputs = llm.generate_greedy(prompts, 8)
+
+        vllm_outputs = llm.generate_greedy(prompts, max_tokens)
         vllm_logs = log_generated_texts(prompts, vllm_outputs, "VllmRunner")
 
     # Clean up the GPU memory for the next test
@@ -202,19 +237,17 @@ def validate_generated_texts(hf_runner,
 
     # Run with HF runner
     with hf_runner(model_name, model_kwargs=hf_model_kwargs) as llm:
-        hf_outputs = llm.generate_greedy(prompts, 8)
+        hf_outputs = llm.generate_greedy(prompts, max_tokens)
         hf_logs = log_generated_texts(prompts, hf_outputs, "HfRunner")
 
     # Clean up the GPU memory for the next test
     gc.collect()
     torch.cuda.empty_cache()
-
     # Compare the generated strings
     for hf_log, vllm_log in zip(hf_logs, vllm_logs):
         hf_str = hf_log["generated_text"]
         vllm_str = vllm_log["generated_text"]
         prompt = hf_log["prompt"]
-
         assert hf_str == vllm_str, (f"Model: {model_name}"
                                     f"Mismatch between HF and vLLM outputs:\n"
                                     f"Prompt: {prompt}\n"

vllm/model_executor/layers/fused_moe/layer.py

@@ -883,14 +883,21 @@ class FusedMoE(torch.nn.Module):
                            expert_data=expert_data,
                            tp_rank=tp_rank)
 
-    def _load_w13(self, expert_data: torch.Tensor, shard_dim: int,
-                  shard_id: str, loaded_weight: torch.Tensor, tp_rank: int):
+    def _load_w13(self,
+                  expert_data: torch.Tensor,
+                  shard_dim: int,
+                  shard_id: str,
+                  loaded_weight: torch.Tensor,
+                  tp_rank: int,
+                  load_full: bool = False):
 
         # Index the loaded weight for tp sharding.
         # gate_up_proj: "MergedColumnParallel", so tp sharding on output_dim
         shard_size = expert_data.shape[shard_dim] // 2
-        loaded_weight = loaded_weight.narrow(shard_dim, shard_size * tp_rank,
-                                             shard_size)
+        if not load_full:
+            loaded_weight = loaded_weight.narrow(shard_dim,
+                                                 shard_size * tp_rank,
+                                                 shard_size)
         # Narrow parameter and load.
         # w1, gate_proj: Load into first logical weight of w13.
         if shard_id == "w1":
@@ -998,6 +1005,27 @@ class FusedMoE(torch.nn.Module):
             param.data.copy_(loaded_weight)
             return True if return_success else None
 
+        # Case for BitsAndBytes
+        use_bitsandbytes_4bit = getattr(param, "use_bitsandbytes_4bit", False)
+        if use_bitsandbytes_4bit:
+            shard_dim = 0
+
+            expert_data = param.data[expert_id]
+            if shard_id == "w2":
+                expert_data.copy_(loaded_weight)
+            elif shard_id in ("w1", "w3"):
+                # BNB inflight quantization has already sharded the weights
+                full_load = True
+                self._load_w13(
+                    shard_id=shard_id,
+                    shard_dim=shard_dim,
+                    loaded_weight=loaded_weight,
+                    expert_data=expert_data,
+                    tp_rank=self.tp_rank,
+                    load_full=full_load,
+                )
+            return True if return_success else None
+
         # is_transposed: if the dim to shard the weight
         # should be flipped. Required by GPTQ, compressed-tensors
         # should be whatever dimension intermediate_size_per_partition is

vllm/model_executor/layers/quantization/bitsandbytes.py

 # SPDX-License-Identifier: Apache-2.0
 # SPDX-FileCopyrightText: Copyright contributors to the vLLM project
 
-from typing import Any, Optional
+from typing import Any, Callable, Optional, Union
 
 import torch
 
+from vllm.model_executor.layers.fused_moe import fused_experts
+from vllm.model_executor.layers.fused_moe.layer import (FusedMoE,
+                                                        FusedMoEMethodBase)
 from vllm.model_executor.layers.linear import (LinearBase, LinearMethodBase,
                                                UnquantizedLinearMethod,
                                                set_weight_attrs)
@@ -120,12 +123,15 @@ class BitsAndBytesConfig(QuantizationConfig):
             llm_int8_skip_modules=llm_int8_skip_modules,
             llm_int8_threshold=llm_int8_threshold)
 
-    def get_quant_method(self, layer: torch.nn.Module,
-                         prefix: str) -> Optional["LinearMethodBase"]:
+    def get_quant_method(
+        self, layer: torch.nn.Module, prefix: str
+    ) -> Optional[Union["LinearMethodBase", "BitsAndBytesMoEMethod"]]:
         if isinstance(layer, LinearBase):
             if is_layer_skipped_bnb(prefix, self.llm_int8_skip_modules):
                 return UnquantizedLinearMethod()
             return BitsAndBytesLinearMethod(self)
+        elif isinstance(layer, FusedMoE):
+            return BitsAndBytesMoEMethod(self)
         return None
 
 
@@ -146,6 +152,13 @@ def is_layer_skipped_bnb(prefix: str, llm_int8_skip_modules: list[str]):
     return substr_check or prefix_check
 
 
+def calculate_quant_ratio(dtype):
+    if dtype.is_floating_point:
+        return torch.finfo(dtype).bits // torch.iinfo(torch.uint8).bits
+    else:
+        return torch.iinfo(dtype).bits // torch.iinfo(torch.uint8).bits
+
+
 class BitsAndBytesLinearMethod(LinearMethodBase):
     """Linear method for BitsAndBytes.
 
@@ -173,12 +186,6 @@ class BitsAndBytesLinearMethod(LinearMethodBase):
                        **extra_weight_attrs):
         from bitsandbytes.nn import Int8Params
 
-        def calculate_quant_ratio(dtype):
-            if dtype.is_floating_point:
-                return torch.finfo(dtype).bits // torch.iinfo(torch.uint8).bits
-            else:
-                return torch.iinfo(dtype).bits // torch.iinfo(torch.uint8).bits
-
         def create_qweight_for_8bit():
             qweight = Int8Params(
                 data=torch.empty(sum(output_partition_sizes),
@@ -394,3 +401,210 @@ try:
 
 except AttributeError as error:
     raise error
+
+
+class BitsAndBytesMoEMethod(FusedMoEMethodBase):
+    """MoE method for BitsAndBytes.
+
+    Args:
+       quant_config: The BitsAndBytes quantization config.
+    """
+
+    def __init__(self, quant_config: BitsAndBytesConfig):
+        try:
+            import bitsandbytes
+            if bitsandbytes.__version__ < "0.45.3":
+                raise ImportError("bitsandbytes version is wrong. Please "
+                                  "install bitsandbytes>=0.45.3.")
+        except ImportError as err:
+            raise ImportError("Please install bitsandbytes>=0.45.3 via "
+                              "`pip install bitsandbytes>=0.45.3` to use "
+                              "bitsandbytes quantizer.") from err
+        self.topk_indices_dtype = None
+        self.quant_config = quant_config
+
+    def create_weights(
+        self,
+        layer: torch.nn.Module,
+        num_experts: int,
+        hidden_size: int,
+        intermediate_size_per_partition: int,
+        params_dtype: torch.dtype,
+        **extra_weight_attrs,
+    ):
+        if self.quant_config.load_in_8bit:
+            call_fun = self._create_weights_8bit
+        else:
+            call_fun = self._create_weights_4bit
+        call_fun(
+            layer,
+            num_experts,
+            hidden_size,
+            intermediate_size_per_partition,
+            params_dtype,
+            **extra_weight_attrs,
+        )
+
+    def apply(
+        self,
+        layer: torch.nn.Module,
+        x: torch.Tensor,
+        router_logits: torch.Tensor,
+        top_k: int,
+        renormalize: bool,
+        use_grouped_topk: bool = False,
+        topk_group: Optional[int] = None,
+        num_expert_group: Optional[int] = None,
+        global_num_experts: int = -1,
+        expert_map: Optional[torch.Tensor] = None,
+        custom_routing_function: Optional[Callable] = None,
+        scoring_func: str = "softmax",
+        e_score_correction_bias: Optional[torch.Tensor] = None,
+        apply_router_weight_on_input: bool = False,
+        activation: str = "silu",
+        enable_eplb: bool = False,
+        expert_load_view: Optional[torch.Tensor] = None,
+        logical_to_physical_map: Optional[torch.Tensor] = None,
+        logical_replica_count: Optional[torch.Tensor] = None,
+    ) -> torch.Tensor:
+
+        if enable_eplb:
+            raise NotImplementedError(
+                "EPLB not supported for `BitsAndBytesMoEMethod` yet.")
+        topk_weights, topk_ids = FusedMoE.select_experts(
+            hidden_states=x,
+            router_logits=router_logits,
+            use_grouped_topk=use_grouped_topk,
+            top_k=top_k,
+            renormalize=renormalize,
+            topk_group=topk_group,
+            num_expert_group=num_expert_group,
+            custom_routing_function=custom_routing_function,
+            scoring_func=scoring_func,
+            e_score_correction_bias=e_score_correction_bias,
+            indices_type=self.topk_indices_dtype)
+        if self.quant_config.load_in_8bit:
+            w13, w2 = self._apply_8bit_dequant(layer)
+        else:
+            w13, w2 = self._apply_4bit_dequnt(layer)
+        return fused_experts(
+            hidden_states=x,
+            w1=w13,
+            w2=w2,
+            topk_weights=topk_weights,
+            topk_ids=topk_ids,
+            inplace=True,
+            activation=activation,
+            apply_router_weight_on_input=apply_router_weight_on_input,
+            global_num_experts=global_num_experts,
+            expert_map=expert_map,
+        )
+
+    def _create_weights_4bit(
+        self,
+        layer: torch.nn.Module,
+        num_experts: int,
+        hidden_size: int,
+        intermediate_size_per_partition: int,
+        params_dtype: torch.dtype,
+        **extra_weight_attrs,
+    ):
+        quant_ratio = calculate_quant_ratio(params_dtype)
+        # Fused gate_up_proj (column parallel)
+        w13_total_size = (hidden_size * 2 *
+                          intermediate_size_per_partition) // quant_ratio
+        w13_qweight = torch.nn.Parameter(
+            torch.empty(
+                num_experts,
+                w13_total_size,
+                1,
+                dtype=torch.uint8,
+            ),
+            requires_grad=False,
+        )
+        layer.register_parameter("w13_weight", w13_qweight)
+        set_weight_attrs(w13_qweight, extra_weight_attrs)
+        set_weight_attrs(
+            w13_qweight,
+            {
+                "num_experts":
+                num_experts,
+                "input_dim":
+                hidden_size,
+                "output_dim":
+                2 * intermediate_size_per_partition,
+                "experts_shape": (
+                    num_experts,
+                    intermediate_size_per_partition * 2,
+                    hidden_size,
+                ),
+                "pack_factor":
+                quant_ratio,
+                "use_bitsandbytes_4bit":
+                True,
+            },
+        )
+        # down_proj (row parallel)
+        w2_total_size = (hidden_size *
+                         intermediate_size_per_partition) // quant_ratio
+        w2_qweight = torch.nn.Parameter(
+            torch.empty(
+                num_experts,
+                w2_total_size,
+                1,
+                dtype=torch.uint8,
+            ),
+            requires_grad=False,
+        )
+        set_weight_attrs(
+            w2_qweight,
+            {
+                "num_experts":
+                num_experts,
+                "input_dim":
+                intermediate_size_per_partition,
+                "output_dim":
+                hidden_size,
+                "experts_shape": (
+                    num_experts,
+                    hidden_size,
+                    intermediate_size_per_partition,
+                ),
+                "pack_factor":
+                quant_ratio,
+                "use_bitsandbytes_4bit":
+                True,
+            },
+        )
+        layer.register_parameter("w2_weight", w2_qweight)
+        set_weight_attrs(w2_qweight, extra_weight_attrs)
+
+    def _create_weights_8bit(
+        self,
+        layer: torch.nn.Module,
+        num_experts: int,
+        hidden_size: int,
+        intermediate_size_per_partition: int,
+        params_dtype: torch.dtype,
+        **extra_weight_attrs,
+    ):
+        raise NotImplementedError
+
+    def _apply_4bit_dequnt(
+            self, layer: torch.nn.Module) -> tuple[torch.Tensor, torch.Tensor]:
+        from bitsandbytes.functional import dequantize_4bit
+        w13 = dequantize_4bit(
+            layer.w13_weight.reshape(-1, 1),
+            layer.w13_weight.bnb_quant_state,
+        )
+        w2 = dequantize_4bit(
+            layer.w2_weight.reshape(-1, 1),
+            layer.w2_weight.bnb_quant_state,
+        )
+        w13 = w13.reshape(layer.w13_weight.experts_shape)
+        w2 = w2.reshape(layer.w2_weight.experts_shape)
+        return w13, w2
+
+    def _apply_8bit_dequant(
+            self, layer: torch.nn.Module) -> tuple[torch.Tensor, torch.Tensor]:
+        raise NotImplementedError

vllm/model_executor/model_loader/bitsandbytes_loader.py

@@ -20,6 +20,7 @@ from vllm.distributed import (get_tensor_model_parallel_rank,
                               get_tensor_model_parallel_world_size)
 # yapf: enable
 from vllm.logger import init_logger
+from vllm.model_executor.layers.fused_moe import FusedMoE
 from vllm.model_executor.layers.linear import (LinearBase,
                                                MergedColumnParallelLinear,
                                                QKVParallelLinear,
@@ -411,9 +412,33 @@ class BitsAndBytesModelLoader(BaseModelLoader):
                 # in case model has a mixture of disk-merged and disk-split
                 # weights with same last name.
                 self.target_modules.append(name)
+            elif (isinstance(module, FusedMoE)
+                  and hasattr(module.quant_method, "quant_config")):
+                if not hasattr(model, "get_expert_mapping"):
+                    raise AttributeError(
+                        f"MoE Model {type(model).__name__} does not support "
+                        "BitsAndBytes quantization yet. Ensure this model has "
+                        "'get_expert_mapping' method.")
+                # TODO: support FusedMoE with prequant and 8bit.
+                if self.pre_quant:
+                    raise ValueError(
+                        "Prequant BitsAndBytes models with FusedMoE is not "
+                        "supported yet.")
+                if self.load_8bit:
+                    raise ValueError(
+                        "BitsAndBytes 8bit quantization with FusedMoE is not "
+                        "supported yet.")
+                # Get the corresponding weight name using module name and
+                # get_expert_mapping.
+                expert_mapping = model.get_expert_mapping()
+                for exp in expert_mapping:
+                    weight_name = exp[1]
+                    rep_name = name.replace("experts",
+                                            "") + weight_name.removesuffix(".")
+                    self.target_modules.append(rep_name)
 
         assert (self.target_modules
-                ), "vllm currently does not support BNB quantization for"
+                ), "vLLM currently does not support BNB quantization for"
         f" {type(model).__name__}"
 
     def _classify_module_sharding(self, model: nn.Module):
@@ -437,6 +462,14 @@ class BitsAndBytesModelLoader(BaseModelLoader):
             # dimension (dim=-1)
             elif isinstance(module, (RowParallelLinear, )):
                 self.column_sharded_weights_modules.append(name)
+            elif isinstance(module, FusedMoE):
+                expert_mapping = model.get_expert_mapping()
+                for exp in expert_mapping:
+                    if exp[-1] == "w2":
+                        weight_name = exp[1]
+                        rep_name = name.replace(
+                            "experts", "") + weight_name.removesuffix(".")
+                        self.column_sharded_weights_modules.append(rep_name)
 
     def _verify_model_compatibility(self, model: nn.Module,
                                     model_config: ModelConfig) -> None:
@@ -490,34 +523,132 @@ class BitsAndBytesModelLoader(BaseModelLoader):
         self._get_bnb_target_modules(model)
         self._classify_module_sharding(model)
 
-    def load_weights(self, model: nn.Module,
-                     model_config: ModelConfig) -> None:
+    def _dequantize_dq(self, quant_states: Any):
+        """
+        When BNB employs Double Quantization, we perform the dequantization of 
+        these constants during weight loading rather than at inference time, 
+        thereby avoiding this computational overhead during inference. This 
+        comes at the cost of increased memory usage.
+        """
+        from bitsandbytes.functional import QuantState, dequantize_blockwise
 
-        self._verify_model_compatibility(model, model_config)
-        self._initialize_loader_state(model, model_config)
+        def _dequantize_single_state(quant_state):
+            """Helper function to dequantize a single QuantState object."""
+            if not (isinstance(quant_state, QuantState)
+                    and quant_state.nested):
+                return
 
-        logger.info("Loading weights with BitsAndBytes quantization. "
-                    "May take a while ...")
-        qweight_iterator, quant_state_dict = (
-            self._get_quantized_weights_iterator(
-                model_config.model,
-                model_config.revision,
-            ))
-        weights_to_load = {name for name, _ in model.named_parameters()}
-        loaded_weights = model.load_weights(qweight_iterator)
-        # Some models may have weights loading tracker unimplemented.
-        if loaded_weights is not None:
-            weights_not_loaded = weights_to_load - loaded_weights
-            if weights_not_loaded:
-                raise ValueError("Following weights were not initialized from "
-                                 f"checkpoint: {weights_not_loaded}")
+            # Copied from: https://github.com/bitsandbytes-foundation/bitsandbytes/blob/0.45.3/bitsandbytes/functional.py#L1352-#L1356
+            absmax = dequantize_blockwise(quant_state.absmax,
+                                          quant_state.state2)
+            absmax += quant_state.offset
 
-        param_dict = dict(model.named_parameters())
+            # Ensure float32 dtype
+            if absmax.dtype != torch.float32:
+                absmax = absmax.float()
+
+            quant_state.absmax = absmax
+            quant_state.nested = False
+            quant_state.offset = None
+            quant_state.state2 = None
+
+        if isinstance(quant_states, dict):
+            for quant_state in quant_states.values():
+                _dequantize_single_state(quant_state)
+        else:
+            _dequantize_single_state(quant_states)
+        return quant_states
+
+    def _fuse_moe_quant_states(self, model: nn.Module,
+                               quant_states_dict: dict) -> dict:
+        """
+        
+        This function consolidates individual expert quantization states into
+        fused representations for w13 and w2.
+        """
+        from bitsandbytes.functional import QuantState
+
+        if not hasattr(model, "get_expert_mapping"):
+            return dict()
+
+        expert_mapping = model.get_expert_mapping()
+        expert_qs_dict = {}
+        for name, module in model.named_modules():
+            if not isinstance(module, FusedMoE):
+                continue
+            w1_states_lst = []
+            w2_states_lst = []
+            w3_states_lst = []
+            for exp in expert_mapping:
+                shard_id = exp[-1]
+                if shard_id not in ("w1", "w2", "w3"):
+                    raise ValueError(f"shard_id must be ['w1','w2','w3'] but "
+                                     f"got {shard_id}.")
+                layer_prefix = name.split("experts")[0]
+                weight_qual_name = layer_prefix + exp[1] + "weight"
+                quant_state = self._dequantize_dq(
+                    quant_states_dict[weight_qual_name])
+                if shard_id == "w1":
+                    w1_states_lst.append(quant_state)
+                elif shard_id == "w2":
+                    w2_states_lst.append(quant_state)
+                else:
+                    w3_states_lst.append(quant_state)
+                del quant_states_dict[weight_qual_name]
+            assert (len(w1_states_lst) == len(w2_states_lst) ==
+                    len(w3_states_lst))
+            w13_absmax_lst = []
+            w2_absmax_lst = []
+            w13_total_dim0 = 0
+            w2_total_dim0 = 0
+            for w1_qs, w2_qs, w3_qs in zip(w1_states_lst, w2_states_lst,
+                                           w3_states_lst):
+                assert w1_qs.shape == w3_qs.shape
+                assert w1_qs.blocksize == w2_qs.blocksize == w3_qs.blocksize
+                assert w1_qs.dtype == w2_qs.dtype == w3_qs.dtype
+                # w1 and w3 are interleaved in storage
+                w13_absmax_lst.append(w1_qs.absmax)
+                w13_absmax_lst.append(w3_qs.absmax)
+                w2_absmax_lst.append(w2_qs.absmax)
+                w13_total_dim0 += w1_qs.shape[0] + w3_qs.shape[0]
+                w2_total_dim0 += w2_qs.shape[0]
+
+            w13_absmax = torch.cat(w13_absmax_lst)
+            w2_absmax = torch.cat(w2_absmax_lst)
+            # Create fused quantization state for w13.
+            w13_qs = QuantState(
+                absmax=w13_absmax,
+                shape=(w13_total_dim0, w1_states_lst[0].shape[1]),
+                code=w1_states_lst[0].code,
+                blocksize=w1_states_lst[0].blocksize,
+                quant_type="nf4",
+                dtype=w1_states_lst[0].dtype,
+            )
+            # Create fused quantization state for w2.
+            w2_qs = QuantState(
+                absmax=w2_absmax,
+                shape=(w2_total_dim0, w2_states_lst[0].shape[1]),
+                code=w2_states_lst[0].code,
+                blocksize=w2_states_lst[0].blocksize,
+                quant_type="nf4",
+                dtype=w2_states_lst[0].dtype,
+            )
+            # The weight suffixes .w13_weight and .w2_weight are consistent
+            # with the param in BitsAndBytesMoEMethod.
+            w13_weight_name = name + ".w13_weight"
+            w2_weight_name = name + ".w2_weight"
+            expert_qs_dict[w13_weight_name] = w13_qs
+            expert_qs_dict[w2_weight_name] = w2_qs
+        return expert_qs_dict
+
+    def _stack_quantization_states(
+            self, model: nn.Module,
+            quant_state_dict: dict) -> dict[str, dict[int, Any]]:
         stacked_quant_state_dict: dict[str, dict[int, Any]] = {}
         # TODO: Change this lazy import to normal import
         # after the checks are updated to run on a new version
         from vllm.model_executor.models.utils import is_pp_missing_parameter
-
+        param_dict = dict(model.named_parameters())
         for quant_param_name in quant_state_dict:
             if is_pp_missing_parameter(quant_param_name, model):
                 continue
@@ -558,14 +689,20 @@ class BitsAndBytesModelLoader(BaseModelLoader):
 
             stacked_quant_state_dict[quant_param_name][shard_index] = (
                 quant_state_dict[non_stacked_param_name])
+        return stacked_quant_state_dict
 
+    def _bind_quant_states_to_params(self, model: nn.Module,
+                                     stacked_quant_state_dict: dict) -> None:
         # save quant_states and offsets as the attributes of the parameters
+        param_dict = dict(model.named_parameters())
         for param_name, param in param_dict.items():
             if param_name in stacked_quant_state_dict:
                 quant_states = stacked_quant_state_dict[param_name]
                 # Dequantize double quantized values during weight loading.
-                dequantize_dq(quant_states)
+                self._dequantize_dq(quant_states)
                 set_weight_attrs(param, {"bnb_quant_state": quant_states})
+                if not isinstance(quant_states, dict):
+                    continue
 
                 pack_ratio = getattr(param, "pack_factor", -1)
                 if pack_ratio == -1:
@@ -585,29 +722,40 @@ class BitsAndBytesModelLoader(BaseModelLoader):
                 if self.load_8bit:
                     set_weight_attrs(
                         param, {"matmul_state": [None] * len(quant_states)})
+
+    def load_weights(self, model: nn.Module,
+                     model_config: ModelConfig) -> None:
+
+        self._verify_model_compatibility(model, model_config)
+        self._initialize_loader_state(model, model_config)
+
+        logger.info("Loading weights with BitsAndBytes quantization. "
+                    "May take a while ...")
+        qweight_iterator, quant_state_dict = (
+            self._get_quantized_weights_iterator(
+                model_config.model,
+                model_config.revision,
+            ))
+        weights_to_load = {name for name, _ in model.named_parameters()}
+        loaded_weights = model.load_weights(qweight_iterator)
+        # Some models may have weights loading tracker unimplemented.
+        if loaded_weights is not None:
+            weights_not_loaded = weights_to_load - loaded_weights
+            if weights_not_loaded:
+                raise ValueError("Following weights were not initialized from "
+                                 f"checkpoint: {weights_not_loaded}")
+        expert_quant_state_dict = self._fuse_moe_quant_states(
+            model, quant_state_dict)
+
+        stacked_quant_state_dict = self._stack_quantization_states(
+            model, quant_state_dict)
+
+        stacked_quant_state_dict = {
+            **expert_quant_state_dict,
+            **stacked_quant_state_dict
+        }
+        self._bind_quant_states_to_params(model, stacked_quant_state_dict)
         torch.cuda.empty_cache()
 
     def download_model(self, model_config: ModelConfig) -> None:
         self._prepare_weights(model_config.model, model_config.revision)
-
-
-def dequantize_dq(quant_states: dict) -> None:
-    """
-    When BNB employs Double Quantization, we perform the dequantization of 
-    these constants during weight loading rather than at inference time, 
-    thereby avoiding this computational overhead during inference. This comes 
-    at the cost of increased memory usage.
-    """
-    from bitsandbytes.functional import QuantState, dequantize_blockwise
-    for _, quant_state in quant_states.items():
-        # Copied from: https://github.com/bitsandbytes-foundation/bitsandbytes/blob/0.45.3/bitsandbytes/functional.py#L1352-#L1356
-        if isinstance(quant_state, QuantState) and quant_state.nested:
-            absmax = dequantize_blockwise(quant_state.absmax,
-                                          quant_state.state2)
-            absmax += quant_state.offset
-            if absmax.dtype != torch.float32:
-                absmax = absmax.float()
-            quant_state.absmax = absmax
-            quant_state.nested = False
-            quant_state.offset = None
-            quant_state.state2 = None

vllm/model_executor/models/olmoe.py

@@ -330,6 +330,15 @@ class OlmoeModel(nn.Module):
         hidden_states, _ = self.norm(hidden_states, residual)
         return hidden_states
 
+    def get_expert_mapping(self) -> list[tuple[str, str, int, str]]:
+        # Params for weights, fp8 weight scales, fp8 activation scales
+        # (param_name, weight_name, expert_id, shard_id)
+        return FusedMoE.make_expert_params_mapping(
+            ckpt_gate_proj_name="gate_proj",
+            ckpt_down_proj_name="down_proj",
+            ckpt_up_proj_name="up_proj",
+            num_experts=self.config.num_experts)
+
     def load_weights(self, weights: Iterable[tuple[str,
                                                    torch.Tensor]]) -> set[str]:
         stacked_params_mapping = [
@@ -341,14 +350,6 @@ class OlmoeModel(nn.Module):
             ("gate_up_proj", "up_proj", 1),
         ]
 
-        # Params for weights, fp8 weight scales, fp8 activation scales
-        # (param_name, weight_name, expert_id, shard_id)
-        expert_params_mapping = FusedMoE.make_expert_params_mapping(
-            ckpt_gate_proj_name="gate_proj",
-            ckpt_down_proj_name="down_proj",
-            ckpt_up_proj_name="up_proj",
-            num_experts=self.config.num_experts)
-
         params_dict = dict(self.named_parameters())
         loaded_params: set[str] = set()
         for name, loaded_weight in weights:
@@ -379,7 +380,7 @@ class OlmoeModel(nn.Module):
                 weight_loader(param, loaded_weight, shard_id)
                 break
             else:
-                for mapping in expert_params_mapping:
+                for mapping in self.get_expert_mapping():
                     param_name, weight_name, expert_id, shard_id = mapping
                     if weight_name not in name:
                         continue
@@ -425,6 +426,17 @@ class OlmoeModel(nn.Module):
 
 
 class OlmoeForCausalLM(nn.Module, SupportsPP):
+    packed_modules_mapping = {
+        "qkv_proj": [
+            "q_proj",
+            "k_proj",
+            "v_proj",
+        ],
+        "gate_up_proj": [
+            "gate_proj",
+            "up_proj",
+        ],
+    }
 
     def __init__(self, *, vllm_config: VllmConfig, prefix: str = ""):
         super().__init__()
@@ -466,3 +478,6 @@ class OlmoeForCausalLM(nn.Module, SupportsPP):
                                                    torch.Tensor]]) -> set[str]:
         loader = AutoWeightsLoader(self)
         return loader.load_weights(weights)
+
+    def get_expert_mapping(self) -> list[tuple[str, str, int, str]]:
+        return self.model.get_expert_mapping()

vllm/model_executor/models/phimoe.py

@@ -516,6 +516,14 @@ class PhiMoEModel(nn.Module):
         hidden_states = self.norm(hidden_states)
         return hidden_states
 
+    def get_expert_mapping(self) -> list[tuple[str, str, int, str]]:
+        return FusedMoE.make_expert_params_mapping(
+            ckpt_gate_proj_name="w1",
+            ckpt_down_proj_name="w2",
+            ckpt_up_proj_name="w3",
+            num_experts=self.config.num_local_experts,
+        )
+
     def load_weights(self, weights: Iterable[tuple[str,
                                                    torch.Tensor]]) -> set[str]:
         stacked_params_mapping = [
@@ -672,3 +680,6 @@ class PhiMoEForCausalLM(nn.Module, SupportsLoRA, SupportsPP):
                                                    torch.Tensor]]) -> set[str]:
         loader = AutoWeightsLoader(self)
         return loader.load_weights(weights)
+
+    def get_expert_mapping(self) -> list[tuple[str, str, int, str]]:
+        return self.model.get_expert_mapping()

vllm/model_executor/models/qwen2_moe.py

@@ -391,6 +391,15 @@ class Qwen2MoeModel(nn.Module):
         hidden_states, _ = self.norm(hidden_states, residual)
         return hidden_states
 
+    def get_expert_mapping(self) -> list[tuple[str, str, int, str]]:
+        # Params for weights, fp8 weight scales, fp8 activation scales
+        # (param_name, weight_name, expert_id, shard_id)
+        return FusedMoE.make_expert_params_mapping(
+            ckpt_gate_proj_name="gate_proj",
+            ckpt_down_proj_name="down_proj",
+            ckpt_up_proj_name="up_proj",
+            num_experts=self.config.num_experts)
+
     def load_weights(self, weights: Iterable[tuple[str,
                                                    torch.Tensor]]) -> set[str]:
         stacked_params_mapping = [
@@ -402,14 +411,6 @@ class Qwen2MoeModel(nn.Module):
             ("gate_up_proj", "up_proj", 1),
         ]
 
-        # Params for weights, fp8 weight scales, fp8 activation scales
-        # (param_name, weight_name, expert_id, shard_id)
-        expert_params_mapping = FusedMoE.make_expert_params_mapping(
-            ckpt_gate_proj_name="gate_proj",
-            ckpt_down_proj_name="down_proj",
-            ckpt_up_proj_name="up_proj",
-            num_experts=self.config.num_experts)
-
         params_dict = dict(self.named_parameters())
         loaded_params: set[str] = set()
         for name, loaded_weight in weights:
@@ -441,11 +442,13 @@ class Qwen2MoeModel(nn.Module):
                 weight_loader(param, loaded_weight, shard_id)
                 break
             else:
-                for mapping in expert_params_mapping:
+                for mapping in self.get_expert_mapping():
                     param_name, weight_name, expert_id, shard_id = mapping
                     if weight_name not in name:
                         continue
                     name = name.replace(weight_name, param_name)
+                    if "layers.13.mlp.experts.w2_weight" in name:
+                        pass
                     # Skip layers on other devices.
                     if is_pp_missing_parameter(name, self):
                         continue
@@ -493,6 +496,17 @@ class Qwen2MoeModel(nn.Module):
 class Qwen2MoeForCausalLM(nn.Module, SupportsPP):
 
     fall_back_to_pt_during_load = False
+    packed_modules_mapping = {
+        "qkv_proj": [
+            "q_proj",
+            "k_proj",
+            "v_proj",
+        ],
+        "gate_up_proj": [
+            "gate_proj",
+            "up_proj",
+        ],
+    }
 
     def __init__(self, *, vllm_config: VllmConfig, prefix: str = ""):
         super().__init__()
@@ -538,3 +552,6 @@ class Qwen2MoeForCausalLM(nn.Module, SupportsPP):
                                                    torch.Tensor]]) -> set[str]:
         loader = AutoWeightsLoader(self)
         return loader.load_weights(weights)
+
+    def get_expert_mapping(self) -> list[tuple[str, str, int, str]]:
+        return self.model.get_expert_mapping()

vllm/model_executor/models/qwen3_moe.py

@@ -375,6 +375,15 @@ class Qwen3MoeModel(nn.Module):
         hidden_states, _ = self.norm(hidden_states, residual)
         return hidden_states
 
+    def get_expert_mapping(self) -> list[tuple[str, str, int, str]]:
+        # Params for weights, fp8 weight scales, fp8 activation scales
+        # (param_name, weight_name, expert_id, shard_id)
+        return FusedMoE.make_expert_params_mapping(
+            ckpt_gate_proj_name="gate_proj",
+            ckpt_down_proj_name="down_proj",
+            ckpt_up_proj_name="up_proj",
+            num_experts=self.config.num_experts)
+
     def load_weights(self, weights: Iterable[tuple[str,
                                                    torch.Tensor]]) -> set[str]:
         stacked_params_mapping = [
@@ -393,12 +402,7 @@ class Qwen3MoeModel(nn.Module):
 
         # Params for weights, fp8 weight scales, fp8 activation scales
         # (param_name, weight_name, expert_id, shard_id)
-        expert_params_mapping = FusedMoE.make_expert_params_mapping(
-            ckpt_gate_proj_name="gate_proj",
-            ckpt_down_proj_name="down_proj",
-            ckpt_up_proj_name="up_proj",
-            num_experts=self.config.num_experts)
-
+        expert_params_mapping = self.get_expert_mapping()
         params_dict = dict(self.named_parameters())
         loaded_params: set[str] = set()
         for name, loaded_weight in weights:
@@ -539,3 +543,6 @@ class Qwen3MoeForCausalLM(nn.Module, SupportsPP):
                                                    torch.Tensor]]) -> set[str]:
         loader = AutoWeightsLoader(self)
         return loader.load_weights(weights)
+
+    def get_expert_mapping(self) -> list[tuple[str, str, int, str]]:
+        return self.model.get_expert_mapping()