refactor model loader [unreachable code]: initial refactor (#655)

python/sglang/srt/layers/linear.py

@@ -0,0 +1,869 @@
+# temporarily adapted from https://github.com/vllm-project/vllm/blob/e76466dde2bc9525d55165ceaa600d298c7bf773/vllm/model_executor/layers/linear.py
+# FIXME: refactor the linear abstraction
+from abc import abstractmethod
+from typing import Dict, List, Optional, Tuple
+
+import torch
+import torch.nn.functional as F
+from torch.nn.parameter import Parameter
+from vllm.distributed import (
+    divide,
+    get_tensor_model_parallel_rank,
+    get_tensor_model_parallel_world_size,
+    split_tensor_along_last_dim,
+    tensor_model_parallel_all_gather,
+    tensor_model_parallel_all_reduce,
+)
+from vllm.logger import init_logger
+from vllm.model_executor.layers.quantization.base_config import (
+    QuantizationConfig,
+    QuantizeMethodBase,
+)
+from vllm.model_executor.utils import set_weight_attrs
+
+logger = init_logger(__name__)
+
+
+def adjust_marlin_shard(param, shard_size, shard_offset):
+    marlin_tile_size = getattr(param, "marlin_tile_size", None)
+    if marlin_tile_size is None:
+        return shard_size, shard_offset
+
+    return shard_size * marlin_tile_size, shard_offset * marlin_tile_size
+
+
+def adjust_bitsandbytes_shard(
+    param: Parameter, qkv_offsets: Dict[str, Tuple[int, int]], loaded_shard_id: str
+) -> Tuple[int, int]:
+    """Adjust the quantization offsets and sizes for BitsAndBytes sharding."""
+
+    total, _ = qkv_offsets["total"]
+    orig_offset, orig_size = qkv_offsets[loaded_shard_id]
+
+    quantized_total = param.data.shape[0]
+    quantized_offset = orig_offset * quantized_total // total
+    quantized_size = orig_size * quantized_total // total
+
+    return quantized_size, quantized_offset
+
+
+def adjust_scalar_to_fused_array(param, loaded_weight, shard_id):
+    """For fused modules (QKV and MLP) we have an array of length
+    N that holds 1 scale for each "logical" matrix. So the param
+    is an array of length N. The loaded_weight corresponds to
+    one of the shards on disk. Here, we slice the param based on
+    the shard_id for loading.
+    """
+    qkv_idxs = {"q": 0, "k": 1, "v": 2}
+
+    if isinstance(shard_id, str):
+        shard_id = qkv_idxs[shard_id]
+    elif not isinstance(shard_id, int):
+        raise ValueError(f"Unknown Shard Id {shard_id}")
+
+    # AutoFP8 scales do not have a shape
+    # compressed-tensors scales do have a shape
+    if len(loaded_weight.shape) != 0:
+        assert loaded_weight.shape[0] == 1
+        loaded_weight = loaded_weight[0]
+
+    return param[shard_id], loaded_weight
+
+
+class LinearMethodBase(QuantizeMethodBase):
+    """Base class for different (maybe quantized) linear methods."""
+
+    @abstractmethod
+    def create_weights(
+        self,
+        layer: torch.nn.Module,
+        input_size_per_partition: int,
+        output_partition_sizes: List[int],
+        input_size: int,
+        output_size: int,
+        params_dtype: torch.dtype,
+        **extra_weight_attrs,
+    ):
+        """Create weights for a linear layer.
+           The weights will be set as attributes of the layer.
+
+        Args:
+            layer: The layer that is using the LinearMethodBase factory.
+            input_size_per_partition: Size of the weight input dim on rank X.
+            output_partition_sizes: Sizes of the output dim of each logical
+                weight on rank X. E.g., output_partition_sizes for QKVLinear
+                is a list contains the width of Wq, Wk, Wv on rank X.
+            input_size: Size of the input dim of the weight across all ranks.
+            output_size: Size of the output dim of the weight across all ranks.
+            params_dtype: Datatype of the parameters.
+        """
+        raise NotImplementedError
+
+    @abstractmethod
+    def apply(
+        self,
+        layer: torch.nn.Module,
+        x: torch.Tensor,
+        bias: Optional[torch.Tensor] = None,
+    ) -> torch.Tensor:
+        """Apply the weights in layer to the input tensor.
+        Expects create_weights to have been called before on the layer."""
+        raise NotImplementedError
+
+
+class UnquantizedLinearMethod(LinearMethodBase):
+    """Linear method without quantization.
+
+    Args:
+        separate_bias_add: If true, add bias separately after matrix
+                           multiplication.
+    """
+
+    def __init__(self, separate_bias_add: bool = False):
+        self.separate_bias_add = separate_bias_add
+
+    def create_weights(
+        self,
+        layer: torch.nn.Module,
+        input_size_per_partition: int,
+        output_partition_sizes: List[int],
+        input_size: int,
+        output_size: int,
+        params_dtype: torch.dtype,
+        **extra_weight_attrs,
+    ):
+        weight = Parameter(
+            torch.empty(
+                sum(output_partition_sizes),
+                input_size_per_partition,
+                dtype=params_dtype,
+            ),
+            requires_grad=False,
+        )
+        set_weight_attrs(weight, {"input_dim": 1, "output_dim": 0})
+        layer.register_parameter("weight", weight)
+        set_weight_attrs(weight, extra_weight_attrs)
+
+    def apply(
+        self,
+        layer: torch.nn.Module,
+        x: torch.Tensor,
+        bias: Optional[torch.Tensor] = None,
+    ) -> torch.Tensor:
+        weight = layer.weight
+        if self.separate_bias_add:
+            if bias is not None:
+                return F.linear(x, weight) + bias
+            return F.linear(x, weight)
+        return F.linear(x, weight, bias)
+
+
+class LinearBase(torch.nn.Module):
+    """Base linear layer.
+
+    Args:
+        input_size: input dimension of the linear layer.
+        output_size: output dimension of the linear layer.
+        bias: If true, add bias.
+        skip_bias_add: If true, skip adding bias but instead return it.
+        params_dtype: Data type for the parameters.
+        quant_config: Quantization configure.
+    """
+
+    def __init__(
+        self,
+        input_size: int,
+        output_size: int,
+        skip_bias_add: bool = False,
+        params_dtype: Optional[torch.dtype] = None,
+        quant_config: Optional[QuantizationConfig] = None,
+    ):
+        super().__init__()
+
+        # Keep input parameters
+        self.input_size = input_size
+        self.output_size = output_size
+        self.skip_bias_add = skip_bias_add
+        if params_dtype is None:
+            params_dtype = torch.get_default_dtype()
+        self.params_dtype = params_dtype
+        if quant_config is None:
+            self.quant_method: Optional[QuantizeMethodBase] = UnquantizedLinearMethod()
+        else:
+            self.quant_method = quant_config.get_quant_method(self)
+
+    def forward(self, x: torch.Tensor) -> torch.Tensor:
+        raise NotImplementedError
+
+
+class ReplicatedLinear(LinearBase):
+    """Replicated linear layer.
+
+    Args:
+        input_size: input dimension of the linear layer.
+        output_size: output dimension of the linear layer.
+        bias: If true, add bias.
+        skip_bias_add: If true, skip adding bias but instead return it.
+        params_dtype: Data type for the parameters.
+        quant_config: Quantization configure.
+    """
+
+    def __init__(
+        self,
+        input_size: int,
+        output_size: int,
+        bias: bool = True,
+        skip_bias_add: bool = False,
+        params_dtype: Optional[torch.dtype] = None,
+        quant_config: Optional[QuantizationConfig] = None,
+    ):
+        super().__init__(
+            input_size, output_size, skip_bias_add, params_dtype, quant_config
+        )
+
+        # All the linear layer supports quant method.
+        assert self.quant_method is not None
+        self.quant_method.create_weights(
+            self,
+            self.input_size,
+            [self.output_size],
+            self.input_size,
+            self.output_size,
+            self.params_dtype,
+        )
+
+        if bias:
+            self.bias = Parameter(
+                torch.empty(self.output_size, dtype=self.params_dtype)
+            )
+            set_weight_attrs(self.bias, {"output_dim": 0})
+        else:
+            self.register_parameter("bias", None)
+
+    def forward(self, x: torch.Tensor) -> torch.Tensor:
+        bias = self.bias if not self.skip_bias_add else None
+        assert self.quant_method is not None
+        output = self.quant_method.apply(self, x, bias)
+        output_bias = self.bias if self.skip_bias_add else None
+        return output, output_bias
+
+    def extra_repr(self) -> str:
+        s = f"in_features={self.input_size}"
+        s += f", output_features={self.output_size}"
+        s += f", bias={self.bias is not None}"
+        return s
+
+
+class ColumnParallelLinear(LinearBase):
+    """Linear layer with column parallelism.
+
+    The linear layer is defined as Y = XA + b. A is parallelized along
+    its second dimension as A = [A_1, ..., A_p].
+
+    Args:
+        input_size: first dimension of matrix A.
+        output_size: second dimension of matrix A.
+        bias: If true, add bias.
+        gather_output: If true, call all-gather on output and make Y available
+                       to all GPUs, otherwise, every GPU will have its output
+                       which is Y_i = XA_i
+        skip_bias_add: This was added to enable performance optimizations where
+                       bias can be fused with other element-wise operations. we
+                       skip adding bias but instead return it.
+        params_dtype: Data type for the parameters.
+        quant_config: Quantization configure.
+        output_sizes: list of output sizes packed into one output, like for QKV
+                       the list would be size 3.
+    """
+
+    def __init__(
+        self,
+        input_size: int,
+        output_size: int,
+        bias: bool = True,
+        gather_output: bool = False,
+        skip_bias_add: bool = False,
+        params_dtype: Optional[torch.dtype] = None,
+        quant_config: Optional[QuantizationConfig] = None,
+        output_sizes: Optional[List[int]] = None,
+    ):
+        super().__init__(
+            input_size, output_size, skip_bias_add, params_dtype, quant_config
+        )
+
+        self.gather_output = gather_output
+
+        # Divide the weight matrix along the last dimension.
+        tp_size = get_tensor_model_parallel_world_size()
+        assert self.quant_method is not None
+        self.output_size_per_partition = divide(self.output_size, tp_size)
+        self.output_partition_sizes = [self.output_size_per_partition]
+        # If QKV or MergedColumn, use output size of each partition.
+        if hasattr(self, "output_sizes"):
+            self.output_partition_sizes = [
+                divide(output_size, tp_size) for output_size in self.output_sizes
+            ]
+
+        if output_sizes is None:
+            output_sizes = [output_size]
+        self.quant_method.create_weights(
+            layer=self,
+            input_size_per_partition=self.input_size,
+            output_partition_sizes=self.output_partition_sizes,
+            input_size=self.input_size,
+            output_size=self.output_size,
+            params_dtype=self.params_dtype,
+            weight_loader=self.weight_loader,
+        )
+        if bias:
+            self.bias = Parameter(
+                torch.empty(self.output_size_per_partition, dtype=params_dtype)
+            )
+            set_weight_attrs(
+                self.bias,
+                {
+                    "output_dim": 0,
+                    "weight_loader": self.weight_loader,
+                },
+            )
+        else:
+            self.register_parameter("bias", None)
+
+    def weight_loader(self, param: Parameter, loaded_weight: torch.Tensor):
+        if param.data.dtype != loaded_weight.dtype:
+            param.data = torch.empty_like(
+                param.data, dtype=loaded_weight.dtype, device="cuda"
+            )
+
+        tp_rank = get_tensor_model_parallel_rank()
+        output_dim = getattr(param, "output_dim", None)
+        param_data = param.data
+        if output_dim is not None:
+            shard_size = param_data.shape[output_dim]
+            start_idx = tp_rank * shard_size
+            loaded_weight = loaded_weight.narrow(output_dim, start_idx, shard_size)
+
+        # Special case for loading scales off disk, which often do not
+        # have a shape (such as in the case of AutoFP8).
+        if len(loaded_weight.shape) == 0:
+            loaded_weight = loaded_weight.reshape(1)
+
+        assert param_data.shape == loaded_weight.shape
+        param_data.copy_(loaded_weight)
+
+    def forward(self, input_):
+        bias = self.bias if not self.skip_bias_add else None
+
+        # Matrix multiply.
+        assert self.quant_method is not None
+        output_parallel = self.quant_method.apply(self, input_, bias)
+        if self.gather_output:
+            # All-gather across the partitions.
+            output = tensor_model_parallel_all_gather(output_parallel)
+        else:
+            output = output_parallel
+        output_bias = self.bias if self.skip_bias_add else None
+        return output, output_bias
+
+    def extra_repr(self) -> str:
+        s = f"in_features={self.input_size}"
+        s += f", output_features={self.output_size_per_partition}"
+        s += f", bias={self.bias is not None}"
+        s += f", tp_size={get_tensor_model_parallel_world_size()}"
+        s += f", gather_output={self.gather_output}"
+        return s
+
+
+class MergedColumnParallelLinear(ColumnParallelLinear):
+    """Packed linear layers with column parallelism.
+
+    Similar to ColumnParallelLinear, but the weight matrix is concatenated
+    along the output dimension. When the weight matrix is loaded, the
+    different partitions are sharded separately.
+
+    Args:
+        input_size: input dimension of the linear layer.
+        output_sizes: list of output dimensions of the linear layer.
+        bias: If true, add bias.
+        gather_output: If true, call all-gather on output and make the output
+                       available to all GPUs, otherwise, every GPU will have
+                       its own output.
+        skip_bias_add: This was added to enable performance optimizations where
+                       bias can be fused with other element-wise operations. we
+                       skip adding bias but instead return it.
+        params_dtype: Data type for the parameters.
+        quant_config: Quantization configure.
+    """
+
+    def __init__(
+        self,
+        input_size: int,
+        output_sizes: List[int],
+        bias: bool = True,
+        gather_output: bool = False,
+        skip_bias_add: bool = False,
+        params_dtype: Optional[torch.dtype] = None,
+        quant_config: Optional[QuantizationConfig] = None,
+    ):
+        self.output_sizes = output_sizes
+        tp_size = get_tensor_model_parallel_world_size()
+        assert all(output_size % tp_size == 0 for output_size in output_sizes)
+        super().__init__(
+            input_size=input_size,
+            output_size=sum(output_sizes),
+            bias=bias,
+            gather_output=gather_output,
+            skip_bias_add=skip_bias_add,
+            params_dtype=params_dtype,
+            quant_config=quant_config,
+        )
+
+    def weight_loader(
+        self,
+        param: Parameter,
+        loaded_weight: torch.Tensor,
+        loaded_shard_id: Optional[int] = None,
+    ):
+        if param.data.dtype != loaded_weight.dtype:
+            param.data = torch.empty_like(
+                param.data, dtype=loaded_weight.dtype, device="cuda"
+            )
+
+        param_data = param.data
+        output_dim = getattr(param, "output_dim", None)
+        # Special case for AQLM codebooks.
+        is_metadata = getattr(param, "is_metadata", False)
+        # Special case for per-tensor scale to load scalar into fused array.
+        needs_scalar_to_array = getattr(param, "needs_scalar_to_array", False)
+
+        if loaded_shard_id is None:
+            # Loaded weight is already fused on disk (qkv/mlp).
+            if output_dim is None:
+                if needs_scalar_to_array is not None:
+                    param_data, loaded_weight = adjust_scalar_to_fused_array(
+                        param_data, loaded_weight, 0
+                    )
+
+                assert param_data.shape == loaded_weight.shape
+                param_data.copy_(loaded_weight)
+                return
+            current_shard_offset = 0
+            shard_offsets: List[Tuple[int, int, int]] = []
+            for i, output_size in enumerate(self.output_sizes):
+                shard_offsets.append((i, current_shard_offset, output_size))
+                current_shard_offset += output_size
+            packed_dim = getattr(param, "packed_dim", None)
+            for shard_id, shard_offset, shard_size in shard_offsets:
+                # Special case for Quantization.
+                # If quantized, we need to adjust the offset and size to account
+                # for the packing.
+                if packed_dim == output_dim:
+                    shard_size = shard_size // param.pack_factor
+                    shard_offset = shard_offset // param.pack_factor
+                    # Special case for Marlin.
+                    shard_size, shard_offset = adjust_marlin_shard(
+                        param, shard_size, shard_offset
+                    )
+
+                loaded_weight_shard = loaded_weight.narrow(
+                    output_dim, shard_offset, shard_size
+                )
+                self.weight_loader(param, loaded_weight_shard, shard_id)
+            return
+
+        assert loaded_shard_id < len(self.output_sizes)
+        tp_rank = get_tensor_model_parallel_rank()
+        tp_size = get_tensor_model_parallel_world_size()
+        if output_dim is not None:
+            shard_offset = sum(self.output_sizes[:loaded_shard_id]) // tp_size
+            shard_size = self.output_sizes[loaded_shard_id] // tp_size
+            # Special case for quantization.
+            # If quantized, we need to adjust the offset and size to account
+            # for the packing.
+            packed_dim = getattr(param, "packed_dim", None)
+            if packed_dim == output_dim:
+                shard_size = shard_size // param.pack_factor
+                shard_offset = shard_offset // param.pack_factor
+                # Special case for Marlin.
+                shard_size, shard_offset = adjust_marlin_shard(
+                    param, shard_size, shard_offset
+                )
+
+            use_bitsandbytes = getattr(param, "use_bitsandbytes", False)
+            if use_bitsandbytes:
+                shard_size = loaded_weight.shape[output_dim]
+                shard_offset = loaded_weight.shape[output_dim] * loaded_shard_id
+
+            param_data = param_data.narrow(output_dim, shard_offset, shard_size)
+            start_idx = tp_rank * shard_size
+            loaded_weight = loaded_weight.narrow(output_dim, start_idx, shard_size)
+        # Special case for AQLM codebooks.
+        elif is_metadata:
+            # metadata indicates fixed size concatenated along dim 0
+            shard_size = loaded_weight.shape[0]
+            shard_offset = loaded_shard_id * shard_size
+            param_data = param_data.narrow(0, shard_offset, shard_size)
+
+        # Special case for per-tensor scales in fused case.
+        elif needs_scalar_to_array:
+            param_data, loaded_weight = adjust_scalar_to_fused_array(
+                param_data, loaded_weight, loaded_shard_id
+            )
+
+        else:
+            ignore_warning = getattr(param, "ignore_warning", False)
+            if not ignore_warning:
+                logger.warning(
+                    "Loading a weight without `output_dim` attribute in "
+                    "MergedColumnParallelLinear, assume the weight is "
+                    "the same for all partitions."
+                )
+
+        assert param_data.shape == loaded_weight.shape
+        param_data.copy_(loaded_weight)
+
+
+class QKVParallelLinear(ColumnParallelLinear):
+    """Linear layers for the attention's QKV transformation.
+
+    Linear layers for the linear transformation of the query, key, and value
+    vectors in the attention layer. The weight matrix is concatenated along
+    the output dimension. The layer is parallelized along the head dimension.
+    When the number of key/value heads is smaller than the number of query
+    heads (e.g., multi-query/grouped-query attention), the key/value head may
+    be replicated while the query heads are partitioned.
+
+    Args:
+        hidden_size: input hidden state size of the transformer.
+        head_size: size of each attention head.
+        total_num_heads: total number of attention query heads.
+        total_num_kv_heads: total number of attention key/value heads. If
+                            None, assume total_num_kv_heads = total_num_heads.
+        bias: If true, add bias.
+        skip_bias_add: This was added to enable performance optimizations where
+                       bias can be fused with other element-wise operations. we
+                       skip adding bias but instead return it.
+        params_dtype: Data type for the parameters.
+        quant_config: Quantization configure.
+    """
+
+    def __init__(
+        self,
+        hidden_size: int,
+        head_size: int,
+        total_num_heads: int,
+        total_num_kv_heads: Optional[int] = None,
+        bias: bool = True,
+        skip_bias_add: bool = False,
+        params_dtype: Optional[torch.dtype] = None,
+        quant_config: Optional[QuantizationConfig] = None,
+    ):
+        self.hidden_size = hidden_size
+        self.head_size = head_size
+        self.total_num_heads = total_num_heads
+        if total_num_kv_heads is None:
+            total_num_kv_heads = total_num_heads
+        self.total_num_kv_heads = total_num_kv_heads
+        # Divide the weight matrix along the last dimension.
+        tp_size = get_tensor_model_parallel_world_size()
+        self.num_heads = divide(self.total_num_heads, tp_size)
+        if tp_size >= self.total_num_kv_heads:
+            self.num_kv_heads = 1
+            self.num_kv_head_replicas = divide(tp_size, self.total_num_kv_heads)
+        else:
+            self.num_kv_heads = divide(self.total_num_kv_heads, tp_size)
+            self.num_kv_head_replicas = 1
+        input_size = self.hidden_size
+        output_size = (
+            (self.num_heads + 2 * self.num_kv_heads) * tp_size * self.head_size
+        )
+        self.output_sizes = [
+            self.num_heads * self.head_size * tp_size,  # q_proj
+            self.num_kv_heads * self.head_size * tp_size,  # k_proj
+            self.num_kv_heads * self.head_size * tp_size,  # v_proj
+        ]
+
+        super().__init__(
+            input_size=input_size,
+            output_size=output_size,
+            bias=bias,
+            gather_output=False,
+            skip_bias_add=skip_bias_add,
+            params_dtype=params_dtype,
+            quant_config=quant_config,
+        )
+
+    def weight_loader(
+        self,
+        param: Parameter,
+        loaded_weight: torch.Tensor,
+        loaded_shard_id: Optional[str] = None,
+    ):
+        if param.data.dtype != loaded_weight.dtype:
+            param.data = torch.empty_like(
+                param.data, dtype=loaded_weight.dtype, device="cuda"
+            )
+
+        param_data = param.data
+        output_dim = getattr(param, "output_dim", None)
+        # Special case for AQLM codebooks.
+        is_metadata = getattr(param, "is_metadata", False)
+
+        # Special case for per-tensor scales in fused case.
+        needs_scalar_to_array = getattr(param, "needs_scalar_to_array", False)
+
+        if loaded_shard_id is None:
+            # Loaded weight is already fused on disk (qkv/mlp).
+            if output_dim is None:
+                if needs_scalar_to_array is not None:
+                    param_data, loaded_weight = adjust_scalar_to_fused_array(
+                        param_data, loaded_weight, 0
+                    )
+
+                assert param_data.shape == loaded_weight.shape
+                param_data.copy_(loaded_weight)
+                return
+            shard_offsets = [
+                # (shard_id, shard_offset, shard_size)
+                ("q", 0, self.total_num_heads * self.head_size),
+                (
+                    "k",
+                    self.total_num_heads * self.head_size,
+                    self.total_num_kv_heads * self.head_size,
+                ),
+                (
+                    "v",
+                    (self.total_num_heads + self.total_num_kv_heads) * self.head_size,
+                    self.total_num_kv_heads * self.head_size,
+                ),
+            ]
+            packed_dim = getattr(param, "packed_dim", None)
+            for shard_id, shard_offset, shard_size in shard_offsets:
+                # Special case for Quantized Weights.
+                # If quantized, we need to adjust the offset and size to account
+                # for the packing.
+                if packed_dim == output_dim:
+                    shard_size = shard_size // param.pack_factor
+                    shard_offset = shard_offset // param.pack_factor
+
+                    # Special case for Marlin.
+                    shard_size, shard_offset = adjust_marlin_shard(
+                        param, shard_size, shard_offset
+                    )
+
+                loaded_weight_shard = loaded_weight.narrow(
+                    output_dim, shard_offset, shard_size
+                )
+                self.weight_loader(param, loaded_weight_shard, shard_id)
+            return
+
+        tp_rank = get_tensor_model_parallel_rank()
+        assert loaded_shard_id in ["q", "k", "v"]
+
+        # If output dim is defined, use the default loading process.
+        if output_dim is not None:
+            if loaded_shard_id == "q":
+                shard_offset = 0
+                shard_size = self.num_heads * self.head_size
+            elif loaded_shard_id == "k":
+                shard_offset = self.num_heads * self.head_size
+                shard_size = self.num_kv_heads * self.head_size
+            elif loaded_shard_id == "v":
+                shard_offset = (self.num_heads + self.num_kv_heads) * self.head_size
+                shard_size = self.num_kv_heads * self.head_size
+            # Special case for Quantized Weights.
+            # If quantized, we need to adjust the offset and size to account
+            # for the packing.
+            packed_dim = getattr(param, "packed_dim", None)
+            if packed_dim == output_dim:
+                shard_size = shard_size // param.pack_factor
+                shard_offset = shard_offset // param.pack_factor
+
+                # Special case for Marlin.
+                shard_size, shard_offset = adjust_marlin_shard(
+                    param, shard_size, shard_offset
+                )
+
+            use_bitsandbytes = getattr(param, "use_bitsandbytes", False)
+            if use_bitsandbytes:
+                orig_qkv_offsets = {
+                    "q": (0, self.num_heads * self.head_size),
+                    "k": (
+                        self.num_heads * self.head_size,
+                        self.num_kv_heads * self.head_size,
+                    ),
+                    "v": (
+                        (self.num_heads + self.num_kv_heads) * self.head_size,
+                        self.num_kv_heads * self.head_size,
+                    ),
+                    "total": (
+                        (self.num_heads + 2 * self.num_kv_heads) * self.head_size,
+                        0,
+                    ),
+                }
+                shard_size, shard_offset = adjust_bitsandbytes_shard(
+                    param, orig_qkv_offsets, loaded_shard_id
+                )
+
+            param_data = param_data.narrow(output_dim, shard_offset, shard_size)
+            if loaded_shard_id == "q":
+                shard_id = tp_rank
+            else:
+                shard_id = tp_rank // self.num_kv_head_replicas
+            start_idx = shard_id * shard_size
+            loaded_weight = loaded_weight.narrow(output_dim, start_idx, shard_size)
+        # Special case for for AQLM codebooks.
+        elif is_metadata:
+            # metadata indicates fixed size concatenated along dim 0
+            shard_size = loaded_weight.shape[0]
+            shard_index = ["q", "k", "v"].index(loaded_shard_id)
+            param_data = param_data.narrow(0, shard_index * shard_size, shard_size)
+        # Special case for per-tensor scales in fused case.
+        elif needs_scalar_to_array:
+            param_data, loaded_weight = adjust_scalar_to_fused_array(
+                param_data, loaded_weight, loaded_shard_id
+            )
+        else:
+            ignore_warning = getattr(param, "ignore_warning", False)
+            if not ignore_warning:
+                logger.warning(
+                    "Loading a weight without `output_dim` attribute in "
+                    "QKVParallelLinear, assume the weight is the same "
+                    "for all partitions."
+                )
+
+        assert param_data.shape == loaded_weight.shape
+        param_data.copy_(loaded_weight)
+
+
+class RowParallelLinear(LinearBase):
+    """Linear layer with row parallelism.
+
+    The linear layer is defined as Y = XA + b. A is parallelized along
+    its first dimension and X along its second dimension as:
+               -   -
+              | A_1 |
+              | .   |
+          A = | .   |        X = [X_1, ..., X_p]
+              | .   |
+              | A_p |
+               -   -
+    Arguments:
+        input_size: first dimension of matrix A.
+        output_size: second dimension of matrix A.
+        bias: If true, add bias. Note that bias is not parallelized.
+        input_is_parallel: If true, we assume that the input is already
+                           split across the GPUs and we do not split
+                           again.
+        skip_bias_add: This was added to enable performance optimization where
+                       bias can be fused with other element-wise operations.
+                       We skip adding bias but instead return it.
+        params_dtype: Data type for the parameters.
+        quant_config: Quantization configure.
+    """
+
+    def __init__(
+        self,
+        input_size: int,
+        output_size: int,
+        bias: bool = True,
+        input_is_parallel: bool = True,
+        skip_bias_add: bool = False,
+        params_dtype: Optional[torch.dtype] = None,
+        reduce_results: bool = True,
+        quant_config: Optional[QuantizationConfig] = None,
+    ):
+        super().__init__(
+            input_size, output_size, skip_bias_add, params_dtype, quant_config
+        )
+
+        self.input_is_parallel = input_is_parallel
+        self.reduce_results = reduce_results
+
+        # Divide the weight matrix along the last dimension.
+        self.tp_size = get_tensor_model_parallel_world_size()
+        self.input_size_per_partition = divide(input_size, self.tp_size)
+        assert self.quant_method is not None
+        self.quant_method.create_weights(
+            layer=self,
+            input_size_per_partition=self.input_size_per_partition,
+            output_partition_sizes=[self.output_size],
+            input_size=self.input_size,
+            output_size=self.output_size,
+            params_dtype=self.params_dtype,
+            weight_loader=self.weight_loader,
+        )
+        if not reduce_results and (bias and not skip_bias_add):
+            raise ValueError(
+                "When not reduce the results, adding bias to the "
+                "results can lead to incorrect results"
+            )
+
+        if bias:
+            self.bias = Parameter(torch.empty(self.output_size, dtype=params_dtype))
+            set_weight_attrs(
+                self.bias,
+                {
+                    "output_dim": 0,
+                    "weight_loader": self.weight_loader,
+                },
+            )
+        else:
+            self.register_parameter("bias", None)
+
+    def weight_loader(self, param: Parameter, loaded_weight: torch.Tensor):
+        if param.data.dtype != loaded_weight.dtype:
+            param.data = torch.empty_like(
+                param.data, dtype=loaded_weight.dtype, device="cuda"
+            )
+
+        param_data = param.data
+        tp_rank = get_tensor_model_parallel_rank()
+        input_dim = getattr(param, "input_dim", None)
+        if input_dim is not None:
+            shard_size = param.data.shape[input_dim]
+            start_idx = tp_rank * shard_size
+            loaded_weight = loaded_weight.narrow(input_dim, start_idx, shard_size)
+
+        # Special case for loading scales off disk, which often do not
+        # have a shape (such as in the case of AutoFP8).
+        if len(loaded_weight.shape) == 0:
+            loaded_weight = loaded_weight.reshape(1)
+
+        assert param_data.shape == loaded_weight.shape
+        param_data.copy_(loaded_weight)
+
+    def forward(self, input_):
+        # Set up backprop all-reduce.
+        if self.input_is_parallel:
+            input_parallel = input_
+        else:
+            tp_rank = get_tensor_model_parallel_rank()
+            splitted_input = split_tensor_along_last_dim(
+                input_, num_partitions=self.tp_size
+            )
+            input_parallel = splitted_input[tp_rank].contiguous()
+
+        # Matrix multiply.
+        assert self.quant_method is not None
+        output_parallel = self.quant_method.apply(self, input_parallel)
+        if self.reduce_results and self.tp_size > 1:
+            output_ = tensor_model_parallel_all_reduce(output_parallel)
+        else:
+            output_ = output_parallel
+
+        if not self.skip_bias_add:
+            output = output_ + self.bias if self.bias is not None else output_
+            output_bias = None
+        else:
+            output = output_
+            output_bias = self.bias
+        return output, output_bias
+
+    def extra_repr(self) -> str:
+        s = f"input_features={self.input_size_per_partition}"
+        s += f", output_features={self.output_size}"
+        s += f", bias={self.bias is not None}"
+        s += f", tp_size={self.tp_size}"
+        s += f", reduce_results={self.reduce_results}"
+        return s

python/sglang/srt/layers/quantization/__init__.py

@@ -0,0 +1,49 @@
+# temporarily adapted from vLLM
+# FIXME: in progress of refactoring the model loader
+
+from typing import Dict, Type
+
+from vllm.model_executor.layers.quantization.aqlm import AQLMConfig
+from vllm.model_executor.layers.quantization.awq import AWQConfig
+from vllm.model_executor.layers.quantization.base_config import QuantizationConfig
+from vllm.model_executor.layers.quantization.bitsandbytes import BitsAndBytesConfig
+from vllm.model_executor.layers.quantization.compressed_tensors.compressed_tensors import (  # noqa: E501
+    CompressedTensorsConfig,
+)
+from vllm.model_executor.layers.quantization.deepspeedfp import DeepSpeedFPConfig
+from vllm.model_executor.layers.quantization.gptq import GPTQConfig
+from vllm.model_executor.layers.quantization.gptq_marlin import GPTQMarlinConfig
+from vllm.model_executor.layers.quantization.gptq_marlin_24 import GPTQMarlin24Config
+from vllm.model_executor.layers.quantization.marlin import MarlinConfig
+from vllm.model_executor.layers.quantization.squeezellm import SqueezeLLMConfig
+
+from sglang.srt.layers.quantization.fp8 import Fp8Config
+
+QUANTIZATION_METHODS: Dict[str, Type[QuantizationConfig]] = {
+    "aqlm": AQLMConfig,
+    "awq": AWQConfig,
+    "deepspeedfp": DeepSpeedFPConfig,
+    "fp8": Fp8Config,
+    # The order of gptq methods is important for config.py iteration over
+    # override_quantization_method(..)
+    "marlin": MarlinConfig,
+    "gptq_marlin_24": GPTQMarlin24Config,
+    "gptq_marlin": GPTQMarlinConfig,
+    "gptq": GPTQConfig,
+    "squeezellm": SqueezeLLMConfig,
+    "compressed-tensors": CompressedTensorsConfig,
+    "bitsandbytes": BitsAndBytesConfig,
+}
+
+
+def get_quantization_config(quantization: str) -> Type[QuantizationConfig]:
+    if quantization not in QUANTIZATION_METHODS:
+        raise ValueError(f"Invalid quantization method: {quantization}")
+    return QUANTIZATION_METHODS[quantization]
+
+
+__all__ = [
+    "QuantizationConfig",
+    "get_quantization_config",
+    "QUANTIZATION_METHODS",
+]

python/sglang/srt/layers/quantization/fp8.py

@@ -0,0 +1,662 @@
+# adapted from https://github.com/vllm-project/vllm/blob/e76466dde2bc9525d55165ceaa600d298c7bf773/vllm/model_executor/layers/quantization/fp8.py
+# FIXME refactor in progress
+from typing import Any, Dict, List, Optional, Union
+
+import torch
+from torch.nn import Module
+from torch.nn.parameter import Parameter
+from vllm import _custom_ops as ops
+from vllm.logger import init_logger
+from vllm.model_executor.layers.fused_moe import FusedMoE, FusedMoEMethodBase, fused_moe
+from vllm.model_executor.layers.quantization.base_config import (
+    QuantizationConfig,
+    QuantizeMethodBase,
+)
+from vllm.model_executor.layers.quantization.gptq_marlin import (
+    GPTQ_MARLIN_MAX_PARALLEL,
+    GPTQ_MARLIN_MIN_THREAD_N,
+    GPTQMarlinState,
+    marlin_permute_scales,
+)
+from vllm.model_executor.layers.quantization.utils.marlin_utils import pack_fp8_to_int32
+from vllm.model_executor.utils import set_weight_attrs
+from vllm.platforms import current_platform
+from vllm.utils import print_warning_once
+
+from sglang.srt.layers.linear import LinearBase, LinearMethodBase
+
+ACTIVATION_SCHEMES = ["static", "dynamic"]
+
+logger = init_logger(__name__)
+
+
+def cutlass_fp8_supported() -> bool:
+    capability = current_platform.get_device_capability()
+    capability = capability[0] * 10 + capability[1]
+
+    return ops.cutlass_scaled_mm_supports_fp8(capability)
+
+
+class Fp8Config(QuantizationConfig):
+    """Config class for FP8."""
+
+    def __init__(
+        self,
+        is_checkpoint_fp8_serialized: bool = False,
+        activation_scheme: str = "dynamic",
+    ) -> None:
+        self.is_checkpoint_fp8_serialized = is_checkpoint_fp8_serialized
+        if is_checkpoint_fp8_serialized:
+            logger.warning(
+                "Detected fp8 checkpoint. Please note that the "
+                "format is experimental and subject to change."
+            )
+        if activation_scheme not in ACTIVATION_SCHEMES:
+            raise ValueError(f"Unsupported activation scheme {activation_scheme}")
+        self.activation_scheme = activation_scheme
+
+    @classmethod
+    def get_name(cls) -> str:
+        return "fp8"
+
+    @classmethod
+    def get_supported_act_dtypes(cls) -> List[torch.dtype]:
+        return [torch.bfloat16, torch.half]
+
+    @classmethod
+    def get_min_capability(cls) -> int:
+        return 80
+
+    @classmethod
+    def get_config_filenames(cls) -> List[str]:
+        return []
+
+    @classmethod
+    def from_config(cls, config: Dict[str, Any]) -> "Fp8Config":
+        quant_method = cls.get_from_keys(config, ["quant_method"])
+        is_checkpoint_fp8_serialized = "fp8" in quant_method
+        activation_scheme = cls.get_from_keys(config, ["activation_scheme"])
+        return cls(
+            is_checkpoint_fp8_serialized=is_checkpoint_fp8_serialized,
+            activation_scheme=activation_scheme,
+        )
+
+    def get_quant_method(
+        self, layer: torch.nn.Module
+    ) -> Optional["QuantizeMethodBase"]:
+
+        if isinstance(layer, LinearBase):
+            return Fp8LinearMethod(self)
+        elif isinstance(layer, FusedMoE):
+            return Fp8MoEMethod(self)
+        return None
+
+    def get_scaled_act_names(self) -> List[str]:
+        return []
+
+
+class Fp8LinearMethod(LinearMethodBase):
+    """Linear method for FP8.
+    Supports loading FP8 checkpoints with static weight scale and
+    dynamic/static activation scale.
+
+    Also supports loading quantized FP16/BF16 model checkpoints with dynamic
+    activation scaling. The weight scaling factor will be initialized after
+    the model weights are loaded.
+
+    Limitations:
+    1. Only support per-tensor quantization due to torch._scaled_mm support.
+    2. Only support float8_e4m3fn data type due to the limitation of
+       torch._scaled_mm (https://github.com/pytorch/pytorch/blob/2e48b39603411a41c5025efbe52f89560b827825/aten/src/ATen/native/cuda/Blas.cpp#L854-L856)
+
+    Args:
+        quant_config: The quantization config.
+    """
+
+    def __init__(self, quant_config: Fp8Config):
+        self.quant_config = quant_config
+        self.cutlass_fp8_supported = cutlass_fp8_supported()
+
+        # For GPUs that lack FP8 hardware support, we can leverage the Marlin
+        # kernel for fast weight-only FP8 quantization
+        capability = current_platform.get_device_capability()
+        capability = capability[0] * 10 + capability[1]
+        self.use_marlin = capability < 89
+
+    def _create_scale_param(
+        self,
+        scale_name: str,
+        layer: torch.nn.Module,
+        output_partition_sizes: List[int],
+        **extra_weight_attrs,
+    ) -> None:
+        scale = Parameter(
+            torch.empty(len(output_partition_sizes), dtype=torch.float32),
+            requires_grad=False,
+        )
+        scale[:] = torch.finfo(torch.float8_e4m3fn).min
+        layer.register_parameter(scale_name, scale)
+        set_weight_attrs(
+            scale,
+            {
+                **extra_weight_attrs,
+                "needs_scalar_to_array": True,
+            },
+        )
+
+    def create_weights(
+        self,
+        layer: torch.nn.Module,
+        input_size_per_partition: int,
+        output_partition_sizes: List[int],
+        input_size: int,
+        output_size: int,
+        params_dtype: torch.dtype,
+        **extra_weight_attrs,
+    ):
+        del input_size, output_size
+        output_size_per_partition = sum(output_partition_sizes)
+
+        layer.process_after_load = True
+        layer.logical_widths = output_partition_sizes
+
+        layer.input_size_per_partition = input_size_per_partition
+        layer.output_size_per_partition = output_size_per_partition
+        layer.orig_dtype = params_dtype
+
+        # WEIGHT
+        # weight_dtype = (torch.float8_e4m3fn
+        #                 if self.quant_config.is_checkpoint_fp8_serialized else
+        #                 params_dtype)
+        weight_dtype = torch.float8_e4m3fn
+        weight = Parameter(
+            torch.empty(
+                output_size_per_partition, input_size_per_partition, dtype=weight_dtype
+            ),
+            requires_grad=False,
+        )
+        layer.register_parameter("weight", weight)
+        set_weight_attrs(
+            weight,
+            {
+                **extra_weight_attrs,
+                "input_dim": 1,
+                "output_dim": 0,
+            },
+        )
+
+        # If checkpoint is serialized fp8, load them.
+        # Otherwise, wait until process_weights_after_loading.
+        if self.quant_config.is_checkpoint_fp8_serialized:
+            # WEIGHT SCALE
+            self._create_scale_param(
+                scale_name="weight_scale",
+                layer=layer,
+                output_partition_sizes=output_partition_sizes,
+                **extra_weight_attrs,
+            )
+
+            # INPUT ACTIVATION SCALE
+            if self.quant_config.activation_scheme == "static":
+                self._create_scale_param(
+                    scale_name="input_scale",
+                    layer=layer,
+                    output_partition_sizes=output_partition_sizes,
+                    **extra_weight_attrs,
+                )
+
+        # For GPUs without FP8 hardware support, we use Marlin for fast
+        # fused dequantization
+        if self.use_marlin:
+            layer.marlin_state = GPTQMarlinState.REPACK
+
+    def prepare_layer_for_marlin(self, layer: Module) -> None:
+        print_warning_once(
+            "Your GPU does not have native support for FP8 computation but "
+            "FP8 quantization is being used. Weight-only FP8 compression will "
+            "be used leveraging the Marlin kernel. This may degrade "
+            "performance for compute-heavy workloads."
+        )
+
+        part_size_n = layer.output_size_per_partition
+        part_size_k = layer.input_size_per_partition
+
+        assert layer.marlin_state == GPTQMarlinState.REPACK
+        layer.marlin_state = GPTQMarlinState.READY
+
+        device = layer.weight.device
+
+        # WEIGHTS
+        # Repack weights to gptq format (packed int32 elements)
+        packed_gptq_qweight = pack_fp8_to_int32(layer.weight)
+
+        # Repack weights to marlin format
+        marlin_qweight = ops.gptq_marlin_repack(
+            b_q_weight=packed_gptq_qweight,
+            perm=torch.empty(0, dtype=torch.int, device=device),
+            size_k=part_size_k,
+            size_n=part_size_n,
+            num_bits=8,
+        )
+        layer.weight = Parameter(marlin_qweight, requires_grad=False)
+
+        # WEIGHT SCALES
+        # Currently Marlin doesn't support per-tensor scales, so we
+        # expand it to channelwise
+        scales = (
+            layer.weight_scale.repeat(1, part_size_n).to(layer.orig_dtype).to(device)
+        )
+        # Permute scales
+        marlin_scales = marlin_permute_scales(
+            s=scales,
+            size_k=part_size_k,
+            size_n=part_size_n,
+            group_size=-1,
+            num_bits=8,
+        )
+        layer.weight_scale = Parameter(marlin_scales, requires_grad=False)
+
+        # Allocate marlin workspace
+        max_workspace_size = (
+            part_size_n // GPTQ_MARLIN_MIN_THREAD_N
+        ) * GPTQ_MARLIN_MAX_PARALLEL
+        workspace = torch.zeros(
+            max_workspace_size, dtype=torch.int, device=device, requires_grad=False
+        )
+
+        layer.workspace = workspace
+
+    def process_weights_after_loading(self, layer: Module) -> None:
+        if not hasattr(layer, "process_after_load") or not layer.process_after_load:
+            return
+
+        # If checkpoint is fp/bf16 (not serialized fp8), quantize the weights.
+        if not self.quant_config.is_checkpoint_fp8_serialized:
+            qweight, weight_scale = ops.scaled_fp8_quant(layer.weight, scale=None)
+            layer.weight = Parameter(qweight.t(), requires_grad=False)
+            layer.weight_scale = Parameter(weight_scale, requires_grad=False)
+            layer.logical_widths = None
+            layer.input_scale = None
+            if self.use_marlin:
+                self.prepare_layer_for_marlin(layer)
+            return
+
+        # If checkpoint is fp8, requantize the separately quantized logical
+        # weights into a single fp8 weight with a single weight scale.
+        else:
+            # WEIGHT_SCALE / WEIGHT
+            #   Loop over logical weights, requantizing with single scale.
+            max_w_scale = layer.weight_scale.max()
+
+            # QKV / MLP is fused in the on disk checkpoint if any of the
+            # weight scales are still set to the default since we initialize
+            # N weight scales for N shards but we only load 1 weight scale
+            # from disk in this case. As a result, we skip dequant -> requant
+            # since we already have quantized QKV together.
+            # Sample Model with fused checkpoint:
+            #   * nm-testing/Phi-3-mini-128k-instruct-FP8
+            unfused_module_in_checkpoint = (
+                layer.weight_scale[-1] > torch.finfo(torch.float8_e4m3fn).min
+            )
+
+            if unfused_module_in_checkpoint:
+                start = 0
+                for idx, logical_width in enumerate(layer.logical_widths):
+                    end = start + logical_width
+                    weight_dq = per_tensor_dequantize(
+                        layer.weight[start:end, :], layer.weight_scale[idx]
+                    )
+
+                    layer.weight[start:end, :] = per_tensor_quantize(
+                        weight_dq, layer.weight_scale.max()
+                    )
+                    start = end
+            layer.weight_scale = Parameter(max_w_scale, requires_grad=False)
+
+            # WEIGHT
+            #   Transpose weight for passing to torch._scaled_mm
+            weight = layer.weight
+            layer.weight = Parameter(weight.t(), requires_grad=False)
+
+            # INPUT ACTIVATION SCALE
+            #   Dynamic: set to None (required input to ops.scaled_fp8_quant).
+            #   Static:  set to max of the input_scales (since they are equal).
+            if self.quant_config.activation_scheme == "dynamic":
+                layer.input_scale = None
+            elif self.quant_config.activation_scheme == "static":
+                layer.input_scale = Parameter(
+                    layer.input_scale.max(), requires_grad=False
+                )
+            else:
+                raise ValueError(
+                    f"Unknown scheme {self.quant_config.activation_scheme}"
+                )
+
+            if self.use_marlin:
+                self.prepare_layer_for_marlin(layer)
+
+    def apply(
+        self,
+        layer: torch.nn.Module,
+        x: torch.Tensor,
+        bias: Optional[torch.Tensor] = None,
+    ) -> torch.Tensor:
+
+        if self.use_marlin:
+            # For GPUs that lack FP8 hardware support, we can leverage the
+            # Marlin kernel for fast weight-only FP8 quantization
+
+            reshaped_x = x.reshape(-1, x.shape[-1])
+            out_shape = x.shape[:-1] + (layer.output_size_per_partition,)
+
+            output = ops.fp8_marlin_gemm(
+                a=reshaped_x,
+                b_q_weight=layer.weight,
+                b_scales=layer.weight_scale,
+                workspace=layer.workspace,
+                num_bits=8,
+                size_m=reshaped_x.shape[0],
+                size_n=layer.output_size_per_partition,
+                size_k=layer.input_size_per_partition,
+            )
+
+            if bias is not None:
+                output.add_(bias)  # In-place add
+
+            return output.reshape(out_shape)
+
+        else:
+
+            # ops.scaled_fp8_quant supports both dynamic and static quant.
+            # If dynamic, layer.input_scale is None and x_scale computed from x
+            # If static, layer.input_scale is scalar and x_scale is input_scale
+
+            if bias is None and self.cutlass_fp8_supported:
+                qinput, x_scale = ops.scaled_fp8_quant(x, layer.input_scale)
+
+                # Fused GEMM_DQ
+                output = ops.cutlass_scaled_mm(
+                    qinput,
+                    layer.weight,
+                    out_dtype=x.dtype,
+                    scale_a=x_scale,
+                    scale_b=layer.weight_scale,
+                )
+
+            else:
+                qinput, x_scale = ops.scaled_fp8_quant(
+                    x, layer.input_scale, batch_dim_padding=17
+                )
+
+                # Fused GEMM_DQ -- note we padded the input above because
+                # torch._scaled_mm is more performant for matrices with
+                # batch dimension > 16. Note that this could change
+                # in the future.
+                output, _ = torch._scaled_mm(
+                    qinput,
+                    layer.weight,
+                    out_dtype=x.dtype,
+                    scale_a=x_scale,
+                    scale_b=layer.weight_scale,
+                    bias=bias,
+                )
+
+        return torch.narrow(output, 0, 0, x.shape[0])
+
+
+class Fp8MoEMethod(FusedMoEMethodBase):
+    """MoE method for FP8.
+    Supports loading FP8 checkpoints with static weight scale and
+    dynamic/static activation scale.
+
+    Also supports loading quantized FP16/BF16 model checkpoints with dynamic
+    activation scaling. The weight scaling factor will be initialized after
+    the model weights are loaded.
+
+    Args:
+        quant_config: The quantization config.
+    """
+
+    def __init__(self, quant_config: Fp8Config):
+        self.quant_config = quant_config
+
+    def create_weights(
+        self,
+        layer: Module,
+        num_experts: int,
+        hidden_size: int,
+        intermediate_size: int,
+        params_dtype: torch.dtype,
+        **extra_weight_attrs,
+    ):
+
+        layer.process_after_load = True
+
+        if self.quant_config.is_checkpoint_fp8_serialized:
+            params_dtype = torch.float8_e4m3fn
+
+        # WEIGHTS
+        w13_weight = torch.nn.Parameter(
+            torch.empty(
+                num_experts, 2 * intermediate_size, hidden_size, dtype=params_dtype
+            ),
+            requires_grad=False,
+        )
+        layer.register_parameter("w13_weight", w13_weight)
+        set_weight_attrs(w13_weight, extra_weight_attrs)
+
+        w2_weight = torch.nn.Parameter(
+            torch.empty(
+                num_experts, hidden_size, intermediate_size, dtype=params_dtype
+            ),
+            requires_grad=False,
+        )
+        layer.register_parameter("w2_weight", w2_weight)
+        set_weight_attrs(w2_weight, extra_weight_attrs)
+
+        # WEIGHT_SCALES
+        # Allocate 2 scales for w1 and w3 respectively.
+        # They will be combined to a single scale after weight loading.
+        w13_scale = torch.nn.Parameter(
+            torch.ones(num_experts, 2, dtype=torch.float32), requires_grad=False
+        )
+        layer.register_parameter("w13_scale", w13_scale)
+
+        w2_scale = torch.nn.Parameter(
+            torch.ones(num_experts, dtype=torch.float32), requires_grad=False
+        )
+        layer.register_parameter("w2_scale", w2_scale)
+
+        # If loading fp8 checkpoint, pass the weight loaders.
+        # If loading an fp16 checkpoint, do not (we will quantize in
+        #   process_weights_after_loading()
+        if self.quant_config.is_checkpoint_fp8_serialized:
+            set_weight_attrs(w13_scale, extra_weight_attrs)
+            set_weight_attrs(w2_scale, extra_weight_attrs)
+
+        # INPUT_SCALES
+        if self.quant_config.activation_scheme == "static":
+            if not self.quant_config.is_checkpoint_fp8_serialized:
+                raise ValueError(
+                    "Found static activation scheme for checkpoint that "
+                    "was not serialized fp8."
+                )
+
+            a13_scale = torch.nn.Parameter(
+                torch.ones(num_experts, dtype=torch.float32), requires_grad=False
+            )
+            layer.register_parameter("a13_scale", a13_scale)
+            set_weight_attrs(a13_scale, extra_weight_attrs)
+
+            a2_scale = torch.nn.Parameter(
+                torch.ones(num_experts, dtype=torch.float32), requires_grad=False
+            )
+            layer.register_parameter("a2_scale", a2_scale)
+            set_weight_attrs(a2_scale, extra_weight_attrs)
+        else:
+            layer.a13_scale = None
+            layer.a2_scale = None
+
+    def process_weights_after_loading(self, layer: Module) -> None:
+        if not hasattr(layer, "process_after_load") or not layer.process_after_load:
+            return
+
+        # If checkpoint is fp16, quantize in place.
+        if not self.quant_config.is_checkpoint_fp8_serialized:
+            w13_weight = torch.empty_like(
+                layer.w13_weight.data, dtype=torch.float8_e4m3fn
+            )
+            w2_weight = torch.empty_like(
+                layer.w2_weight.data, dtype=torch.float8_e4m3fn
+            )
+
+            # Re-initialize w13_scale because we directly quantize
+            # merged w13 weights and generate a single scaling factor.
+            layer.w13_scale = torch.nn.Parameter(
+                torch.ones(
+                    layer.num_experts, dtype=torch.float32, device=w13_weight.device
+                ),
+                requires_grad=False,
+            )
+            for expert in range(layer.num_experts):
+                w13_weight[expert, :, :], layer.w13_scale[expert] = (
+                    ops.scaled_fp8_quant(layer.w13_weight.data[expert, :, :])
+                )
+                w2_weight[expert, :, :], layer.w2_scale[expert] = ops.scaled_fp8_quant(
+                    layer.w2_weight.data[expert, :, :]
+                )
+            layer.w13_weight = torch.nn.Parameter(w13_weight, requires_grad=False)
+            layer.w2_weight = torch.nn.Parameter(w2_weight, requires_grad=False)
+            return
+
+        # If checkpoint is fp8, we need to handle that the
+        # MoE kernels require single activation scale and single weight
+        # scale for w13 per expert.
+        else:
+            # Fp8 moe kernels require a single activation scale.
+            # We take the max of all the scales in case they differ.
+            if self.quant_config.activation_scheme == "static":
+                if layer.a13_scale is None or layer.a2_scale is None:
+                    raise ValueError(
+                        "QuantConfig has static quantization, but found "
+                        "activation scales are None."
+                    )
+                if not all_close_1d(layer.a13_scale) or not all_close_1d(
+                    layer.a2_scale
+                ):
+                    print_warning_once(
+                        "Found input_scales that are not equal for "
+                        "fp8 MoE layer. Using the maximum across experts "
+                        "for each layer. "
+                    )
+                layer.a13_scale = torch.nn.Parameter(
+                    layer.a13_scale.max(), requires_grad=False
+                )
+                layer.a2_scale = torch.nn.Parameter(
+                    layer.a2_scale.max(), requires_grad=False
+                )
+
+            # Fp8 moe kernel needs single weight scale for w13 per expert.
+            # We take the max then dequant and requant each expert.
+            assert layer.w13_scale is not None
+            shard_size = layer.intermediate_size_per_partition
+            max_w13_scales = layer.w13_scale.max(dim=1).values
+            for expert_id in range(layer.num_experts):
+                start = 0
+                for shard_id in range(2):
+                    dq_weight = per_tensor_dequantize(
+                        layer.w13_weight[expert_id][start : start + shard_size, :],
+                        layer.w13_scale[expert_id][shard_id],
+                    )
+                    layer.w13_weight[expert_id][start : start + shard_size, :] = (
+                        per_tensor_quantize(dq_weight, max_w13_scales[expert_id])
+                    )
+                    start += shard_size
+
+            layer.w13_scale = torch.nn.Parameter(max_w13_scales, requires_grad=False)
+            return
+
+    def apply(
+        self,
+        layer: torch.nn.Module,
+        x: torch.Tensor,
+        router_logits: torch.Tensor,
+        top_k: int,
+        renormalize: bool = True,
+    ) -> torch.Tensor:
+
+        return fused_moe(
+            x,
+            layer.w13_weight,
+            layer.w2_weight,
+            router_logits,
+            top_k,
+            renormalize=renormalize,
+            inplace=True,
+            use_fp8=True,
+            w1_scale=layer.w13_scale,
+            w2_scale=layer.w2_scale,
+            a1_scale=layer.a13_scale,
+            a2_scale=layer.a2_scale,
+        )
+
+
+# FIXME: not used
+class Fp8KVCacheMethod(QuantizeMethodBase):
+    """Supports loading kv-cache scaling factors from FP8 checkpoints."""
+
+    def __init__(self, quant_config: Fp8Config):
+        self.quant_config = quant_config
+
+    def create_weights(self, layer: torch.nn.Module):
+        """Create "weight" (aka kv_scale) for an attention layer.
+
+        Args:
+            layer: The layer that is using the QuantizeMethodBase factory.
+        """
+        # Initialize the KV cache scale to 1.0 as the default value.
+        # If the kv_scale appears in the checkpoint, it will be
+        # overwritten when loading weights.
+        layer.kv_scale = Parameter(torch.tensor(1.0), requires_grad=False)
+
+    def apply(self, layer: torch.nn.Module) -> torch.Tensor:
+        raise RuntimeError("Fp8KVCacheMethod.apply should not be called.")
+
+    def process_weights_after_loading(self, layer: Module) -> None:
+        # If the kv-cache dtype is auto, we enforce the kv-scale to be 1.0
+        # regardless whether the kv-scale is available in the checkpoint.
+        if layer.kv_cache_dtype != "auto":
+            kv_scale = layer.kv_scale.to("cpu").tolist()
+            if not isinstance(kv_scale, float):
+                raise ValueError(
+                    "Only support per-tensor scaling factor " "for fp8 KV cache"
+                )
+            layer._kv_scale = kv_scale
+            if layer._kv_scale == 1.0 and "e5m2" not in layer.kv_cache_dtype:
+                print_warning_once(
+                    "Using KV cache scaling factor 1.0 for fp8_e4m3. This may "
+                    "cause accuracy issues. Please make sure kv-cache scaling "
+                    "factor is available in the fp8 checkpoint."
+                )
+        del layer.kv_scale
+
+
+def per_tensor_quantize(
+    tensor: torch.Tensor, inv_scale: Union[float, torch.Tensor]
+) -> torch.Tensor:
+    finfo = torch.finfo(torch.float8_e4m3fn)
+    qweight = (tensor / inv_scale).clamp(min=finfo.min, max=finfo.max)
+    return qweight.to(torch.float8_e4m3fn)
+
+
+def per_tensor_dequantize(
+    tensor: torch.Tensor, inv_scale: Union[float, torch.Tensor]
+) -> torch.Tensor:
+    fake_qweight = tensor.to(torch.float16)
+    dq_weight = fake_qweight * inv_scale
+    return dq_weight
+
+
+def all_close_1d(x: torch.Tensor) -> bool:
+    assert len(x.shape) == 1
+    return all(torch.allclose(x[0], x[i]) for i in range(x.shape[0]))

python/sglang/srt/model_loader/model_loader.py

@@ -0,0 +1,276 @@
+# temporarily adapted from https://github.com/vllm-project/vllm/blob/10383887e03412196a2689b9398290719c4797bf/vllm/model_executor/model_loader/loader.py
+# FIXME: in progress of refactoring the model loader
+
+import glob
+import os
+import re
+from typing import Any, Dict, Generator, List, Optional, Tuple, Type
+
+import torch
+from torch import nn
+from tqdm import tqdm
+from vllm.config import (
+    CacheConfig,
+    DeviceConfig,
+    LoadConfig,
+    LoadFormat,
+    LoRAConfig,
+    ModelConfig,
+    MultiModalConfig,
+    ParallelConfig,
+    SchedulerConfig,
+)
+from vllm.model_executor.layers.quantization.base_config import QuantizationConfig
+from vllm.model_executor.model_loader.utils import (
+    get_model_architecture,
+    set_default_torch_dtype,
+)
+from vllm.platforms import current_platform
+
+from sglang.srt.model_loader.utils import (
+    download_safetensors_index_file_from_hf,
+    download_weights_from_hf,
+    filter_duplicate_safetensors_files,
+    get_quant_config,
+    safetensors_weights_iterator,
+)
+
+
+def _get_quantization_config(
+    model_config: ModelConfig, load_config: LoadConfig
+) -> Optional[QuantizationConfig]:
+    """Get the quantization config."""
+    if model_config.quantization is not None:
+        quant_config = get_quant_config(model_config, load_config)
+        capability = current_platform.get_device_capability()
+        capability = capability[0] * 10 + capability[1]
+        if capability < quant_config.get_min_capability():
+            raise ValueError(
+                f"The quantization method {model_config.quantization} is not "
+                "supported for the current GPU. "
+                f"Minimum capability: {quant_config.get_min_capability()}. "
+                f"Current capability: {capability}."
+            )
+        supported_dtypes = quant_config.get_supported_act_dtypes()
+        if model_config.dtype not in supported_dtypes:
+            raise ValueError(
+                f"{model_config.dtype} is not supported for quantization "
+                f"method {model_config.quantization}. Supported dtypes: "
+                f"{supported_dtypes}"
+            )
+        return quant_config
+    return None
+
+
+def _get_model_initialization_kwargs(
+    model_class: Type[nn.Module],
+    lora_config: Optional[LoRAConfig],
+    multimodal_config: Optional[MultiModalConfig],
+) -> Dict[str, Any]:
+    """Get extra kwargs for model initialization."""
+    extra_kwargs: Dict[str, Any] = {}
+
+    assert lora_config is None
+    assert multimodal_config is None
+
+    return extra_kwargs
+
+
+def _initialize_model(
+    model_config: ModelConfig,
+    load_config: LoadConfig,
+    lora_config: Optional[LoRAConfig],
+    multimodal_config: Optional[MultiModalConfig],
+    cache_config: CacheConfig,
+) -> nn.Module:
+    """Initialize a model with the given configurations."""
+    model_class = get_model_architecture(model_config)[0]
+    quant_config = _get_quantization_config(model_config, load_config)
+
+    return model_class(
+        config=model_config.hf_config,
+        cache_config=cache_config,
+        quant_config=quant_config,
+        **_get_model_initialization_kwargs(model_class, lora_config, multimodal_config),
+    )
+
+
+class ModelLoader:
+    """Model loader that can load different file types from disk."""
+
+    def __init__(self, load_config: LoadConfig):
+        self.load_config = load_config
+
+    def _prepare_weights(
+        self, model_name_or_path: str, revision: Optional[str], fall_back_to_pt: bool
+    ) -> Tuple[str, List[str], bool]:
+        """Prepare weights for the model.
+
+        If the model is not local, it will be downloaded."""
+
+        is_local = os.path.isdir(model_name_or_path)
+        load_format = self.load_config.load_format
+        use_safetensors = False
+        # Some quantized models use .pt files for storing the weights.
+        if load_format == LoadFormat.AUTO:
+            allow_patterns = ["*.safetensors", "*.bin"]
+        elif load_format == LoadFormat.SAFETENSORS:
+            use_safetensors = True
+            allow_patterns = ["*.safetensors"]
+        elif load_format == LoadFormat.PT:
+            allow_patterns = ["*.pt"]
+        elif load_format == LoadFormat.NPCACHE:
+            allow_patterns = ["*.bin"]
+        else:
+            raise ValueError(f"Unknown load_format: {load_format}")
+
+        if fall_back_to_pt:
+            allow_patterns += ["*.pt"]
+
+        if not is_local:
+            hf_folder = download_weights_from_hf(
+                model_name_or_path,
+                self.load_config.download_dir,
+                allow_patterns,
+                revision,
+            )
+        else:
+            hf_folder = model_name_or_path
+
+        hf_weights_files: List[str] = []
+        for pattern in allow_patterns:
+            hf_weights_files += glob.glob(os.path.join(hf_folder, pattern))
+            if len(hf_weights_files) > 0:
+                if pattern == "*.safetensors":
+                    use_safetensors = True
+                break
+
+        if use_safetensors:
+            # For models like Mistral-7B-Instruct-v0.3
+            # there are both sharded safetensors files and a consolidated
+            # safetensors file. Using both breaks.
+            # Here, we download the `model.safetensors.index.json` and filter
+            # any files not found in the index.
+            if not is_local:
+                download_safetensors_index_file_from_hf(
+                    model_name_or_path, self.load_config.download_dir, revision
+                )
+            hf_weights_files = filter_duplicate_safetensors_files(
+                hf_weights_files, hf_folder
+            )
+        else:
+            hf_weights_files = filter_files_not_needed_for_inference(hf_weights_files)
+
+        if len(hf_weights_files) == 0:
+            raise RuntimeError(
+                f"Cannot find any model weights with `{model_name_or_path}`"
+            )
+
+        return hf_folder, hf_weights_files, use_safetensors
+
+    def _get_weights_iterator(
+        self, model_name_or_path: str, revision: Optional[str], fall_back_to_pt: bool
+    ) -> Generator[Tuple[str, torch.Tensor], None, None]:
+        """Get an iterator for the model weights based on the load format."""
+        hf_folder, hf_weights_files, use_safetensors = self._prepare_weights(
+            model_name_or_path, revision, fall_back_to_pt
+        )
+        if self.load_config.load_format == LoadFormat.NPCACHE:
+            # Currently np_cache only support *.bin checkpoints
+            assert use_safetensors is False
+            weights_iterator = np_cache_weights_iterator(
+                model_name_or_path,
+                self.load_config.download_dir,
+                hf_folder,
+                hf_weights_files,
+            )
+        elif use_safetensors:
+            weights_iterator = safetensors_weights_iterator(hf_weights_files)
+        else:
+            weights_iterator = pt_weights_iterator(hf_weights_files)
+
+        return weights_iterator
+
+    def load_model(
+        self,
+        *,
+        model_config: ModelConfig,
+        device_config: DeviceConfig,
+        lora_config: Optional[LoRAConfig],
+        multimodal_config: Optional[MultiModalConfig],
+        parallel_config: ParallelConfig,
+        scheduler_config: SchedulerConfig,
+        cache_config: CacheConfig,
+    ) -> nn.Module:
+        with set_default_torch_dtype(model_config.dtype):
+            with torch.device(device_config.device):
+                model = _initialize_model(
+                    model_config,
+                    self.load_config,
+                    lora_config,
+                    multimodal_config,
+                    cache_config,
+                )
+            weights = self._get_weights_iterator(
+                model_config.model,
+                model_config.revision,
+                fall_back_to_pt=getattr(model, "fall_back_to_pt_during_load", True),
+            )
+
+            modules = {}
+            for name, module in model.named_modules():
+                modules[name] = module
+
+            def apply_quant_method(module):
+                quant_method = getattr(module, "quant_method", None)
+                if quant_method is not None:
+                    # print("before apply quant", module.weight, module.weight.dtype)
+                    quant_method.process_weights_after_loading(module)
+                    # print("after apply quant", module.weight, module.weight.dtype)
+                # FIXME: Remove this after Mixtral is updated
+                # to use quant_method.
+                if hasattr(module, "process_weights_after_loading"):
+                    module.process_weights_after_loading()
+
+            if torch.cuda.current_device() == 0:
+                weights = tqdm(
+                    weights, total=model.get_num_params() * 1.5, desc="load model"
+                )
+
+            num_shard = {}
+            num_loaded = {}
+            for name, loaded_weight in weights:
+                model.load_weights(None, name, loaded_weight)
+                module_name, shard_num = model.get_module_name(name)
+                num_shard[module_name] = shard_num
+                if module_name not in num_loaded:
+                    num_loaded[module_name] = 1
+                else:
+                    num_loaded[module_name] += 1
+                if num_loaded[module_name] == num_shard[module_name]:
+                    apply_quant_method(modules[module_name])
+
+        return model.eval()
+
+
+def get_model(
+    *,
+    model_config: ModelConfig,
+    load_config: LoadConfig,
+    device_config: DeviceConfig,
+    parallel_config: ParallelConfig,
+    scheduler_config: SchedulerConfig,
+    lora_config: Optional[LoRAConfig],
+    multimodal_config: Optional[MultiModalConfig],
+    cache_config: CacheConfig,
+) -> nn.Module:
+    loader = ModelLoader(load_config)
+    return loader.load_model(
+        model_config=model_config,
+        device_config=device_config,
+        lora_config=lora_config,
+        multimodal_config=multimodal_config,
+        parallel_config=parallel_config,
+        scheduler_config=scheduler_config,
+        cache_config=cache_config,
+    )

python/sglang/srt/model_loader/utils.py

@@ -0,0 +1,260 @@
+# temporarily adapted from vLLM
+# FIXME: in progress of refactoring the model loader
+"""Utilities for selecting and loading models."""
+import contextlib
+import fnmatch
+import hashlib
+import json
+import logging
+import os
+import tempfile
+from typing import Any, Generator, Iterable, List, Optional, Tuple, Type
+
+import filelock
+import huggingface_hub.constants
+import torch
+from huggingface_hub import HfFileSystem, hf_hub_download, snapshot_download
+from safetensors.torch import load_file, safe_open, save_file
+from torch import nn
+from tqdm.auto import tqdm
+from transformers.utils import SAFE_WEIGHTS_INDEX_NAME
+from vllm.config import LoadConfig, ModelConfig
+from vllm.model_executor.layers.quantization.base_config import QuantizationConfig
+
+from sglang.srt.layers.quantization import get_quantization_config
+
+logger = logging.getLogger("srt.model_loader")
+temp_dir = tempfile.gettempdir()
+
+
+@contextlib.contextmanager
+def set_default_torch_dtype(dtype: torch.dtype):
+    """Sets the default torch dtype to the given dtype."""
+    old_dtype = torch.get_default_dtype()
+    torch.set_default_dtype(dtype)
+    yield
+    torch.set_default_dtype(old_dtype)
+
+
+def get_model_architecture(model_config: ModelConfig) -> Tuple[Type[nn.Module], str]:
+    architectures = getattr(model_config.hf_config, "architectures", [])
+    # Special handling for quantized Mixtral.
+    # FIXME(woosuk): This is a temporary hack.
+    if (
+        model_config.quantization is not None
+        and model_config.quantization != "fp8"
+        and "MixtralForCausalLM" in architectures
+    ):
+        architectures = ["QuantMixtralForCausalLM"]
+
+    for arch in architectures:
+        model_cls = ModelRegistry.load_model_cls(arch)
+        if model_cls is not None:
+            return (model_cls, arch)
+    raise ValueError(
+        f"Model architectures {architectures} are not supported for now. "
+        f"Supported architectures: {ModelRegistry.get_supported_archs()}"
+    )
+
+
+class DisabledTqdm(tqdm):
+
+    def __init__(self, *args, **kwargs):
+        super().__init__(*args, **kwargs, disable=True)
+
+
+def get_lock(model_name_or_path: str, cache_dir: Optional[str] = None):
+    lock_dir = cache_dir or temp_dir
+    os.makedirs(os.path.dirname(lock_dir), exist_ok=True)
+    model_name = model_name_or_path.replace("/", "-")
+    hash_name = hashlib.sha256(model_name.encode()).hexdigest()
+    # add hash to avoid conflict with old users' lock files
+    lock_file_name = hash_name + model_name + ".lock"
+    # mode 0o666 is required for the filelock to be shared across users
+    lock = filelock.FileLock(os.path.join(lock_dir, lock_file_name), mode=0o666)
+    return lock
+
+
+def download_weights_from_hf(
+    model_name_or_path: str,
+    cache_dir: Optional[str],
+    allow_patterns: List[str],
+    revision: Optional[str] = None,
+) -> str:
+    """Download model weights from Hugging Face Hub.
+
+    Args:
+        model_name_or_path (str): The model name or path.
+        cache_dir (Optional[str]): The cache directory to store the model
+            weights. If None, will use HF defaults.
+        allow_patterns (List[str]): The allowed patterns for the
+            weight files. Files matched by any of the patterns will be
+            downloaded.
+        revision (Optional[str]): The revision of the model.
+
+    Returns:
+        str: The path to the downloaded model weights.
+    """
+    if not huggingface_hub.constants.HF_HUB_OFFLINE:
+        # Before we download we look at that is available:
+        fs = HfFileSystem()
+        file_list = fs.ls(model_name_or_path, detail=False, revision=revision)
+
+        # depending on what is available we download different things
+        for pattern in allow_patterns:
+            matching = fnmatch.filter(file_list, pattern)
+            if len(matching) > 0:
+                allow_patterns = [pattern]
+                break
+
+    logger.info("Using model weights format %s", allow_patterns)
+    # Use file lock to prevent multiple processes from
+    # downloading the same model weights at the same time.
+    with get_lock(model_name_or_path, cache_dir):
+        hf_folder = snapshot_download(
+            model_name_or_path,
+            allow_patterns=allow_patterns,
+            cache_dir=cache_dir,
+            tqdm_class=DisabledTqdm,
+            revision=revision,
+            local_files_only=huggingface_hub.constants.HF_HUB_OFFLINE,
+        )
+    return hf_folder
+
+
+def download_safetensors_index_file_from_hf(
+    model_name_or_path: str,
+    cache_dir: Optional[str],
+    revision: Optional[str] = None,
+) -> None:
+    """Download hf safetensors index file from Hugging Face Hub.
+
+    Args:
+        model_name_or_path (str): The model name or path.
+        cache_dir (Optional[str]): The cache directory to store the model
+            weights. If None, will use HF defaults.
+        revision (Optional[str]): The revision of the model.
+    """
+    # Use file lock to prevent multiple processes from
+    # downloading the same model weights at the same time.
+    with get_lock(model_name_or_path, cache_dir):
+        try:
+            # Download the safetensors index file.
+            hf_hub_download(
+                repo_id=model_name_or_path,
+                filename=SAFE_WEIGHTS_INDEX_NAME,
+                cache_dir=cache_dir,
+                revision=revision,
+                local_files_only=huggingface_hub.constants.HF_HUB_OFFLINE,
+            )
+        # If file not found on remote or locally, we should not fail since
+        # only some models will have SAFE_WEIGHTS_INDEX_NAME.
+        except huggingface_hub.utils.EntryNotFoundError:
+            logger.info("No %s found in remote.", SAFE_WEIGHTS_INDEX_NAME)
+        except huggingface_hub.utils.LocalEntryNotFoundError:
+            logger.info("No %s found in local cache.", SAFE_WEIGHTS_INDEX_NAME)
+
+
+# For models like Mistral-7B-v0.3, there are both sharded
+# safetensors files and a consolidated safetensors file.
+# Passing both of these to the weight loader functionality breaks.
+# So, we use the SAFE_WEIGHTS_INDEX_NAME to
+# look up which safetensors files should be used.
+def filter_duplicate_safetensors_files(
+    hf_weights_files: List[str], hf_folder: str
+) -> List[str]:
+    # model.safetensors.index.json is a mapping from keys in the
+    # torch state_dict to safetensors file holding that weight.
+    index_file_name = os.path.join(hf_folder, SAFE_WEIGHTS_INDEX_NAME)
+    if not os.path.isfile(index_file_name):
+        return hf_weights_files
+
+    # Iterate through the weight_map (weight_name: safetensors files)
+    # to identify weights that we should use.
+    with open(index_file_name) as index_file:
+        weight_map = json.load(index_file)["weight_map"]
+    weight_files_in_index = set()
+    for weight_name in weight_map:
+        weight_files_in_index.add(os.path.join(hf_folder, weight_map[weight_name]))
+    # Filter out any fields that are not found in the index file.
+    hf_weights_files = [f for f in hf_weights_files if f in weight_files_in_index]
+    return hf_weights_files
+
+
+def safetensors_weights_iterator(
+    hf_weights_files: List[str],
+) -> Generator[Tuple[str, torch.Tensor], None, None]:
+    """Iterate over the weights in the model safetensor files."""
+    for st_file in hf_weights_files:
+        with safe_open(st_file, framework="pt") as f:
+            for name in f.keys():  # noqa: SIM118
+                param = f.get_tensor(name)
+                yield name, param
+
+
+def get_quant_config(
+    model_config: ModelConfig, load_config: LoadConfig
+) -> QuantizationConfig:
+    quant_cls = get_quantization_config(model_config.quantization)
+    # Read the quantization config from the HF model config, if available.
+    hf_quant_config = getattr(model_config.hf_config, "quantization_config", None)
+    if hf_quant_config is None:
+        # compressed-tensors uses a compressions_config
+        hf_quant_config = getattr(model_config.hf_config, "compression_config", None)
+    if hf_quant_config is not None:
+        return quant_cls.from_config(hf_quant_config)
+    # In case of bitsandbytes/QLoRA, get quant config from the adapter model.
+    if model_config.quantization == "bitsandbytes":
+        if (
+            not load_config.model_loader_extra_config
+            or "qlora_adapter_name_or_path" not in load_config.model_loader_extra_config
+        ):
+            return quant_cls.from_config({"adapter_name_or_path": ""})
+        model_name_or_path = load_config.model_loader_extra_config[
+            "qlora_adapter_name_or_path"
+        ]
+
+    else:
+        model_name_or_path = model_config.model
+    is_local = os.path.isdir(model_name_or_path)
+    if not is_local:
+        # Download the config files.
+        with get_lock(model_name_or_path, load_config.download_dir):
+            hf_folder = snapshot_download(
+                model_name_or_path,
+                revision=model_config.revision,
+                allow_patterns="*.json",
+                cache_dir=load_config.download_dir,
+                local_files_only=huggingface_hub.constants.HF_HUB_OFFLINE,
+                tqdm_class=DisabledTqdm,
+            )
+    else:
+        hf_folder = model_name_or_path
+
+    possible_config_filenames = quant_cls.get_config_filenames()
+
+    # If the quantization config is not found, use the default config.
+    if not possible_config_filenames:
+        return quant_cls()
+
+    config_files = glob.glob(os.path.join(hf_folder, "*.json"))
+
+    quant_config_files = [
+        f for f in config_files if any(f.endswith(x) for x in possible_config_filenames)
+    ]
+    if len(quant_config_files) == 0:
+        raise ValueError(f"Cannot find the config file for {model_config.quantization}")
+    if len(quant_config_files) > 1:
+        raise ValueError(
+            f"Found multiple config files for {model_config.quantization}: "
+            f"{quant_config_files}"
+        )
+
+    quant_config_file = quant_config_files[0]
+    with open(quant_config_file, "r") as f:
+        config = json.load(f)
+
+        if model_config.quantization == "bitsandbytes":
+            config["adapter_name_or_path"] = model_name_or_path
+
+    return quant_cls.from_config(config)