sglang quant module remove vllm dependency (#4507)

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

@@ -6,21 +6,41 @@ from copy import deepcopy
 from typing import Callable, Dict, Optional, Type, Union
 
 import torch
-from vllm.model_executor.layers.quantization.aqlm import AQLMConfig
-from vllm.model_executor.layers.quantization.awq import AWQConfig
-from vllm.model_executor.layers.quantization.awq_marlin import AWQMarlinConfig
-from vllm.model_executor.layers.quantization.bitsandbytes import BitsAndBytesConfig
-from vllm.model_executor.layers.quantization.compressed_tensors.compressed_tensors import (
-    CompressedTensorsConfig,
-)
-from vllm.model_executor.layers.quantization.deepspeedfp import DeepSpeedFPConfig
-from vllm.model_executor.layers.quantization.experts_int8 import ExpertsInt8Config
-from vllm.model_executor.layers.quantization.fbgemm_fp8 import FBGEMMFp8Config
-from vllm.model_executor.layers.quantization.gguf import GGUFConfig
-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.qqq import QQQConfig
-from vllm.model_executor.layers.quantization.tpu_int8 import Int8TpuConfig
+
+try:
+    from vllm.model_executor.layers.quantization.aqlm import AQLMConfig
+    from vllm.model_executor.layers.quantization.awq import AWQConfig
+    from vllm.model_executor.layers.quantization.awq_marlin import AWQMarlinConfig
+    from vllm.model_executor.layers.quantization.bitsandbytes import BitsAndBytesConfig
+    from vllm.model_executor.layers.quantization.compressed_tensors.compressed_tensors import (
+        CompressedTensorsConfig,
+    )
+    from vllm.model_executor.layers.quantization.deepspeedfp import DeepSpeedFPConfig
+    from vllm.model_executor.layers.quantization.experts_int8 import ExpertsInt8Config
+    from vllm.model_executor.layers.quantization.fbgemm_fp8 import FBGEMMFp8Config
+    from vllm.model_executor.layers.quantization.gguf import GGUFConfig
+    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.qqq import QQQConfig
+    from vllm.model_executor.layers.quantization.tpu_int8 import Int8TpuConfig
+
+    VLLM_AVAILABLE = True
+except ImportError:
+    VLLM_AVAILABLE = False
+
+    # Define empty classes as placeholders when vllm is not available
+    class DummyConfig:
+        pass
+
+    AQLMConfig = AWQConfig = AWQMarlinConfig = BitsAndBytesConfig = (
+        CompressedTensorsConfig
+    ) = DummyConfig
+    DeepSpeedFPConfig = ExpertsInt8Config = FBGEMMFp8Config = GGUFConfig = (
+        GPTQMarlin24Config
+    ) = DummyConfig
+    MarlinConfig = QQQConfig = Int8TpuConfig = DummyConfig
 
 from sglang.srt.layers.quantization.base_config import QuantizationConfig
 from sglang.srt.layers.quantization.blockwise_int8 import BlockInt8Config
@@ -30,29 +50,37 @@ from sglang.srt.layers.quantization.modelopt_quant import ModelOptFp8Config
 from sglang.srt.layers.quantization.w8a8_fp8 import W8A8Fp8Config
 from sglang.srt.layers.quantization.w8a8_int8 import W8A8Int8Config
 
-QUANTIZATION_METHODS: Dict[str, Type[QuantizationConfig]] = {
-    "aqlm": AQLMConfig,
-    "awq": AWQConfig,
-    "deepspeedfp": DeepSpeedFPConfig,
-    "tpu_int8": Int8TpuConfig,
+# Base quantization methods that don't depend on vllm
+BASE_QUANTIZATION_METHODS: Dict[str, Type[QuantizationConfig]] = {
     "fp8": Fp8Config,
     "blockwise_int8": BlockInt8Config,
-    "fbgemm_fp8": FBGEMMFp8Config,
-    "marlin": MarlinConfig,
     "modelopt": ModelOptFp8Config,
-    "gguf": GGUFConfig,
-    "gptq_marlin_24": GPTQMarlin24Config,
     "gptq_marlin": GPTQMarlinConfig,
-    "awq_marlin": AWQMarlinConfig,
     "gptq": GPTQConfig,
-    "compressed-tensors": CompressedTensorsConfig,
-    "bitsandbytes": BitsAndBytesConfig,
-    "qqq": QQQConfig,
-    "experts_int8": ExpertsInt8Config,
     "w8a8_int8": W8A8Int8Config,
     "w8a8_fp8": W8A8Fp8Config,
 }
 
+# Add vllm-dependent methods if available
+QUANTIZATION_METHODS = BASE_QUANTIZATION_METHODS.copy()
+if VLLM_AVAILABLE:
+    VLLM_QUANTIZATION_METHODS = {
+        "aqlm": AQLMConfig,
+        "awq": AWQConfig,
+        "deepspeedfp": DeepSpeedFPConfig,
+        "tpu_int8": Int8TpuConfig,
+        "fbgemm_fp8": FBGEMMFp8Config,
+        "marlin": MarlinConfig,
+        "gguf": GGUFConfig,
+        "gptq_marlin_24": GPTQMarlin24Config,
+        "awq_marlin": AWQMarlinConfig,
+        "compressed-tensors": CompressedTensorsConfig,
+        "bitsandbytes": BitsAndBytesConfig,
+        "qqq": QQQConfig,
+        "experts_int8": ExpertsInt8Config,
+    }
+    QUANTIZATION_METHODS.update(VLLM_QUANTIZATION_METHODS)
+
 
 def get_quantization_config(quantization: str) -> Type[QuantizationConfig]:
     if quantization not in QUANTIZATION_METHODS:
@@ -157,25 +185,31 @@ def get_linear_quant_method(
 
 
 def gptq_get_quant_method(self, layer, prefix):
-    from vllm.model_executor.layers.quantization.gptq import GPTQLinearMethod
-    from vllm.model_executor.layers.quantization.gptq_marlin import (
-        GPTQMarlinLinearMethod,
-        GPTQMarlinMoEMethod,
-    )
+    if not VLLM_AVAILABLE:
+        return None
+
+    try:
+        from vllm.model_executor.layers.quantization.gptq import GPTQLinearMethod
+        from vllm.model_executor.layers.quantization.gptq_marlin import (
+            GPTQMarlinLinearMethod,
+            GPTQMarlinMoEMethod,
+        )
 
-    from sglang.srt.layers.moe.fused_moe_triton.layer import FusedMoE
+        from sglang.srt.layers.moe.fused_moe_triton.layer import FusedMoE
 
-    if isinstance(layer, FusedMoE):
-        return GPTQMarlinMoEMethod(self)
+        if isinstance(layer, FusedMoE):
+            return GPTQMarlinMoEMethod(self)
 
-    if isinstance(self, GPTQConfig):
-        return get_linear_quant_method(
-            self, layer, prefix=prefix, linear_method_cls=GPTQLinearMethod
-        )
-    elif isinstance(self, GPTQMarlinConfig):
-        return get_linear_quant_method(
-            self, layer, prefix=prefix, linear_method_cls=GPTQMarlinLinearMethod
-        )
+        if isinstance(self, GPTQConfig):
+            return get_linear_quant_method(
+                self, layer, prefix=prefix, linear_method_cls=GPTQLinearMethod
+            )
+        elif isinstance(self, GPTQMarlinConfig):
+            return get_linear_quant_method(
+                self, layer, prefix=prefix, linear_method_cls=GPTQMarlinLinearMethod
+            )
+    except ImportError:
+        pass
     return None
 
 
@@ -187,33 +221,40 @@ def monkey_patch_isinstance_for_vllm_base_layer(reverse: bool = False):
     Patch isinstance so that the `get_quant_method` in vllm's QuantizationConfig
     can recognize sglang layers
     """
+    if not VLLM_AVAILABLE:
+        return
 
     if reverse:
         builtins.isinstance = original_isinstance
         return
 
-    from vllm.model_executor.layers.fused_moe import FusedMoE
-    from vllm.model_executor.layers.linear import LinearBase
-    from vllm.model_executor.layers.vocab_parallel_embedding import (
-        VocabParallelEmbedding,
-    )
-
-    from sglang.srt.layers.linear import LinearBase as PatchedLinearBase
-    from sglang.srt.layers.moe.fused_moe_triton.layer import FusedMoE as PatchedFusedMoE
-    from sglang.srt.layers.vocab_parallel_embedding import (
-        VocabParallelEmbedding as PatchedVocabParallelEmbedding,
-    )
+    try:
+        from vllm.model_executor.layers.fused_moe import FusedMoE
+        from vllm.model_executor.layers.linear import LinearBase
+        from vllm.model_executor.layers.vocab_parallel_embedding import (
+            VocabParallelEmbedding,
+        )
 
-    def patched_isinstance(obj, classinfo):
-        if classinfo is LinearBase:
-            return original_isinstance(obj, PatchedLinearBase)
-        if classinfo is FusedMoE:
-            return original_isinstance(obj, PatchedFusedMoE)
-        if classinfo is VocabParallelEmbedding:
-            return original_isinstance(obj, PatchedVocabParallelEmbedding)
-        return original_isinstance(obj, classinfo)
+        from sglang.srt.layers.linear import LinearBase as PatchedLinearBase
+        from sglang.srt.layers.moe.fused_moe_triton.layer import (
+            FusedMoE as PatchedFusedMoE,
+        )
+        from sglang.srt.layers.vocab_parallel_embedding import (
+            VocabParallelEmbedding as PatchedVocabParallelEmbedding,
+        )
 
-    builtins.isinstance = patched_isinstance
+        def patched_isinstance(obj, classinfo):
+            if classinfo is LinearBase:
+                return original_isinstance(obj, PatchedLinearBase)
+            if classinfo is FusedMoE:
+                return original_isinstance(obj, PatchedFusedMoE)
+            if classinfo is VocabParallelEmbedding:
+                return original_isinstance(obj, PatchedVocabParallelEmbedding)
+            return original_isinstance(obj, classinfo)
+
+        builtins.isinstance = patched_isinstance
+    except ImportError:
+        return
 
 
 def monkey_patch_moe_apply(class_obj: "FusedMoEMethodBase"):
@@ -221,72 +262,88 @@ def monkey_patch_moe_apply(class_obj: "FusedMoEMethodBase"):
     Monkey patch the apply function of vllm's FusedMoEMethodBase.
     Convert sglang arguments to vllm arguments.
     """
-    original_apply = class_obj.apply
-    sig = inspect.signature(original_apply)
-    param_names = list(sig.parameters.keys())
-    has_correction_bias = "e_score_correction_bias" in param_names
-
-    def new_apply(
-        self,
-        layer: torch.nn.Module,
-        x: torch.Tensor,
-        router_logits: torch.Tensor,
-        top_k: int,
-        renormalize: bool,
-        use_grouped_topk: bool,
-        topk_group: Optional[int] = None,
-        num_expert_group: Optional[int] = None,
-        custom_routing_function: Optional[Callable] = None,
-        correction_bias: Optional[torch.Tensor] = None,
-        activation: str = "silu",
-        inplace: bool = True,
-        no_combine: bool = False,
-    ):
-        assert activation == "silu"
-        assert inplace and not no_combine
-
-        kwargs = {
-            "self": self,
-            "layer": layer,
-            "x": x,
-            "router_logits": router_logits,
-            "top_k": top_k,
-            "renormalize": renormalize,
-            "use_grouped_topk": use_grouped_topk,
-            "topk_group": topk_group,
-            "num_expert_group": num_expert_group,
-            "custom_routing_function": custom_routing_function,
-        }
-        if correction_bias is not None:
-            if not has_correction_bias:
-                raise ValueError(
-                    "Please increase the version of your vllm. Try `pip install vllm==0.7.2`"
-                )
-            kwargs["e_score_correction_bias"] = correction_bias
-        return original_apply(**kwargs)
-
-    setattr(class_obj, "apply", new_apply)
+    if not VLLM_AVAILABLE:
+        return
+
+    try:
+        original_apply = class_obj.apply
+        sig = inspect.signature(original_apply)
+        param_names = list(sig.parameters.keys())
+        has_correction_bias = "e_score_correction_bias" in param_names
+
+        def new_apply(
+            self,
+            layer: torch.nn.Module,
+            x: torch.Tensor,
+            router_logits: torch.Tensor,
+            top_k: int,
+            renormalize: bool,
+            use_grouped_topk: bool,
+            topk_group: Optional[int] = None,
+            num_expert_group: Optional[int] = None,
+            custom_routing_function: Optional[Callable] = None,
+            correction_bias: Optional[torch.Tensor] = None,
+            activation: str = "silu",
+            inplace: bool = True,
+            no_combine: bool = False,
+        ):
+            assert activation == "silu"
+            assert inplace and not no_combine
+
+            kwargs = {
+                "self": self,
+                "layer": layer,
+                "x": x,
+                "router_logits": router_logits,
+                "top_k": top_k,
+                "renormalize": renormalize,
+                "use_grouped_topk": use_grouped_topk,
+                "topk_group": topk_group,
+                "num_expert_group": num_expert_group,
+                "custom_routing_function": custom_routing_function,
+            }
+            if correction_bias is not None:
+                if not has_correction_bias:
+                    raise ValueError(
+                        "Please increase the version of your vllm. Try `pip install vllm==0.7.2`"
+                    )
+                kwargs["e_score_correction_bias"] = correction_bias
+            return original_apply(**kwargs)
+
+        setattr(class_obj, "apply", new_apply)
+    except (ImportError, AttributeError):
+        return
 
 
 def monkey_patch_quant_configs():
     """Apply all monkey patches in one place."""
-    from vllm.model_executor.layers.quantization.awq_marlin import AWQMoEMethod
-    from vllm.model_executor.layers.quantization.compressed_tensors.compressed_tensors_moe import (
-        CompressedTensorsW8A8Fp8MoEMethod,
-        CompressedTensorsWNA16MoEMethod,
-    )
-    from vllm.model_executor.layers.quantization.gptq_marlin import GPTQMarlinMoEMethod
+    if not VLLM_AVAILABLE:
+        return
 
-    setattr(GPTQMarlinConfig, "get_quant_method", gptq_get_quant_method)
-    setattr(GPTQConfig, "get_quant_method", gptq_get_quant_method)
+    try:
+        from vllm.model_executor.layers.quantization.awq_marlin import AWQMoEMethod
+        from vllm.model_executor.layers.quantization.compressed_tensors.compressed_tensors_moe import (
+            CompressedTensorsW8A8Fp8MoEMethod,
+            CompressedTensorsWNA16MoEMethod,
+        )
+        from vllm.model_executor.layers.quantization.gptq_marlin import (
+            GPTQMarlinMoEMethod,
+        )
+
+        setattr(GPTQMarlinConfig, "get_quant_method", gptq_get_quant_method)
+        setattr(GPTQConfig, "get_quant_method", gptq_get_quant_method)
 
-    monkey_patch_moe_apply(AWQMoEMethod)
-    monkey_patch_moe_apply(GPTQMarlinMoEMethod)
-    monkey_patch_moe_apply(CompressedTensorsW8A8Fp8MoEMethod)
-    monkey_patch_moe_apply(CompressedTensorsWNA16MoEMethod)
+        monkey_patch_moe_apply(AWQMoEMethod)
+        monkey_patch_moe_apply(GPTQMarlinMoEMethod)
+        monkey_patch_moe_apply(CompressedTensorsW8A8Fp8MoEMethod)
+        monkey_patch_moe_apply(CompressedTensorsWNA16MoEMethod)
+    except ImportError:
+        return
 
 
-monkey_patch_quant_configs()
+# Only apply monkey patches if vllm is available
+if VLLM_AVAILABLE:
+    monkey_patch_quant_configs()
 
 
 __all__ = [

python/sglang/srt/layers/quantization/blockwise_int8.py

@@ -5,7 +5,6 @@ from typing import Any, Callable, Dict, List, Optional
 
 import torch
 from torch.nn import Module
-from vllm.model_executor.layers.quantization.utils.quant_utils import is_layer_skipped
 
 from sglang.srt.distributed import get_tensor_model_parallel_world_size
 from sglang.srt.layers.linear import (
@@ -19,6 +18,7 @@ from sglang.srt.layers.quantization.base_config import (
     QuantizeMethodBase,
 )
 from sglang.srt.layers.quantization.int8_utils import apply_w8a8_block_int8_linear
+from sglang.srt.layers.quantization.utils import is_layer_skipped
 from sglang.srt.utils import set_weight_attrs
 
 ACTIVATION_SCHEMES = ["static", "dynamic"]

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

@@ -7,20 +7,33 @@ import torch
 import torch.nn.functional as F
 from torch.nn import Module
 from torch.nn.parameter import Parameter
-from vllm import _custom_ops as ops
-from vllm.model_executor.layers.quantization.kv_cache import BaseKVCacheMethod
-from vllm.model_executor.layers.quantization.utils.marlin_utils_fp8 import (
-    apply_fp8_marlin_linear,
-    prepare_fp8_layer_for_marlin,
-)
-from vllm.model_executor.layers.quantization.utils.quant_utils import is_layer_skipped
-from vllm.model_executor.layers.quantization.utils.w8a8_utils import (
+
+from sglang.srt.layers.quantization.kv_cache import BaseKVCacheMethod
+from sglang.srt.layers.quantization.utils import (
     all_close_1d,
     convert_to_channelwise,
+    is_layer_skipped,
     per_tensor_dequantize,
     requantize_with_max_scale,
 )
 
+try:
+    from vllm.model_executor.layers.quantization.utils.marlin_utils_fp8 import (
+        apply_fp8_marlin_linear,
+        prepare_fp8_layer_for_marlin,
+    )
+
+    MARLIN_FP8_AVAILABLE = True
+except ImportError:
+    MARLIN_FP8_AVAILABLE = False
+
+    def apply_fp8_marlin_linear(*args, **kwargs):
+        raise ImportError("vllm is not installed")
+
+    def prepare_fp8_layer_for_marlin(*args, **kwargs):
+        raise ImportError("vllm is not installed")
+
+
 from sglang.srt.distributed import get_tensor_model_parallel_world_size
 from sglang.srt.layers.linear import (
     LinearBase,
@@ -46,6 +59,7 @@ from sglang.srt.layers.quantization.fp8_utils import (
 )
 from sglang.srt.utils import (
     get_bool_env_var,
+    is_cuda,
     is_hip,
     permute_weight,
     print_warning_once,
@@ -60,6 +74,13 @@ if _is_hip:
     from aiter.fused_moe_bf16_asm import asm_moe
     from aiter.ops.shuffle import shuffle_weight
 
+_is_cuda = is_cuda()
+
+if _is_cuda:
+    from sglang.srt.custom_op import scaled_fp8_quant as sgl_scaled_fp8_quant
+else:
+    from vllm import _custom_ops as vllm_ops
+
 logger = logging.getLogger(__name__)
 
 
@@ -173,7 +194,9 @@ class Fp8LinearMethod(LinearMethodBase):
 
         # For GPUs that lack FP8 hardware support, we can leverage the Marlin
         # kernel for fast weight-only FP8 quantization
-        self.use_marlin = get_bool_env_var("SGLANG_FORCE_FP8_MARLIN")
+        self.use_marlin = (
+            get_bool_env_var("SGLANG_FORCE_FP8_MARLIN") and MARLIN_FP8_AVAILABLE
+        )
         # Disable marlin for ROCm
         if _is_hip:
             self.use_marlin = False
@@ -371,9 +394,12 @@ class Fp8LinearMethod(LinearMethodBase):
                 )
 
         if self.use_marlin:
-            prepare_fp8_layer_for_marlin(layer)
-            # Activations not quantized for marlin.
-            del layer.input_scale
+            try:
+                prepare_fp8_layer_for_marlin(layer)
+                # Activations not quantized for marlin.
+                del layer.input_scale
+            except ImportError:
+                self.use_marlin = False
 
     def apply(
         self,
@@ -383,15 +409,18 @@ class Fp8LinearMethod(LinearMethodBase):
     ) -> torch.Tensor:
 
         if self.use_marlin:
-            return apply_fp8_marlin_linear(
-                input=x,
-                weight=layer.weight,
-                weight_scale=layer.weight_scale,
-                workspace=layer.workspace,
-                size_n=layer.output_size_per_partition,
-                size_k=layer.input_size_per_partition,
-                bias=bias,
-            )
+            try:
+                return apply_fp8_marlin_linear(
+                    input=x,
+                    weight=layer.weight,
+                    weight_scale=layer.weight_scale,
+                    workspace=layer.workspace,
+                    size_n=layer.output_size_per_partition,
+                    size_k=layer.input_size_per_partition,
+                    bias=bias,
+                )
+            except ImportError:
+                self.use_marlin = False
 
         if self.block_quant:
             return apply_w8a8_block_fp8_linear(
@@ -680,12 +709,20 @@ class Fp8MoEMethod:
                 requires_grad=False,
             )
             for expert in range(layer.num_experts):
-                w13_weight[expert, :, :], layer.w13_weight_scale[expert] = (
-                    ops.scaled_fp8_quant(layer.w13_weight.data[expert, :, :])
-                )
-                w2_weight[expert, :, :], layer.w2_weight_scale[expert] = (
-                    ops.scaled_fp8_quant(layer.w2_weight.data[expert, :, :])
-                )
+                if _is_cuda:
+                    w13_weight[expert, :, :], layer.w13_weight_scale[expert] = (
+                        sgl_scaled_fp8_quant(layer.w13_weight.data[expert, :, :])
+                    )
+                    w2_weight[expert, :, :], layer.w2_weight_scale[expert] = (
+                        sgl_scaled_fp8_quant(layer.w2_weight.data[expert, :, :])
+                    )
+                else:
+                    w13_weight[expert, :, :], layer.w13_weight_scale[expert] = (
+                        vllm_ops.scaled_fp8_quant(layer.w13_weight.data[expert, :, :])
+                    )
+                    w2_weight[expert, :, :], layer.w2_weight_scale[expert] = (
+                        vllm_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)
 

python/sglang/srt/layers/quantization/fp8_utils.py

@@ -28,7 +28,12 @@ if _is_cuda:
     from sglang.srt.layers.quantization.fp8_kernel import sglang_per_token_quant_fp8
 
     if use_vllm_cutlass_w8a8_fp8_kernel:
-        from vllm import _custom_ops as ops
+        try:
+            from vllm import _custom_ops as ops
+
+            VLLM_AVAILABLE = True
+        except ImportError:
+            VLLM_AVAILABLE = False
     else:
         from sgl_kernel import fp8_scaled_mm
 
@@ -219,90 +224,97 @@ def apply_fp8_linear(
             )
 
     if cutlass_fp8_supported:
-        if use_vllm_cutlass_w8a8_fp8_kernel:
-            # Fall back to vllm cutlass w8a8 fp8 kernel
-            output = ops.cutlass_scaled_mm(
-                qinput,
-                weight,
-                out_dtype=input.dtype,
-                scale_a=x_scale,
-                scale_b=weight_scale,
-                bias=bias,
-            )
-        else:
-            assert (
-                weight_scale.numel() == weight.shape[1]
-            ), "cutlass w8a8 fp8 sgl-kernel only supports per-channel scale"
-            output = fp8_scaled_mm(
-                qinput, weight, x_scale, weight_scale, out_dtype=input.dtype, bias=bias
-            )
-        return output.view(*output_shape)
+        try:
+            if VLLM_AVAILABLE and use_vllm_cutlass_w8a8_fp8_kernel:
+                # Fall back to vllm cutlass w8a8 fp8 kernel
+                output = ops.cutlass_scaled_mm(
+                    qinput,
+                    weight,
+                    out_dtype=input.dtype,
+                    scale_a=x_scale,
+                    scale_b=weight_scale,
+                    bias=bias,
+                )
+            else:
+                assert (
+                    weight_scale.numel() == weight.shape[1]
+                ), "cutlass w8a8 fp8 sgl-kernel only supports per-channel scale"
+                output = fp8_scaled_mm(
+                    qinput,
+                    weight,
+                    x_scale,
+                    weight_scale,
+                    out_dtype=input.dtype,
+                    bias=bias,
+                )
+            return output.view(*output_shape)
+        except (ImportError, NameError, AttributeError):
+            pass
 
     # torch.scaled_mm supports per tensor weights + activations only
     # so fallback to naive if per channel or per token
-    else:
-        per_tensor_weights = weight_scale.numel() == 1
-        per_tensor_activations = x_scale.numel() == 1
-
-        if per_tensor_weights and per_tensor_activations:
-            # Fused GEMM_DQ
-            output = torch._scaled_mm(
-                qinput,
-                weight,
-                out_dtype=input.dtype,
-                scale_a=x_scale,
-                scale_b=weight_scale,
-                bias=bias,
-            )
-            # A fix for discrepancy in scaled_mm which returns tuple
-            # for torch < 2.5 and a single value in torch >= 2.5
-            if type(output) is tuple and len(output) == 2:
-                output = output[0]
+    per_tensor_weights = weight_scale.numel() == 1
+    per_tensor_activations = x_scale.numel() == 1
+
+    if per_tensor_weights and per_tensor_activations:
+        # Fused GEMM_DQ
+        output = torch._scaled_mm(
+            qinput,
+            weight,
+            out_dtype=input.dtype,
+            scale_a=x_scale,
+            scale_b=weight_scale,
+            bias=bias,
+        )
+        # A fix for discrepancy in scaled_mm which returns tuple
+        # for torch < 2.5 and a single value in torch >= 2.5
+        if type(output) is tuple and len(output) == 2:
+            output = output[0]
 
-            return torch.narrow(output, 0, 0, input_2d.shape[0]).view(*output_shape)
+        return torch.narrow(output, 0, 0, input_2d.shape[0]).view(*output_shape)
 
-        else:
-            # Fallback for channelwise case, where we use unfused DQ
-            # due to limitations with scaled_mm
-
-            # Symmetric quantized GEMM by definition computes the following:
-            #   C = (s_x * X) (s_w * W) + bias
-            # This is equivalent to dequantizing the weights and activations
-            # before applying a GEMM.
-            #
-            # In order to compute quantized operands, a quantized kernel
-            # will rewrite the above like so:
-            #   C = s_w * s_x * (X * W) + bias
-            #
-            # For the scaled_mm fallback case, we break this down, since it
-            # does not support s_w being a vector.
-
-            # Making sure the dummy tensor is on the same device as the weight
-            global TORCH_DEVICE_IDENTITY
-            if TORCH_DEVICE_IDENTITY.device != weight.device:
-                TORCH_DEVICE_IDENTITY = TORCH_DEVICE_IDENTITY.to(weight.device)
-
-            # GEMM
-            # This computes C = (X * W).
-            # Output in fp32 to allow subsequent ops to happen in-place
-            output = torch._scaled_mm(
-                qinput,
-                weight,
-                scale_a=TORCH_DEVICE_IDENTITY,
-                scale_b=TORCH_DEVICE_IDENTITY,
-                out_dtype=torch.float32,
-            )
-            # A fix for discrepancy in scaled_mm which returns tuple
-            # for torch < 2.5 and a single value in torch >= 2.5
-            if type(output) is tuple and len(output) == 2:
-                output = output[0]
-            # Unpad (undo num_token_padding)
-            output = torch.narrow(output, 0, 0, input_2d.shape[0])
-            x_scale = torch.narrow(x_scale, 0, 0, input_2d.shape[0])
-
-            # DQ
-            # C = sw * sx * (X * W) + bias
-            output = output * x_scale * weight_scale.t()
-            if bias is not None:
-                output = output + bias
-            return output.to(dtype=input.dtype).view(*output_shape)
+    else:
+        # Fallback for channelwise case, where we use unfused DQ
+        # due to limitations with scaled_mm
+
+        # Symmetric quantized GEMM by definition computes the following:
+        #   C = (s_x * X) (s_w * W) + bias
+        # This is equivalent to dequantizing the weights and activations
+        # before applying a GEMM.
+        #
+        # In order to compute quantized operands, a quantized kernel
+        # will rewrite the above like so:
+        #   C = s_w * s_x * (X * W) + bias
+        #
+        # For the scaled_mm fallback case, we break this down, since it
+        # does not support s_w being a vector.
+
+        # Making sure the dummy tensor is on the same device as the weight
+        global TORCH_DEVICE_IDENTITY
+        if TORCH_DEVICE_IDENTITY.device != weight.device:
+            TORCH_DEVICE_IDENTITY = TORCH_DEVICE_IDENTITY.to(weight.device)
+
+        # GEMM
+        # This computes C = (X * W).
+        # Output in fp32 to allow subsequent ops to happen in-place
+        output = torch._scaled_mm(
+            qinput,
+            weight,
+            scale_a=TORCH_DEVICE_IDENTITY,
+            scale_b=TORCH_DEVICE_IDENTITY,
+            out_dtype=torch.float32,
+        )
+        # A fix for discrepancy in scaled_mm which returns tuple
+        # for torch < 2.5 and a single value in torch >= 2.5
+        if type(output) is tuple and len(output) == 2:
+            output = output[0]
+        # Unpad (undo num_token_padding)
+        output = torch.narrow(output, 0, 0, input_2d.shape[0])
+        x_scale = torch.narrow(x_scale, 0, 0, input_2d.shape[0])
+
+        # DQ
+        # C = sw * sx * (X * W) + bias
+        output = output * x_scale * weight_scale.t()
+        if bias is not None:
+            output = output + bias
+        return output.to(dtype=input.dtype).view(*output_shape)

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

@@ -3,11 +3,21 @@ from fractions import Fraction
 from typing import Any, Dict, List, Optional, Union
 
 import torch
-from vllm.scalar_type import scalar_types
 
 from sglang.srt.layers.linear import LinearBase
 from sglang.srt.layers.quantization.base_config import QuantizationConfig
+from sglang.srt.layers.quantization.utils import scalar_types
 from sglang.srt.layers.vocab_parallel_embedding import ParallelLMHead
+from sglang.srt.utils import is_cuda
+
+_is_cuda = is_cuda()
+
+try:
+    import vllm
+
+    VLLM_AVAILABLE = True
+except ImportError:
+    VLLM_AVAILABLE = False
 
 logger = logging.getLogger(__name__)
 
@@ -110,6 +120,9 @@ class GPTQConfig(QuantizationConfig):
     def get_quant_method(
         self, layer: torch.nn.Module, prefix: str
     ) -> Optional["GPTQLinearMethod"]:
+        if not VLLM_AVAILABLE:
+            raise ImportError("vllm is not installed")
+
         from vllm.model_executor.layers.quantization.gptq import GPTQLinearMethod
 
         from sglang.srt.layers.quantization import get_linear_quant_method
@@ -263,6 +276,9 @@ class GPTQMarlinConfig(QuantizationConfig):
     def get_quant_method(
         self, layer: torch.nn.Module, prefix: str
     ) -> Optional["QuantizeMethodBase"]:
+        if not VLLM_AVAILABLE:
+            raise ImportError("vllm is not installed")
+
         from vllm.model_executor.layers.quantization.gptq_marlin import (
             GPTQMarlinLinearMethod,
             GPTQMarlinMoEMethod,
@@ -285,6 +301,9 @@ class GPTQMarlinConfig(QuantizationConfig):
 
     @classmethod
     def is_gptq_marlin_compatible(cls, quant_config: Dict[str, Any]):
+        if not VLLM_AVAILABLE:
+            return False
+
         quant_method = quant_config.get("quant_method", "").lower()
         num_bits = quant_config.get("bits")
         group_size = quant_config.get("group_size")
@@ -294,9 +313,8 @@ class GPTQMarlinConfig(QuantizationConfig):
         from vllm.model_executor.layers.quantization.utils.marlin_utils import (
             check_marlin_supported,
         )
-        from vllm.platforms import current_platform
 
-        if not current_platform.is_cuda():
+        if not _is_cuda:
             return False
 
         if quant_method != "gptq":
@@ -407,6 +425,9 @@ class MarlinConfig(QuantizationConfig):
     def get_quant_method(
         self, layer: torch.nn.Module, prefix: str
     ) -> Optional["MarlinLinearMethod"]:
+        if not VLLM_AVAILABLE:
+            raise ImportError("vllm is not installed")
+
         from vllm.model_executor.layers.quantization.marlin import MarlinLinearMethod
 
         if isinstance(layer, LinearBase) or (

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

+# Adapted from https://github.com/vllm-project/vllm/blob/main/vllm/model_executor/layers/quantization/kv_cache.py
+
+import logging
+
+import torch
+
+from sglang.srt.layers.quantization.base_config import (
+    QuantizationConfig,
+    QuantizeMethodBase,
+)
+from sglang.srt.utils import is_hip
+
+_is_hip = is_hip()
+
+logger = logging.getLogger(__name__)
+
+
+class BaseKVCacheMethod(QuantizeMethodBase):
+    """
+    Quant method that adds `_k_scale` and `_v_scale` attributes to the
+    Attention layer to support loading those scaling factors from checkpoints.
+    The k/v_scale will be used to:
+        - quantize k/v_cache entries before saving them to the cache
+        - dequantize k/v_cache entries before fetching them from the cache
+
+    :param quant_config: the appropriate QuantizationConfig
+    """
+
+    def __init__(self, quant_config: QuantizationConfig):
+        self.quant_config = quant_config
+
+    def create_weights(self, layer: torch.nn.Module):
+        """
+        Create "weight" (aka k_scale and v_scale) for an attention layer.
+        """
+        # Initialize the KV cache scales to -1.0, which is an invalid value.
+        # If the k/v_scale appears in the checkpoint, it will be
+        # overwritten when loading weights.
+        layer.k_scale = torch.nn.Parameter(torch.tensor(-1.0), requires_grad=False)
+        layer.v_scale = torch.nn.Parameter(torch.tensor(-1.0), requires_grad=False)
+
+    @classmethod
+    def is_fp8_fnuz(cls) -> bool:
+        # only device 0 is checked, this assumes MI300 platforms are homogeneous
+        return "gfx94" in torch.cuda.get_device_properties(0).gcnArchName
+
+    def apply(self, layer: torch.nn.Module) -> torch.Tensor:
+        raise RuntimeError(f"{self.__class__.__name__}.apply should not be called.")
+
+    def process_weights_after_loading(self, layer: torch.nn.Module) -> None:
+        # If the kv-cache dtype is auto, we enforce the k/v_scale to be 1.0
+        # regardless whether the kv-scale is available in the checkpoint.
+        # No need to process kv scales after loading if we are going to
+        # calculate them on the fly.
+        if layer.kv_cache_dtype != "auto" and not layer.calculate_kv_scales:
+            if layer.k_scale > 0.0 and layer.v_scale > 0.0:
+                # We prefer to use separate k_scale and v_scale if present
+                k_scale = layer.k_scale.to("cpu").tolist()
+                v_scale = layer.v_scale.to("cpu").tolist()
+                if _is_hip and self.is_fp8_fnuz():
+                    k_scale *= 2
+                    v_scale *= 2
+            elif layer.k_scale < 0.0 and layer.v_scale < 0.0:
+                # If no scales were loaded (both scales are invalid negative
+                # values), use the default value of 1.0
+                k_scale = 1.0
+                v_scale = 1.0
+            else:
+                # If we find a single kv_scale in the checkpoint, we remap
+                # kv_scale to k_scale during weight loading, and duplicate
+                # k_scale to v_scale here
+                assert layer.k_scale > 0.0
+                scale_to_duplicate = max(layer.k_scale, layer.v_scale)
+                k_scale = scale_to_duplicate.to("cpu").tolist()
+                v_scale = scale_to_duplicate.to("cpu").tolist()
+                if _is_hip and self.is_fp8_fnuz():
+                    k_scale *= 2
+                    v_scale *= 2
+
+            if not isinstance(k_scale, float) or not isinstance(v_scale, float):
+                raise ValueError(
+                    "Only support per-tensor scaling factor " "for fp8 KV cache"
+                )
+
+            # These are used in the final Attention.forward()
+            layer._k_scale.copy_(k_scale)
+            layer._v_scale.copy_(v_scale)
+            layer._k_scale_float = k_scale
+            layer._v_scale_float = v_scale
+            if k_scale == 1.0 and v_scale == 1.0 and "e5m2" not in layer.kv_cache_dtype:
+                logger.warning(
+                    "Using KV cache scaling factor 1.0 for fp8_e4m3. This "
+                    "may cause accuracy issues. Please make sure k/v_scale "
+                    "scaling factors are available in the fp8 checkpoint."
+                )
+
+        del layer.k_scale
+        del layer.v_scale

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

@@ -5,12 +5,6 @@ from typing import Any, Dict, List, Optional
 
 import torch
 from torch.nn.parameter import Parameter
-from vllm.model_executor.layers.quantization.kv_cache import BaseKVCacheMethod
-from vllm.model_executor.layers.quantization.utils.w8a8_utils import (
-    convert_to_channelwise,
-    cutlass_fp8_supported,
-    requantize_with_max_scale,
-)
 
 from sglang.srt.layers.attention.base_attn_backend import AttentionBackend
 from sglang.srt.layers.linear import LinearBase, LinearMethodBase
@@ -19,7 +13,15 @@ from sglang.srt.layers.quantization.base_config import (
     QuantizationConfig,
     QuantizeMethodBase,
 )
-from sglang.srt.layers.quantization.fp8_utils import apply_fp8_linear
+from sglang.srt.layers.quantization.fp8_utils import (
+    apply_fp8_linear,
+    cutlass_fp8_supported,
+)
+from sglang.srt.layers.quantization.kv_cache import BaseKVCacheMethod
+from sglang.srt.layers.quantization.utils import (
+    convert_to_channelwise,
+    requantize_with_max_scale,
+)
 
 # Initialize logger for the module
 logger = logging.getLogger(__name__)

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

+# Adapted from https://github.com/vllm-project/vllm/blob/main/vllm/model_executor/layers/quantization/utils/quant_utils.py
+# Adapted from https://github.com/vllm-project/vllm/blob/main/vllm/scalar_type.py
+
+import functools
+import struct
+from dataclasses import dataclass
+from enum import Enum
+from types import MappingProxyType
+from typing import List, Mapping, Optional, Tuple, Union
+
+import torch
+
+
+def is_layer_skipped(
+    prefix: str,
+    ignored_layers: List[str],
+    fused_mapping: Mapping[str, List[str]] = MappingProxyType({}),
+) -> bool:
+    # prefix: model.layers.0.self_attn.q_proj
+    # proj_name: q_proj
+    proj_name = prefix.split(".")[-1]
+
+    # Fused layers like gate_up_proj or qkv_proj will not be fused
+    # in the safetensors checkpoint. So, we convert the name
+    # from the fused version to unfused + check to make sure that
+    # each shard of the fused layer has the same scheme.
+    if proj_name in fused_mapping:
+        shard_prefixes = [
+            prefix.replace(proj_name, shard_proj_name)
+            for shard_proj_name in fused_mapping[proj_name]
+        ]
+
+        is_skipped = None
+        for shard_prefix in shard_prefixes:
+            is_shard_skipped = shard_prefix in ignored_layers
+
+            if is_skipped is None:
+                is_skipped = is_shard_skipped
+            elif is_shard_skipped != is_skipped:
+                raise ValueError(
+                    f"Detected some but not all shards of {prefix} "
+                    "are quantized. All shards of fused layers "
+                    "to have the same precision."
+                )
+    else:
+        is_skipped = prefix in ignored_layers
+
+    assert is_skipped is not None
+    return is_skipped
+
+
+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]))
+
+
+def convert_to_channelwise(
+    weight_scale: torch.Tensor, logical_widths: List[int]
+) -> Tuple[torch.Tensor, torch.Tensor]:
+    # Create channelwise buffer
+    weight_scale_channel = torch.empty(
+        (sum(logical_widths), 1), dtype=torch.float32, device=weight_scale.device
+    )
+
+    # Expand each scale to match the size of each logical matrix.
+    start = 0
+    for idx, logical_width in enumerate(logical_widths):
+        end = start + logical_width
+        weight_scale_channel[start:end, :] = weight_scale[idx]
+        start = end
+
+    return weight_scale_channel
+
+
+def requantize_with_max_scale(
+    weight: torch.Tensor, weight_scale: torch.Tensor, logical_widths: List[int]
+) -> Tuple[torch.Tensor, torch.Tensor]:
+    # Max scale to be used for requanitzation.
+    max_w_scale = 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. Skip requantization in this case (since)
+    # we already are quantized with the single scale.
+    # * Sample Model: nm-testing/Phi-3-mini-128k-instruct-FP8
+    unfused_module_in_checkpoint = (
+        weight_scale[-1] > torch.finfo(torch.float8_e4m3fn).min
+    )
+
+    # If unfused checkpoint, need requanize with the single scale.
+    if unfused_module_in_checkpoint:
+        start = 0
+        for idx, logical_width in enumerate(logical_widths):
+            end = start + logical_width
+            weight_dq = per_tensor_dequantize(weight[start:end, :], weight_scale[idx])
+            weight[start:end, :], _ = ops.scaled_fp8_quant(weight_dq, max_w_scale)
+            start = end
+
+    return max_w_scale, weight
+
+
+# Mirrors enum in `core/scalar_type.hpp`
+class NanRepr(Enum):
+    NONE = 0  # nans are not supported
+    IEEE_754 = 1  # nans are: Exp all 1s, mantissa not all 0s
+    EXTD_RANGE_MAX_MIN = 2  # nans are: Exp all 1s, mantissa all 1s
+
+
+# This ScalarType class is a parallel implementation of the C++ ScalarType
+# class found in csrc/core/scalar_type.hpp.  These two classes should be kept
+# in sync until the inductor fully supports custom C++ classes.
+@dataclass(frozen=True)
+class ScalarType:
+    """
+    ScalarType can represent a wide range of floating point and integer
+    types, in particular it can be used to represent sub-byte data types
+    (something that torch.dtype currently does not support). It is also
+    capable of  representing types with a bias, i.e.:
+      `stored_value = value + bias`,
+    this is useful for quantized types (e.g. standard GPTQ 4bit uses a bias
+    of 8). The implementation for this class can be found in
+    csrc/core/scalar_type.hpp, these type signatures should be kept in sync
+    with that file.
+    """
+
+    exponent: int
+    """
+    Number of bits in the exponent if this is a floating point type
+    (zero if this an integer type)
+    """
+
+    mantissa: int
+    """
+    Number of bits in the mantissa if this is a floating point type,
+    or the number bits representing an integer excluding the sign bit if
+    this an integer type.
+    """
+
+    signed: bool
+    "If the type is signed (i.e. has a sign bit)"
+
+    bias: int
+    """
+    bias used to encode the values in this scalar type
+    (value = stored_value - bias, default 0) for example if we store the
+    type as an unsigned integer with a bias of 128 then the value 0 will be
+    stored as 128 and -1 will be stored as 127 and 1 will be stored as 129.
+    """
+
+    _finite_values_only: bool = False
+    """
+    Private: if infs are supported, used `has_infs()` instead.
+    """
+
+    nan_repr: NanRepr = NanRepr.IEEE_754
+    """
+    How NaNs are represent in this scalar type, returns NanRepr value.
+    (not applicable for integer types)
+    """
+
+    def _floating_point_max_int(self) -> int:
+        assert (
+            self.mantissa <= 52 and self.exponent <= 11
+        ), f"Cannot represent max/min as a double for type {self.__str__()}"
+
+        max_mantissa = (1 << self.mantissa) - 1
+        if self.nan_repr == NanRepr.EXTD_RANGE_MAX_MIN:
+            max_mantissa = max_mantissa - 1
+
+        max_exponent = (1 << self.exponent) - 2
+        if self.nan_repr == NanRepr.EXTD_RANGE_MAX_MIN or self.nan_repr == NanRepr.NONE:
+            assert (
+                self.exponent < 11
+            ), f"Cannot represent max/min as a double for type {self.__str__()}"
+            max_exponent = max_exponent + 1
+
+        # adjust the exponent to match that of a double
+        # for now we assume the exponent bias is the standard 2^(e-1) -1, (where
+        # e is the exponent bits), there is some precedent for non-standard
+        # biases, example `float8_e4m3b11fnuz` here:
+        # https://github.com/jax-ml/ml_dtypes but to avoid premature over
+        # complication we are just assuming the standard exponent bias until
+        # there is a need to support non-standard biases
+        exponent_bias = (1 << (self.exponent - 1)) - 1
+        exponent_bias_double = (1 << 10) - 1  # double e = 11
+
+        max_exponent_double = max_exponent - exponent_bias + exponent_bias_double
+
+        # shift the mantissa and exponent into the proper positions for an
+        # IEEE double and bitwise-or them together.
+        return (max_mantissa << (52 - self.mantissa)) | (max_exponent_double << 52)
+
+    def _floating_point_max(self) -> float:
+        double_raw = self._floating_point_max_int()
+        return struct.unpack("!d", struct.pack("!Q", double_raw))[0]
+
+    def _raw_max(self) -> Union[int, float]:
+        if self.is_floating_point():
+            return self._floating_point_max()
+        else:
+            assert (
+                self.size_bits < 64 or self.size_bits == 64 and self.is_signed()
+            ), "Cannot represent max as an int"
+            return (1 << self.mantissa) - 1
+
+    def _raw_min(self) -> Union[int, float]:
+        if self.is_floating_point():
+            assert (
+                self.is_signed()
+            ), "We currently assume all floating point types are signed"
+            sign_bit_double = 1 << 63
+
+            max_raw = self._floating_point_max_int()
+            min_raw = max_raw | sign_bit_double
+            return struct.unpack("!d", struct.pack("!Q", min_raw))[0]
+        else:
+            assert (
+                not self.is_signed() or self.size_bits <= 64
+            ), "Cannot represent min as a int64_t"
+
+            if self.is_signed():
+                return -(1 << (self.size_bits - 1))
+            else:
+                return 0
+
+    @functools.cached_property
+    def id(self) -> int:
+        """
+        Convert the ScalarType to an int which can be passed to pytorch custom
+        ops. This layout of the int must be kept in sync with the C++
+        ScalarType's from_id method.
+        """
+        val = 0
+        offset = 0
+
+        def or_and_advance(member, bit_width):
+            nonlocal val
+            nonlocal offset
+            bit_mask = (1 << bit_width) - 1
+            val = val | (int(member) & bit_mask) << offset
+            offset = offset + bit_width
+
+        or_and_advance(self.exponent, 8)
+        or_and_advance(self.mantissa, 8)
+        or_and_advance(self.signed, 1)
+        or_and_advance(self.bias, 32)
+        or_and_advance(self._finite_values_only, 1)
+        or_and_advance(self.nan_repr.value, 8)
+
+        assert offset <= 64, f"ScalarType fields too big {offset} to fit into an int64"
+
+        return val
+
+    @property
+    def size_bits(self) -> int:
+        return self.exponent + self.mantissa + int(self.signed)
+
+    def min(self) -> Union[int, float]:
+        """
+        Min representable value for this scalar type.
+        (accounting for bias if there is one)
+        """
+        return self._raw_min() - self.bias
+
+    def max(self) -> Union[int, float]:
+        """
+        Max representable value for this scalar type.
+        (accounting for bias if there is one)
+        """
+        return self._raw_max() - self.bias
+
+    def is_signed(self) -> bool:
+        """
+        If the type is signed (i.e. has a sign bit), same as `signed`
+        added for consistency with:
+        https://pytorch.org/docs/stable/generated/torch.Tensor.is_signed.html
+        """
+        return self.signed
+
+    def is_floating_point(self) -> bool:
+        "If the type is a floating point type"
+        return self.exponent != 0
+
+    def is_integer(self) -> bool:
+        "If the type is an integer type"
+        return self.exponent == 0
+
+    def has_bias(self) -> bool:
+        "If the type has a non-zero bias"
+        return self.bias != 0
+
+    def has_infs(self) -> bool:
+        "If the type is floating point and supports infinity"
+        return not self._finite_values_only
+
+    def has_nans(self) -> bool:
+        return self.nan_repr != NanRepr.NONE.value
+
+    def is_ieee_754(self) -> bool:
+        """
+        If the type is a floating point type that follows IEEE 754
+        conventions
+        """
+        return self.nan_repr == NanRepr.IEEE_754.value and not self._finite_values_only
+
+    def __str__(self) -> str:
+        """
+        naming generally follows: https://github.com/jax-ml/ml_dtypes
+        for floating point types (leading f) the scheme is:
+        `float<size_bits>_e<exponent_bits>m<mantissa_bits>[flags]`
+        flags:
+          - no-flags: means it follows IEEE 754 conventions
+          - f: means finite values only (no infinities)
+          - n: means nans are supported (non-standard encoding)
+        for integer types the scheme is:
+          `[u]int<size_bits>[b<bias>]`
+          - if bias is not present it means its zero
+        """
+        if self.is_floating_point():
+            ret = (
+                "float"
+                + str(self.size_bits)
+                + "_e"
+                + str(self.exponent)
+                + "m"
+                + str(self.mantissa)
+            )
+
+            if not self.is_ieee_754():
+                if self._finite_values_only:
+                    ret = ret + "f"
+                if self.nan_repr != NanRepr.NONE:
+                    ret = ret + "n"
+
+            return ret
+        else:
+            ret = ("int" if self.is_signed() else "uint") + str(self.size_bits)
+            if self.has_bias():
+                ret = ret + "b" + str(self.bias)
+            return ret
+
+    def __repr__(self) -> str:
+        return "ScalarType." + self.__str__()
+
+    # __len__ needs to be defined (and has to throw TypeError) for pytorch's
+    # opcheck to work.
+    def __len__(self) -> int:
+        raise TypeError
+
+    #
+    # Convenience Constructors
+    #
+
+    @classmethod
+    def int_(cls, size_bits: int, bias: Optional[int]) -> "ScalarType":
+        "Create a signed integer scalar type (size_bits includes sign-bit)."
+        ret = cls(0, size_bits - 1, True, bias if bias else 0)
+        ret.id  # noqa B018: make sure the id is cached
+        return ret
+
+    @classmethod
+    def uint(cls, size_bits: int, bias: Optional[int]) -> "ScalarType":
+        """Create a unsigned integer scalar type."""
+        ret = cls(0, size_bits, False, bias if bias else 0)
+        ret.id  # noqa B018: make sure the id is cached
+        return ret
+
+    @classmethod
+    def float_IEEE754(cls, exponent: int, mantissa: int) -> "ScalarType":
+        """
+        Create a standard floating point type
+        (i.e. follows IEEE 754 conventions).
+        """
+        assert mantissa > 0 and exponent > 0
+        ret = cls(exponent, mantissa, True, 0)
+        ret.id  # noqa B018: make sure the id is cached
+        return ret
+
+    @classmethod
+    def float_(
+        cls, exponent: int, mantissa: int, finite_values_only: bool, nan_repr: NanRepr
+    ) -> "ScalarType":
+        """
+        Create a non-standard floating point type
+        (i.e. does not follow IEEE 754 conventions).
+        """
+        assert mantissa > 0 and exponent > 0
+        assert nan_repr != NanRepr.IEEE_754, (
+            "use `float_IEEE754` constructor for floating point types that "
+            "follow IEEE 754 conventions"
+        )
+        ret = cls(exponent, mantissa, True, 0, finite_values_only, nan_repr)
+        ret.id  # noqa B018: make sure the id is cached
+        return ret
+
+
+# naming generally follows: https://github.com/jax-ml/ml_dtypes
+# for floating point types (leading f) the scheme is:
+#  `float<size_bits>_e<exponent_bits>m<mantissa_bits>[flags]`
+#  flags:
+#  - no-flags: means it follows IEEE 754 conventions
+#  - f: means finite values only (no infinities)
+#  - n: means nans are supported (non-standard encoding)
+# for integer types the scheme is:
+#  `[u]int<size_bits>[b<bias>]`
+#  - if bias is not present it means its zero
+
+
+class scalar_types:
+    int4 = ScalarType.int_(4, None)
+    uint4 = ScalarType.uint(4, None)
+    int8 = ScalarType.int_(8, None)
+    uint8 = ScalarType.uint(8, None)
+    float8_e4m3fn = ScalarType.float_(4, 3, True, NanRepr.EXTD_RANGE_MAX_MIN)
+    float8_e5m2 = ScalarType.float_IEEE754(5, 2)
+    float16_e8m7 = ScalarType.float_IEEE754(8, 7)
+    float16_e5m10 = ScalarType.float_IEEE754(5, 10)
+
+    # fp6, https://github.com/usyd-fsalab/fp6_llm/tree/main
+    float6_e3m2f = ScalarType.float_(3, 2, True, NanRepr.NONE)
+
+    # fp4, https://www.opencompute.org/documents/ocp-microscaling-formats-mx-v1-0-spec-final-pdf
+    float4_e2m1fn = ScalarType.float_(2, 1, True, NanRepr.NONE)
+
+    # "gptq" types
+    uint2b2 = ScalarType.uint(2, 2)
+    uint3b4 = ScalarType.uint(3, 4)
+    uint4b8 = ScalarType.uint(4, 8)
+    uint8b128 = ScalarType.uint(8, 128)
+
+    # colloquial names
+    bfloat16 = float16_e8m7
+    float16 = float16_e5m10