init

vllm/model_executor/layers/quantization/schema.py

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+"""
+This file contains the Pydantic schemas for various quantization-related
+parameters. When a relevant quantization technique is specified, these
+parameters are loaded in the form of a JSON alongside the model weights
+and augment the model with additional information needed for use of that
+technique. The format of this JSON should be specified by one or more
+schemas contained here.
+
+For example, when the KV cache is quantized to FP8-E4M3 (currently only
+possible on ROCm), the model can be optionally augmented with KV cache
+scaling factors.
+"""
+
+from typing import Dict, Optional
+
+from pydantic import BaseModel, ConfigDict, ValidationInfo, model_validator
+
+
+class KVCacheQuantSchema(BaseModel):
+    dtype: str
+    # Each key is a TP rank. Each value is a dictionary mapping a TP rank's
+    # layer indices to their per-tensor KV cache scaling factor.
+    # TODO: Consider pulling this and its validation methods out into its
+    # own schema class (tricky as its members are variable)
+    scaling_factor: Dict[int, Dict[int, float]]
+
+    @model_validator(mode="after")
+    def check_is_fp8(self) -> "KVCacheQuantSchema":
+        assert self.dtype == "float8_e4m3fn", (
+            "Loaded scaling factors intended for KV cache dtype = "
+            f"{self.dtype} rather than float8_e4m3fn!")
+        return self
+
+    @model_validator(mode="after")
+    def check_tp_ranks(self, info: ValidationInfo) -> "KVCacheQuantSchema":
+        context = info.context
+        if context:
+            tp_size = context["tp_size"]
+            num_hidden_layers = context["num_hidden_layers"]
+            assert len(self.scaling_factor) == tp_size, (
+                f"Loaded dictionary has TP size {len(self.scaling_factor)} "
+                f"but LLM engine is currently running with TP size {tp_size}.")
+            for tp_rank, layer_maps in self.scaling_factor.items():
+                assert len(layer_maps) == num_hidden_layers, (
+                    f"KV cache scales map for TP rank {tp_rank} is malformed. "
+                    f"Expected {num_hidden_layers} layers, got "
+                    f"{len(layer_maps)}.")
+            for i in range(tp_size):
+                assert i in self.scaling_factor, (
+                    f"KV cache scales map for TP rank {i} not found.")
+        return self
+
+    @model_validator(mode="after")
+    def check_current_rank(self, info: ValidationInfo) -> "KVCacheQuantSchema":
+        context = info.context
+        if context:
+            tp_rank = context["tp_rank"]
+            num_hidden_layers = context["num_hidden_layers"]
+            layer_scales_map = self.scaling_factor[tp_rank]
+            for i in range(num_hidden_layers):
+                assert i in layer_scales_map, (
+                    f"Could not find KV cache scales for layer {i} in "
+                    f"TP rank {tp_rank}.")
+        return self
+
+
+class QuantParamSchema(BaseModel):
+    # TODO: Generalize and extend with more fields
+    # (e.g. weights/activations params) once functionality is enabled
+    model_config = ConfigDict(protected_namespaces=())
+    model_type: Optional[str]
+    kv_cache: KVCacheQuantSchema
+
+    @model_validator(mode="after")
+    def check_model_type(self, info: ValidationInfo) -> "QuantParamSchema":
+        context = info.context
+        if context:
+            model_type = context.get("model_type", None)
+            if model_type is not None:
+                assert model_type == self.model_type, (
+                    f"Model type is {model_type} but loaded "
+                    f"scaling factors belonging to different "
+                    f"model type {self.model_type}!")
+        return self