[Transform] Spinquant R3 (#1778)

## Purpose ##
* Support R3 for spinquant (without attention quantization, but possibly
with kv_cache quantization)

## Prerequisites ##
* #1651
* #1918
* vllm-project/compressed-tensors#485

## Changes ##
* Break out head dim inference
* Add attention target for spinquant mappings

## Testing ##
* Tested model coherence with llama 8b model

---------

Signed-off-by: Kyle Sayers <kylesayrs@gmail.com>

Author: kylesayrs

src/llmcompressor/modifiers/transform/spinquant/base.py

@@ -9,7 +9,7 @@
     TransformScheme,
     apply_transform_config,
 )
-from compressed_tensors.utils import TorchDtype
+from compressed_tensors.utils import TorchDtype, get_head_dim
 from pydantic import Field, ValidationInfo, field_validator
 from transformers import PreTrainedModel
 
@@ -129,16 +129,17 @@ def on_initialize(self, state: State, **kwargs) -> bool:
 
         self.mappings = infer_mapping_from_model(state.model)
         self.norm_mappings = infer_norm_mapping_from_model(state.model)
+        head_dim = get_head_dim(state.model.config)
 
         config_groups = {}
         if SpinquantRotation.R1 in self.rotations:
             config_groups["R1"] = self._create_r1_scheme()
 
         if SpinquantRotation.R2 in self.rotations:
-            config_groups["R2"] = self._create_r2_scheme(state.model)
+            config_groups["R2"] = self._create_r2_scheme(head_dim)
 
         if SpinquantRotation.R3 in self.rotations:
-            config_groups["R3"] = self._create_r3_scheme()
+            config_groups["R3"] = self._create_r3_scheme(head_dim)
 
         if SpinquantRotation.R4 in self.rotations:
             config_groups["R4"] = self._create_r4_scheme()
@@ -223,24 +224,7 @@ def _create_r1_scheme(self) -> TransformScheme:
             ],
         )
 
-    def _create_r2_scheme(self, model: PreTrainedModel) -> TransformScheme:
-        config = model.config
-
-        if hasattr(config, "head_dim"):
-            head_dim = config.head_dim
-        elif hasattr(config, "hidden_size") and hasattr(config, "num_attention_heads"):
-            head_dim = config.hidden_size // config.num_attention_heads
-        else:
-            raise NotImplementedError()
-
-        if self.transform_block_size:
-            if head_dim % self.transform_block_size != 0:
-                raise ValueError(
-                    f"transform_block_size {self.transform_block_size} must be set "
-                    f"such that model's head_dim {head_dim} is evenly divisible by it"
-                )
-            head_dim = self.transform_block_size
-
+    def _create_r2_scheme(self, head_dim: int) -> TransformScheme:
         return TransformScheme(
             type=self.transform_type,
             randomize=self.randomize,
@@ -257,9 +241,23 @@ def _create_r2_scheme(self, model: PreTrainedModel) -> TransformScheme:
             ],
         )
 
-    def _create_r3_scheme(self) -> TransformScheme:
-        raise NotImplementedError(
-            "SpinQuant R3 rotations will be added in a future release"
+    def _create_r3_scheme(self, head_dim: int) -> TransformScheme:
+        return TransformScheme(
+            type=self.transform_type,
+            randomize=self.randomize,
+            requires_grad=self.learnable,
+            precision=self.precision,
+            head_dim=head_dim,
+            apply=[
+                TransformArgs(
+                    targets=[self.mappings.attn],
+                    location="q_attn",
+                ),
+                TransformArgs(
+                    targets=[self.mappings.attn],
+                    location="k_cache",
+                ),
+            ],
         )
 
     def _create_r4_scheme(self) -> TransformScheme:

src/llmcompressor/modifiers/transform/spinquant/mappings.py

@@ -14,6 +14,7 @@ class SpinQuantMapping(BaseModel):
     layers (https://arxiv.org/pdf/2405.16406 Fig. 1).
 
     :param embedding: name or regex of embedding layer
+    :param attn: name or regex of attention block in decoder layer
     :param attn_q: name or regex of q_proj layer in attention block
     :param attn_k: name or regex of k_proj layer in attention block
     :param attn_v: name or regex of v_proj layer in attention block
@@ -29,6 +30,7 @@ class SpinQuantMapping(BaseModel):
 
     embedding: str
 
+    attn: str
     attn_q: str
     attn_k: str
     attn_v: str
@@ -50,6 +52,7 @@ def cast_to_list(cls, value):
 
 _default_mappings = SpinQuantMapping(
     embedding="re:.*embed_tokens$",
+    attn="re:.*self_attn$",
     attn_q="re:.*q_proj$",
     attn_k="re:.*k_proj$",
     attn_v="re:.*v_proj$",