Fix: Respect sparsity_config.ignore in Cutlass Integration (#12517)

This PR addresses a bug in the Cutlass integration where the
`sparsity_config.ignore` list was not being respected. When only a
subset of modules were configured as Sparse24, the system incorrectly
selected Cutlass for non-sparse modules as well. This update ensures the
correct scheme is selected for non-sparse modules, fixing this behavior.

---

### Changes

- Updated logic to correctly respect `sparsity_config.ignore`.
- Ensured non-sparse modules use the appropriate scheme instead of
defaulting to Cutlass.

---

<details>
<summary>Testing Setup</summary>

The fix has been tested on top of [this
diff](https://github.com/vllm-project/vllm/pull/12097).

#### Steps to Test:
```bash
git checkout -b my-test-branch origin/rahul-bitmask-additions # compressed Cutlass support
git revert --no-edit aa2cd2c # revert Tyler's commit to turn off Cutlass for W16A16
git cherry-pick ca624cddb # this branch
```

#### Additional Patch Required:
```diff
diff --git a/vllm/model_executor/layers/quantization/compressed_tensors/compressed_tensors.py b/vllm/model_executor/layers/quantization/compressed_tensors/compressed_tensors.py
index a54177c1c..f916dd0c9 100644
--- a/vllm/model_executor/layers/quantization/compressed_tensors/compressed_tensors.py
+++ b/vllm/model_executor/layers/quantization/compressed_tensors/compressed_tensors.py
@@ -9,7 +9,7 @@ from compressed_tensors.quantization import (QuantizationArgs,
                                              QuantizationStrategy,
                                              QuantizationType)
 from pydantic import BaseModel
-
+from vllm.logger import init_logger
 from vllm.model_executor.layers.fused_moe import FusedMoE
 from vllm.model_executor.layers.linear import (LinearBase, LinearMethodBase,
                                                UnquantizedLinearMethod)
@@ -27,7 +27,7 @@ from vllm.model_executor.layers.quantization.compressed_tensors.utils import (
     should_ignore_layer)
 from vllm.model_executor.layers.quantization.kv_cache import BaseKVCacheMethod
 from vllm.platforms import current_platform
-
+logger = init_logger(__name__)
 __all__ = ["CompressedTensorsLinearMethod"]
 
 SPARSITY_CONFIG_NAME: Literal["sparsity_config"] = "sparsity_config"
```

Apply using:
```bash
git apply logging-patch.patch
```

</details>

---

<details>
<summary>Models Tested</summary>

- `nm-testing/TinyLlama-1.1B-Chat-v1.0-gsm8k-partial-24` 
- `nm-testing/TinyLlama-1.1B-Chat-v1.0-gsm8k-full-sparse24`
-
`nm-testing/TinyLlama-1.1B-Chat-v1.0-gsm8k-partial-24-entire-fp8-compressed`
-
`nm-testing/TinyLlama-1.1B-Chat-v1.0-gsm8k-partial-24-remaining-fp8-compressed`

</details>

---


<details>
<summary>Example Output</summary>

#### Layers 0-5 (Sparse24)
```
Using scheme: CompressedTensors24 for model.layers.0.self_attn.qkv_proj
Using scheme: CompressedTensors24 for model.layers.0.self_attn.o_proj
Using scheme: CompressedTensors24 for model.layers.0.mlp.gate_up_proj
Using scheme: CompressedTensors24 for model.layers.0.mlp.down_proj
...
```

#### Layers 6+ (Non-Sparse, FP8)
```
Using scheme: CompressedTensorsW8A8Fp8 for model.layers.6.self_attn.qkv_proj
Using scheme: CompressedTensorsW8A8Fp8 for model.layers.6.self_attn.o_proj
Using scheme: CompressedTensorsW8A8Fp8 for model.layers.6.mlp.gate_up_proj
Using scheme: CompressedTensorsW8A8Fp8 for model.layers.6.mlp.down_proj
...
```

</details>

**Note:** Assumed all modules in fused layers such as `QKV_proj` and
`Gate_up_proj` follow the same quantization/pruning scheme.

---

For related tasks using the Asana app for GitHub, refer to [[this
link](https://app.asana.com/0/0/1209227810815160)](https://app.asana.com/0/0/1209227810815160).

Signed-off-by: Rahul Tuli <rahul@neuralmagic.com>

vllm/model_executor/layers/quantization/compressed_tensors/compressed_tensors.py

@@ -1,4 +1,5 @@
-from typing import Any, Dict, List, Literal, Optional, cast
+from contextlib import suppress
+from typing import Any, Dict, List, Literal, Optional, Tuple, cast
 
 import torch
 from compressed_tensors.config import (CompressionFormat,
@@ -44,6 +45,7 @@ class CompressedTensorsConfig(QuantizationConfig):
         ignore: List[str],
         quant_format: str,
         sparsity_scheme_map: Dict[str, SparsityCompressionConfig],
+        sparsity_ignore_list: List[str],
         kv_cache_scheme: Optional[Dict[str, Any]] = None,
         config: Optional[Dict[str, Any]] = None,
     ):
@@ -54,6 +56,7 @@ class CompressedTensorsConfig(QuantizationConfig):
         self.target_scheme_map = target_scheme_map
         self.kv_cache_scheme = kv_cache_scheme
         self.sparsity_scheme_map = sparsity_scheme_map
+        self.sparsity_ignore_list = sparsity_ignore_list
         self.config = config
 
     def get_linear_method(self) -> "CompressedTensorsLinearMethod":
@@ -98,7 +101,7 @@ class CompressedTensorsConfig(QuantizationConfig):
         quant_format = cast(str, config.get("format"))
         target_scheme_map = cls._quantization_scheme_map_from_config(
             config=config)
-        sparsity_scheme_map = cls._sparsity_scheme_map_from_config(
+        sparsity_scheme_map, sparsity_ignore_list = cls._parse_sparsity_config(
             config=config)
 
         return cls(
@@ -106,20 +109,23 @@ class CompressedTensorsConfig(QuantizationConfig):
             ignore=ignore,
             quant_format=quant_format,
             sparsity_scheme_map=sparsity_scheme_map,
+            sparsity_ignore_list=sparsity_ignore_list,
             config=config,
         )
 
     @classmethod
-    def _sparsity_scheme_map_from_config(
+    def _parse_sparsity_config(
-            cls, config: Dict[str,
+        cls, config: Dict[str, Any]
-                              Any]) -> Dict[str, SparsityCompressionConfig]:
+    ) -> Tuple[Dict[str, SparsityCompressionConfig], List[str]]:
         """
         :param config: The `quantization_config` dictionary from config.json
-        :return: A dictionary mapping target layer names to their corresponding
+        :return: A tuple with two elements
-            sparsity compression configurations
+            1. A dictionary mapping target layer names to their corresponding
+                sparsity_config
+            2. A list of layer names to ignore for sparsity
         """
         if not (sparsity_config := config.get(SPARSITY_CONFIG_NAME)):
-            return dict()
+            return dict(), []
 
         sparsity_config = SparsityCompressionConfig.model_validate(
             sparsity_config)
@@ -127,7 +133,8 @@ class CompressedTensorsConfig(QuantizationConfig):
             target: sparsity_config
             for target in sparsity_config.targets or list()
         }
-        return sparse_scheme_map
+        sparsity_ignore_list = sparsity_config.ignore or list()
+        return sparse_scheme_map, sparsity_ignore_list
 
     @classmethod
     def _quantization_scheme_map_from_config(
@@ -352,7 +359,6 @@ class CompressedTensorsConfig(QuantizationConfig):
         """
         compressed-tensors supports non uniform in the following way:
 
-        ignore: List of layer_names or nn.Module names to be ignored.
         targets of config_groups: There can be N config_groups which each
             have a quantization scheme. Each config_group has a list of targets
             which can be a full layer_name, a regex for a layer_name, or
@@ -370,6 +376,8 @@ class CompressedTensorsConfig(QuantizationConfig):
         # need to make accelerate optional in ct to do this
 
         # Will be empty for models with only sparsity
+        weight_quant = input_quant = None
+        sparsity_scheme: Optional[SparsityCompressionConfig] = None
         if self.target_scheme_map:
             matched_target = find_matched_target(
                 layer_name=layer_name,
@@ -379,19 +387,24 @@ class CompressedTensorsConfig(QuantizationConfig):
             scheme_dict = self.target_scheme_map[matched_target]
             weight_quant = scheme_dict.get("weights")
             input_quant = scheme_dict.get("input_activations")
-        elif self.sparsity_scheme_map:
+
+        if self.sparsity_scheme_map:
+            is_ignored = False
+            with suppress(ValueError):
+                is_ignored = find_matched_target(
+                    layer_name=layer_name,
+                    module=layer,
+                    targets=self.sparsity_ignore_list)
+
+            # if the layer is in the sparsity ignore list,
+            # we should not apply any sparsity scheme
+
+            if not is_ignored:
                 matched_target = find_matched_target(
                     layer_name=layer_name,
                     module=layer,
                     targets=self.sparsity_scheme_map.keys())
-            weight_quant = None
+                sparsity_scheme = self.sparsity_scheme_map.get(matched_target)
-            input_quant = None
-
-        # For models with sparsity, assumes that the sparse layers are also
-        # quantized for cutlass 2:4 support
-        sparsity_scheme: Optional[
-            SparsityCompressionConfig] = self.sparsity_scheme_map.get(
-                matched_target)
 
         if self.supports_cutlass_24(weight_quant=weight_quant,
                                     input_quant=input_quant,
@@ -419,6 +432,8 @@ class CompressedTensorsConfig(QuantizationConfig):
         # Raise error if device does not support the scheme
         # (e.g. fp8 needs ada lovelace)
         self._check_scheme_supported(scheme.get_min_capability())
+        logger.debug("Using scheme: %s for %s", scheme.__class__.__name__,
+                     layer_name)
         return scheme
 
     def get_cache_scale(self, name: str) -> Optional[str]:

vllm/model_executor/layers/quantization/compressed_tensors/utils.py

@@ -12,7 +12,7 @@ def is_activation_quantization_format(format: str) -> bool:
     _ACTIVATION_QUANTIZATION_FORMATS = [
         CompressionFormat.naive_quantized.value,
         CompressionFormat.int_quantized.value,
-        CompressionFormat.float_quantized.value
+        CompressionFormat.float_quantized.value,
     ]
     return format in _ACTIVATION_QUANTIZATION_FORMATS
 
@@ -77,6 +77,53 @@ def check_equal_or_regex_match(layer_name: str,
     return False
 
 
+def _handle_fused_layers(func):
+    """
+    Decorator to handle fused layers by mapping vllm fused layer names
+    to their corresponding unfused layer names for quantization/pruning schemes.
+    """
+    # fused_layer_name -> unfused_layer_name
+    fused_layer_map = {
+        "qkv_proj": "q_proj",
+        "gate_up_proj": "up_proj",
+    }
+
+    def fused_layer_handler(layer_name: Optional[str], module: Module,
+                            targets: Iterable[str]) -> Optional[str]:
+        """
+        Wrapper function specifically designed to support the
+        find_matched_target function.
+
+        It handles cases where the provided layer name corresponds to a
+        fused layer in vllm, mapping it to its equivalent unfused layer name
+        based on the predefined fused_layer_map. If the original layer name
+        raises a ValueError in the wrapped function, this handler
+        will attempt to resolve the issue by substituting with unfused
+        layer name.
+
+        :param layer_name: Name of the layer, which may be fused.
+        :param module: An instance of torch.nn.Module.
+        :param targets: A list of target names or patterns to match.
+        :return: The result of the wrapped find_matched_target function with
+            the resolved layer name.
+        :raises ValueError: If the layer name cannot be resolved to a 
+            valid target.
+        """
+        try:
+            return func(layer_name, module, targets)
+        except ValueError:
+            if layer_name is None:
+                layer_name = ""
+            parent_name, fused_proj_name = layer_name.rsplit(".", 1)
+            unfused_proj_name = fused_layer_map.get(fused_proj_name,
+                                                    fused_proj_name)
+            new_layer_name = f"{parent_name}.{unfused_proj_name}"
+            return func(new_layer_name, module, targets)
+
+    return fused_layer_handler
+
+
+@_handle_fused_layers
 def find_matched_target(layer_name: Optional[str], module: Module,
                         targets: Iterable[str]) -> str:
     """
@@ -107,7 +154,8 @@ def find_matched_target(layer_name: Optional[str], module: Module,
                       or _match_fused_layer(layer_name, targets))
 
     if matched_target is None:
-        raise ValueError(f"Unable to find matching target for {module} in the "
+        raise ValueError(
+            f"Unable to find matching target for {layer_name} in the "
             "compressed-tensors config.")
 
     return matched_target