[Model][VLM] Decouple weight loading logic for `Paligemma` (#8269)

vllm/model_executor/models/paligemma.py

+import itertools
 from typing import (Iterable, List, Literal, Mapping, Optional, Tuple,
                     TypedDict, Union)
 
@@ -13,7 +14,7 @@ from vllm.model_executor.layers.logits_processor import LogitsProcessor
 from vllm.model_executor.layers.quantization import QuantizationConfig
 from vllm.model_executor.layers.sampler import Sampler, SamplerOutput
 from vllm.model_executor.model_loader.weight_utils import default_weight_loader
-from vllm.model_executor.models.gemma import GemmaModel
+from vllm.model_executor.models.gemma import GemmaForCausalLM
 from vllm.model_executor.sampling_metadata import SamplingMetadata
 from vllm.multimodal import MULTIMODAL_REGISTRY
 from vllm.multimodal.utils import cached_get_tokenizer
@@ -22,14 +23,10 @@ from vllm.sequence import IntermediateTensors
 from .interfaces import SupportsMultiModal
 from .siglip import (SiglipVisionModel, dummy_image_for_siglip,
                      dummy_seq_data_for_siglip, get_max_siglip_image_tokens)
-from .utils import merge_multimodal_embeddings
+from .utils import filter_weights, merge_multimodal_embeddings
 
 logger = init_logger(__name__)
 
-_KEYS_TO_MODIFY_MAPPING = {
-    "language_model.model": "language_model",
-}
-
 
 class PaliGemmaImagePixelInputs(TypedDict):
     type: Literal["pixel_values"]
@@ -151,8 +148,8 @@ class PaliGemmaForConditionalGeneration(nn.Module, SupportsMultiModal):
             projection_dim=config.vision_config.projection_dim)
 
         self.quant_config = quant_config
-        self.language_model = GemmaModel(config.text_config, cache_config,
-                                         quant_config)
+        self.language_model = GemmaForCausalLM(config.text_config,
+                                               cache_config, quant_config)
         self.unpadded_vocab_size = config.text_config.vocab_size
         logit_scale = getattr(config, "logit_scale", 1.0)
         self.logits_processor = LogitsProcessor(self.unpadded_vocab_size,
@@ -252,7 +249,8 @@ class PaliGemmaForConditionalGeneration(nn.Module, SupportsMultiModal):
             vision_embeddings = vision_embeddings * (self.config.hidden_size**
                                                      -0.5)
 
-            inputs_embeds = self.language_model.get_input_embeddings(input_ids)
+            inputs_embeds = self.language_model.model.get_input_embeddings(
+                input_ids)
 
             inputs_embeds = merge_multimodal_embeddings(
                 input_ids, inputs_embeds, vision_embeddings,
@@ -262,7 +260,7 @@ class PaliGemmaForConditionalGeneration(nn.Module, SupportsMultiModal):
         else:
             inputs_embeds = None
 
-        hidden_states = self.language_model(input_ids,
+        hidden_states = self.language_model.model(input_ids,
                                                   positions,
                                                   kv_caches,
                                                   attn_metadata,
@@ -271,78 +269,38 @@ class PaliGemmaForConditionalGeneration(nn.Module, SupportsMultiModal):
 
         return hidden_states
 
-    # Copied from vllm/model_executor/models/gemma.py
     def compute_logits(
         self,
         hidden_states: torch.Tensor,
         sampling_metadata: SamplingMetadata,
     ) -> Optional[torch.Tensor]:
-        logits = self.logits_processor(self.language_model.embed_tokens,
-                                       hidden_states, sampling_metadata)
-        return logits
+        return self.language_model.compute_logits(hidden_states,
+                                                  sampling_metadata)
 
-    # Copied from vllm/model_executor/models/gemma.py
     def sample(
         self,
         logits: torch.Tensor,
         sampling_metadata: SamplingMetadata,
     ) -> Optional[SamplerOutput]:
-        next_tokens = self.sampler(logits, sampling_metadata)
-        return next_tokens
+        return self.language_model.sample(logits, sampling_metadata)
 
-    # Adapted from vllm/model_executor/models/gemma.py
     def load_weights(self, weights: Iterable[Tuple[str, torch.Tensor]]):
-        stacked_params_mapping = [
-            # (param_name, shard_name, shard_id)
-            ("qkv_proj", "q_proj", "q"),
-            ("qkv_proj", "k_proj", "k"),
-            ("qkv_proj", "v_proj", "v"),
-            ("gate_up_proj", "gate_proj", 0),
-            ("gate_up_proj", "up_proj", 1),
-        ]
-        params_dict = dict(self.named_parameters())
-        loaded_params = set()
-        for name, loaded_weight in weights:
-            for key_to_modify, new_key in _KEYS_TO_MODIFY_MAPPING.items():
-                if key_to_modify in name:
-                    name = name.replace(key_to_modify, new_key)
-            use_default_weight_loading = False
-            if "vision" not in name or self.vision_tower.shard_weight:
-                for (param_name, shard_name,
-                     shard_id) in stacked_params_mapping:
-                    if shard_name not in name:
-                        continue
-                    name = name.replace(shard_name, param_name)
-                    # Skip loading extra bias for GPTQ models.
-                    if name.endswith(".bias") and name not in params_dict:
-                        continue
-                    param = params_dict[name]
-                    weight_loader = param.weight_loader
-                    weight_loader(param, loaded_weight, shard_id)
-                    break
-                else:
-                    # lm_head is not used in vllm as it is tied with
-                    # embed_token. To prevent errors, skip loading
-                    # lm_head.weight.
-                    if "lm_head.weight" in name:
-                        continue
-                    # Skip loading extra bias for GPTQ models.
-                    if name.endswith(".bias") and name not in params_dict:
-                        continue
-                    use_default_weight_loading = True
-            else:
-                use_default_weight_loading = True
-
-            if use_default_weight_loading:
-                param = params_dict[name]
+        # prepare weight iterators for components
+        vit_weights, mlp_weights, llm_weights = itertools.tee(weights, 3)
+
+        # load vision tower
+        vit_weights = filter_weights(vit_weights, "vision_tower")
+        self.vision_tower.load_weights(vit_weights)
+
+        # load mlp projector
+        mlp_weights = filter_weights(mlp_weights, "multi_modal_projector")
+        mlp_params_dict = dict(self.multi_modal_projector.named_parameters())
+        for name, loaded_weight in mlp_weights:
+            param = mlp_params_dict[name]
             weight_loader = getattr(param, "weight_loader",
                                     default_weight_loader)
             weight_loader(param, loaded_weight)
 
-            loaded_params.add(name)
-
-        unloaded_params = params_dict.keys() - loaded_params
-        if unloaded_params:
-            logger.warning(
-                "Some weights are not initialized from checkpoints: %s",
-                unloaded_params)
+        # load llm backbone
+        llm_weights = filter_weights(llm_weights, "language_model")
+        self.language_model.load_weights(llm_weights)

vllm/model_executor/models/siglip.py

@@ -529,6 +529,12 @@ class SiglipVisionModel(nn.Module):
         )
 
     def load_weights(self, weights: Iterable[Tuple[str, torch.Tensor]]):
+        stacked_params_mapping = [
+            # (param_name, shard_name, shard_id)
+            ("qkv_proj", "q_proj", "q"),
+            ("qkv_proj", "k_proj", "k"),
+            ("qkv_proj", "v_proj", "v"),
+        ] if self.shard_weight else []
         params_dict = dict(self.named_parameters())
         layer_count = len(self.vision_model.encoder.layers)
 
@@ -544,6 +550,15 @@ class SiglipVisionModel(nn.Module):
                 if layer_idx >= layer_count:
                     continue
 
+            for (param_name, weight_name, shard_id) in stacked_params_mapping:
+                if weight_name not in name:
+                    continue
+
+                param = params_dict[name.replace(weight_name, param_name)]
+                weight_loader = param.weight_loader
+                weight_loader(param, loaded_weight, shard_id)
+                break
+            else:
                 param = params_dict[name]
                 weight_loader = getattr(param, "weight_loader",
                                         default_weight_loader)