Remove flash patching for HF (#1436)

llmfoundry/models/hf/hf_causal_lm.py

@@ -256,23 +256,6 @@ def build_inner_model(
             False,  # Necessary due to https://github.com/huggingface/transformers/issues/28056
         )
 
-        # This is not ideal, however Hugging Face's _autoset_attn_implementation function
-        # forces you to load the model in fp16/bf16 if you want to use flash attention. Rather than loading
-        # the model and then casting it back to fp32, we are monkeypatching their check.
-        # https://github.com/huggingface/transformers/issues/28052
-        def _autoset_attn_implementation_monkeypatch(
-            cls,  # type: ignore
-            config,  # type: ignore
-            *args,  # type: ignore
-            **kwargs,  # type: ignore
-        ):  # type: ignore
-            config._attn_implementation = requested_attention_implementation
-            return config
-
-        PreTrainedModel._autoset_attn_implementation = classmethod(
-            _autoset_attn_implementation_monkeypatch,
-        )
-
         set_config_overrides(config, config_overrides)
 
         # We need to have all non-zero local ranks be not-pretrained
@@ -293,13 +276,16 @@ def _autoset_attn_implementation_monkeypatch(
                             pretrained_model_name_or_path,
                             trust_remote_code=trust_remote_code,
                             use_auth_token=use_auth_token,
+                            attn_implementation=
+                            requested_attention_implementation,
                             config=config,
                         )
             else:
                 with init_empty_weights(include_buffers=False):
                     AutoModelForCausalLM.from_config(
                         config,
                         trust_remote_code=trust_remote_code,
+                        attn_implementation=requested_attention_implementation,
                     )
 
         dist.barrier()
@@ -312,12 +298,14 @@ def _autoset_attn_implementation_monkeypatch(
                     trust_remote_code=trust_remote_code,
                     use_auth_token=use_auth_token,
                     load_in_8bit=load_in_8bit,
+                    attn_implementation=requested_attention_implementation,
                     config=config,
                 )
             else:
                 model = AutoModelForCausalLM.from_config(
                     config,
                     trust_remote_code=trust_remote_code,
+                    attn_implementation=requested_attention_implementation,
                 )
         elif resolved_init_device == 'meta':
             if pretrained:
@@ -328,6 +316,7 @@ def _autoset_attn_implementation_monkeypatch(
                 model = AutoModelForCausalLM.from_config(
                     config,
                     trust_remote_code=trust_remote_code,
+                    attn_implementation=requested_attention_implementation,
                 )
         else:
             raise ValueError(

tests/models/hf/test_hf_config.py

@@ -7,9 +7,11 @@
 from unittest.mock import Mock, patch
 
 import pytest
+import torch
 from omegaconf import OmegaConf as om
 from transformers import PretrainedConfig
 
+from llmfoundry.models.hf.hf_fsdp import rgetattr
 from llmfoundry.models.mpt import MPTConfig, MPTForCausalLM
 from llmfoundry.utils import build_tokenizer
 from llmfoundry.utils.builders import build_composer_model
@@ -235,3 +237,45 @@ def test_nested_override():
     assert isinstance(model.config.ffn_config, PretrainedConfig)
     # Ensure the other values still exist and are not set back to their defaults
     assert model.config.ffn_config.moe_num_experts == 16
+
+
+@pytest.mark.gpu
+def test_use_flash():
+    model_cfg = {
+        'name': 'hf_causal_lm',
+        'pretrained_model_name_or_path': 'codellama/CodeLlama-7b-hf',
+        'config_overrides': {
+            'num_hidden_layers': 2,
+            'hidden_size': 32,
+            'intermediate_size': 64,
+            'torch_dtype': 'bfloat16',
+        },
+        'pretrained': False,
+        'init_device': 'cpu',
+        'use_flash_attention_2': True,
+    }
+
+    name = model_cfg.pop('name')
+    model = build_composer_model(
+        name=name,
+        cfg=model_cfg,
+        tokenizer=None,  # type: ignore
+    )
+
+    from transformers.models.llama.modeling_llama import (
+        LlamaFlashAttention2,
+    )
+    flash_attn_class = LlamaFlashAttention2
+    attention_layers_attr = 'model.model.layers'
+    attention_attr = 'self_attn'
+
+    # check that it actually used flash attention 2
+    assert model.model.config._attn_implementation == ('flash_attention_2')
+    attention_layer = rgetattr(
+        rgetattr(model, attention_layers_attr)[0],
+        attention_attr,
+    )
+    assert isinstance(attention_layer, flash_attn_class)
+
+    # Make sure that HF has not cast the parameters to bf16
+    assert next(model.parameters()).dtype == torch.float32