Add sdpa support for Albert (#32092)

* Add sdpa support for Albert * [run_slow] albert * Add benchmarks and PR suggestion * Fix quality * Fix * [run_slow] albert
huggingface · Sep 3, 2024 · 03c12d0 · 03c12d0
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diff --git a/docs/source/en/model_doc/albert.md b/docs/source/en/model_doc/albert.md
@@ -59,7 +59,52 @@ This model was contributed by [lysandre](https://huggingface.co/lysandre). This
 - Layers are split in groups that share parameters (to save memory).
 Next sentence prediction is replaced by a sentence ordering prediction: in the inputs, we have two sentences A and B (that are consecutive) and we either feed A followed by B or B followed by A. The model must predict if they have been swapped or not.
 
-
+### Using Scaled Dot Product Attention (SDPA)
+
+PyTorch includes a native scaled dot-product attention (SDPA) operator as part of `torch.nn.functional`. This function 
+encompasses several implementations that can be applied depending on the inputs and the hardware in use. See the 
+[official documentation](https://pytorch.org/docs/stable/generated/torch.nn.functional.scaled_dot_product_attention.html) 
+or the [GPU Inference](https://huggingface.co/docs/transformers/main/en/perf_infer_gpu_one#pytorch-scaled-dot-product-attention)
+page for more information.
+
+SDPA is used by default for `torch>=2.1.1` when an implementation is available, but you may also set 
+`attn_implementation="sdpa"` in `from_pretrained()` to explicitly request SDPA to be used.
+
+```
+from transformers import AlbertModel
+model = AlbertModel.from_pretrained("albert/albert-base-v1", torch_dtype=torch.float16, attn_implementation="sdpa")
+...
+```
+
+For the best speedups, we recommend loading the model in half-precision (e.g. `torch.float16` or `torch.bfloat16`).
+
+On a local benchmark (GeForce RTX 2060-8GB, PyTorch 2.3.1, OS Ubuntu 20.04) with `float16`, we saw the 
+following speedups during training and inference.
+
+#### Training for 100 iterations
+
+|batch_size|seq_len|Time per batch (eager - s)| Time per batch (sdpa - s)| Speedup (%)| Eager peak mem (MB)| sdpa peak mem (MB)| Mem saving (%)|
+|----------|-------|--------------------------|--------------------------|------------|--------------------|-------------------|---------------|
+|2         |256    |0.028                     |0.024                     |14.388      |358.411             |321.088            |11.624         |
+|2         |512    |0.049                     |0.041                     |17.681      |753.458             |602.660            |25.022         |
+|4         |256    |0.044                     |0.039                     |12.246      |679.534             |602.660            |12.756         |
+|4         |512    |0.090                     |0.076                     |18.472      |1434.820            |1134.140           |26.512         |
+|8         |256    |0.081                     |0.072                     |12.664      |1283.825            |1134.140           |13.198         |
+|8         |512    |0.170                     |0.143                     |18.957      |2820.398            |2219.695           |27.062         |
+
+#### Inference with 50 batches
+
+|batch_size|seq_len|Per token latency eager (ms)|Per token latency SDPA (ms)|Speedup (%) |Mem eager (MB)|Mem BT (MB)|Mem saved (%)|
+|----------|-------|----------------------------|---------------------------|------------|--------------|-----------|-------------|
+|4         |128    |0.083                       |0.071                      |16.967      |48.319        |48.45      |-0.268       |
+|4         |256    |0.148                       |0.127                      |16.37       |63.4          |63.922     |-0.817       |
+|4         |512    |0.31                        |0.247                      |25.473      |110.092       |94.343     |16.693       |
+|8         |128    |0.137                       |0.124                      |11.102      |63.4          |63.66      |-0.409       |
+|8         |256    |0.271                       |0.231                      |17.271      |91.202        |92.246     |-1.132       |
+|8         |512    |0.602                       |0.48                       |25.47       |186.159       |152.564    |22.021       |
+|16        |128    |0.252                       |0.224                      |12.506      |91.202        |91.722     |-0.567       |
+|16        |256    |0.526                       |0.448                      |17.604      |148.378       |150.467    |-1.388       |
+|16        |512    |1.203                       |0.96                       |25.365      |338.293       |271.102    |24.784       |
 
 This model was contributed by [lysandre](https://huggingface.co/lysandre). This model jax version was contributed by
 [kamalkraj](https://huggingface.co/kamalkraj). The original code can be found [here](https://github.com/google-research/ALBERT).

diff --git a/docs/source/en/perf_infer_gpu_one.md b/docs/source/en/perf_infer_gpu_one.md
@@ -201,6 +201,7 @@ FlashAttention is more memory efficient, meaning you can train on much larger se
 PyTorch's [`torch.nn.functional.scaled_dot_product_attention`](https://pytorch.org/docs/master/generated/torch.nn.functional.scaled_dot_product_attention.html) (SDPA) can also call FlashAttention and memory-efficient attention kernels under the hood. SDPA support is currently being added natively in Transformers and is used by default for `torch>=2.1.1` when an implementation is available. You may also set `attn_implementation="sdpa"` in `from_pretrained()` to explicitly request SDPA to be used.
 
 For now, Transformers supports SDPA inference and training for the following architectures:
+* [Albert](https://huggingface.co/docs/transformers/model_doc/albert#transformers.AlbertModel)
 * [Audio Spectrogram Transformer](https://huggingface.co/docs/transformers/model_doc/audio-spectrogram-transformer#transformers.ASTModel)
 * [Bart](https://huggingface.co/docs/transformers/model_doc/bart#transformers.BartModel)
 * [Bert](https://huggingface.co/docs/transformers/model_doc/bert#transformers.BertModel)

diff --git a/src/transformers/models/albert/modeling_albert.py b/src/transformers/models/albert/modeling_albert.py
@@ -24,6 +24,7 @@
 from torch.nn import BCEWithLogitsLoss, CrossEntropyLoss, MSELoss
 
 from ...activations import ACT2FN
+from ...modeling_attn_mask_utils import _prepare_4d_attention_mask_for_sdpa
 from ...modeling_outputs import (
     BaseModelOutput,
     BaseModelOutputWithPooling,
@@ -34,7 +35,12 @@
     TokenClassifierOutput,
 )
 from ...modeling_utils import PreTrainedModel
-from ...pytorch_utils import apply_chunking_to_forward, find_pruneable_heads_and_indices, prune_linear_layer
+from ...pytorch_utils import (
+    apply_chunking_to_forward,
+    find_pruneable_heads_and_indices,
+    is_torch_greater_or_equal_than_2_2,
+    prune_linear_layer,
+)
 from ...utils import (
     ModelOutput,
     add_code_sample_docstrings,
@@ -358,6 +364,66 @@ def forward(
         return (layernormed_context_layer, attention_probs) if output_attentions else (layernormed_context_layer,)
 
 
+class AlbertSdpaAttention(AlbertAttention):
+    def __init__(self, config):
+        super().__init__(config)
+        self.dropout_prob = config.attention_probs_dropout_prob
+        self.require_contiguous_qkv = not is_torch_greater_or_equal_than_2_2
+
+    def forward(
+        self,
+        hidden_states: torch.Tensor,
+        attention_mask: Optional[torch.FloatTensor] = None,
+        head_mask: Optional[torch.FloatTensor] = None,
+        output_attentions: bool = False,
+    ) -> Union[Tuple[torch.Tensor], Tuple[torch.Tensor, torch.Tensor]]:
+        if self.position_embedding_type != "absolute" or output_attentions or head_mask is not None:
+            logger.warning(
+                "AlbertSdpaAttention is used but `torch.nn.functional.scaled_dot_product_attention` does not support "
+                "non-absolute `position_embedding_type` or `output_attentions=True` or `head_mask`. Falling back to "
+                "the eager attention implementation, but specifying the eager implementation will be required from "
+                "Transformers version v5.0.0 onwards. This warning can be removed using the argument "
+                '`attn_implementation="eager"` when loading the model.'
+            )
+            return super().forward(hidden_states, attention_mask, head_mask, output_attentions)
+
+        batch_size, seq_len, _ = hidden_states.size()
+        query_layer = self.transpose_for_scores(self.query(hidden_states))
+        key_layer = self.transpose_for_scores(self.key(hidden_states))
+        value_layer = self.transpose_for_scores(self.value(hidden_states))
+
+        # SDPA with memory-efficient backend is broken in torch==2.1.2 when using non-contiguous inputs and a custom
+        # attn_mask, so we need to call `.contiguous()` here. This was fixed in torch==2.2.0.
+        # Reference: https://github.com/pytorch/pytorch/issues/112577
+        if self.require_contiguous_qkv and query_layer.device.type == "cuda" and attention_mask is not None:
+            query_layer = query_layer.contiguous()
+            key_layer = key_layer.contiguous()
+            value_layer = value_layer.contiguous()
+
+        attention_output = torch.nn.functional.scaled_dot_product_attention(
+            query=query_layer,
+            key=key_layer,
+            value=value_layer,
+            attn_mask=attention_mask,
+            dropout_p=self.dropout_prob if self.training else 0.0,
+            is_causal=False,
+        )
+
+        attention_output = attention_output.transpose(1, 2)
+        attention_output = attention_output.reshape(batch_size, seq_len, self.all_head_size)
+
+        projected_context_layer = self.dense(attention_output)
+        projected_context_layer_dropout = self.output_dropout(projected_context_layer)
+        layernormed_context_layer = self.LayerNorm(hidden_states + projected_context_layer_dropout)
+        return (layernormed_context_layer,)
+
+
+ALBERT_ATTENTION_CLASSES = {
+    "eager": AlbertAttention,
+    "sdpa": AlbertSdpaAttention,
+}
+
+
 class AlbertLayer(nn.Module):
     def __init__(self, config: AlbertConfig):
         super().__init__()
@@ -366,7 +432,7 @@ def __init__(self, config: AlbertConfig):
         self.chunk_size_feed_forward = config.chunk_size_feed_forward
         self.seq_len_dim = 1
         self.full_layer_layer_norm = nn.LayerNorm(config.hidden_size, eps=config.layer_norm_eps)
-        self.attention = AlbertAttention(config)
+        self.attention = ALBERT_ATTENTION_CLASSES[config._attn_implementation](config)
         self.ffn = nn.Linear(config.hidden_size, config.intermediate_size)
         self.ffn_output = nn.Linear(config.intermediate_size, config.hidden_size)
         self.activation = ACT2FN[config.hidden_act]
@@ -496,6 +562,7 @@ class AlbertPreTrainedModel(PreTrainedModel):
     config_class = AlbertConfig
     load_tf_weights = load_tf_weights_in_albert
     base_model_prefix = "albert"
+    _supports_sdpa = True
 
     def _init_weights(self, module):
         """Initialize the weights."""
@@ -635,6 +702,9 @@ def __init__(self, config: AlbertConfig, add_pooling_layer: bool = True):
             self.pooler = None
             self.pooler_activation = None
 
+        self.attn_implementation = config._attn_implementation
+        self.position_embedding_type = config.position_embedding_type
+
         # Initialize weights and apply final processing
         self.post_init()
 
@@ -708,14 +778,28 @@ def forward(
             else:
                 token_type_ids = torch.zeros(input_shape, dtype=torch.long, device=device)
 
-        extended_attention_mask = attention_mask.unsqueeze(1).unsqueeze(2)
-        extended_attention_mask = extended_attention_mask.to(dtype=self.dtype)  # fp16 compatibility
-        extended_attention_mask = (1.0 - extended_attention_mask) * torch.finfo(self.dtype).min
-        head_mask = self.get_head_mask(head_mask, self.config.num_hidden_layers)
-
         embedding_output = self.embeddings(
             input_ids, position_ids=position_ids, token_type_ids=token_type_ids, inputs_embeds=inputs_embeds
         )
+
+        use_sdpa_attention_mask = (
+            self.attn_implementation == "sdpa"
+            and self.position_embedding_type == "absolute"
+            and head_mask is None
+            and not output_attentions
+        )
+
+        if use_sdpa_attention_mask:
+            extended_attention_mask = _prepare_4d_attention_mask_for_sdpa(
+                attention_mask, embedding_output.dtype, tgt_len=seq_length
+            )
+        else:
+            extended_attention_mask = attention_mask.unsqueeze(1).unsqueeze(2)
+            extended_attention_mask = extended_attention_mask.to(dtype=self.dtype)  # fp16 compatibility
+            extended_attention_mask = (1.0 - extended_attention_mask) * torch.finfo(self.dtype).min
+
+        head_mask = self.get_head_mask(head_mask, self.config.num_hidden_layers)
+
         encoder_outputs = self.encoder(
             embedding_output,
             extended_attention_mask,