Llama flash attention module. This module inherits from `LlamaAttention` as the weights of the module stays
untouched. The only required change would be on the forward pass where it needs to correctly call the public API of
flash attention and deal with padding tokens in case the input contains any of them.
"""
def__init__(self,*args,**kwargs):
super().__init__(*args,**kwargs)
# TODO: Should be removed once Flash Attention for RoCm is bumped to 2.1.
# flash_attn<2.1 generates top-left aligned causal mask, while what is needed here is bottom-right alignement, that was made default for flash_attn>=2.1. This attribute is used to handle this difference. Reference: https://github.com/Dao-AILab/flash-attention/releases/tag/v2.1.0.
# Beware that with flash_attn<2.1, using q_seqlen != k_seqlen (except for the case q_seqlen == 1) produces a wrong mask (top-left).
# TODO: These transpose are quite inefficient but Flash Attention requires the layout [batch_size, sequence_length, num_heads, head_dim]. We would need to refactor the KV cache
# to be able to avoid many of these transpose/reshape/view.
# TODO: Improve this warning with e.g. `model.config.attn_implementation = "manual"` once this is implemented.
logger.warning_once(
"LlamaModel is using LlamaSdpaAttention, but `torch.nn.functional.scaled_dot_product_attention` does not support `output_attentions=True`. Falling back to the manual attention implementation, "
'but specifying the manual 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.'
)
returnsuper().forward(
hidden_states=hidden_states,
attention_mask=attention_mask,
position_ids=position_ids,
past_key_value=past_key_value,
output_attentions=output_attentions,
use_cache=use_cache,
cache_position=cache_position,
position_embeddings=position_embeddings,
)
bsz,q_len,_=hidden_states.size()
query_states=self.q_proj(hidden_states)
key_states=self.k_proj(hidden_states)
value_states=self.v_proj(hidden_states)
query_states=query_states.view(
bsz,q_len,self.num_heads,self.head_dim
).transpose(1,2)
key_states=key_states.view(
bsz,q_len,self.num_key_value_heads,self.head_dim
).transpose(1,2)
value_states=value_states.view(
bsz,q_len,self.num_key_value_heads,self.head_dim
).transpose(1,2)
ifposition_embeddingsisNone:
logger.warning_once(
"The attention layers in this model are transitioning from computing the RoPE embeddings internally "
"through `position_ids` (2D tensor with the indexes of the tokens), to using externally computed "
"`position_embeddings` (Tuple of tensors, containing cos and sin). In v4.45 `position_ids` will be "
"removed and `position_embeddings` will be mandatory."