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"""Flash attention monkey patch for mistral model"""
# pylint: disable=duplicate-code
import logging
from typing import List, Optional, Tuple, Union
import torch
import transformers
from einops import rearrange
from flash_attn.bert_padding import pad_input, unpad_input
from flash_attn.flash_attn_interface import ( # pylint: disable=ungrouped-imports
flash_attn_kvpacked_func,
flash_attn_varlen_kvpacked_func,
flash_attn_varlen_qkvpacked_func,
)
from transformers.modeling_outputs import BaseModelOutputWithPast
from transformers.models.mistral.modeling_mistral import (
MistralAttention as OriginalMistralAttention,
)
from transformers.models.mistral.modeling_mistral import (
MistralDecoderLayer as OriginalMistralDecoderLayer,
)
from transformers.models.mistral.modeling_mistral import apply_rotary_pos_emb, repeat_kv
from axolotl.monkeypatch.utils import get_cu_seqlens_from_pos_ids
LOG = logging.getLogger("axolotl.monkeypatch.mistral")
def replace_mistral_attn_with_flash_attn(
packed: Optional[bool] = False,
):
transformers.models.mistral.modeling_mistral.MistralModel._prepare_decoder_attention_mask = ( # pylint: disable=protected-access
_prepare_decoder_attention_mask
)
transformers.models.mistral.modeling_mistral.MistralAttention.forward = (
flashattn_forward
)
if packed:
transformers.models.mistral.modeling_mistral.MistralDecoderLayer = (
MistralDecoderLayer
)
transformers.models.mistral.modeling_mistral.MistralModel.forward = (
mistral_model_forward
)
@torch.jit.script
def _make_sliding_window_causal_mask(
bsz: int,
tgt_len: int,
dtype: torch.dtype,
device: torch.device,
past_key_values_length: int = 0,
sliding_window: int = 4096,
):
"""
Make causal mask used for sliding window attention
"""
tensor = torch.full(
(tgt_len, tgt_len),
fill_value=1,
device=device,
)
mask = torch.tril(tensor, diagonal=0)
# make the mask banded to account for sliding window
# NOTE: HF implementation is wrong as of 14-10-2023 for torch.triu, needs +1
mask = torch.triu(mask, diagonal=-sliding_window + 1)
mask = torch.log(mask).to(dtype)
if past_key_values_length > 0:
mask = torch.cat(
[
torch.zeros(
tgt_len, past_key_values_length, dtype=dtype, device=device
),
mask,
],
dim=-1,
)
return mask[None, None, :, :].expand(
bsz, 1, tgt_len, tgt_len + past_key_values_length
)
# Disable the transformation of the attention mask in LlamaModel as the flash attention
# requires the attention mask to be the same as the key_padding_mask
def _prepare_decoder_attention_mask(
self,
attention_mask,
input_shape,
inputs_embeds,
past_key_values_length,
sliding_window,
): # pylint: disable=unused-argument
# [bsz, seq_len]
if attention_mask is None:
return attention_mask
# NOTE: attention mask and sliding masks are only broadcastable in certain scenarios.
# Without attention_mask.shape[0] == 1, error will trigger after eval loss but only when wandb is enabled.
if input_shape[-1] > 1 and attention_mask.shape[0] == 1:
sliding_window_mask = _make_sliding_window_causal_mask(
bsz=input_shape[0],
tgt_len=input_shape[1],
dtype=inputs_embeds.dtype,
device=inputs_embeds.device,
past_key_values_length=past_key_values_length,
sliding_window=sliding_window,
)
attention_mask = attention_mask + sliding_window_mask
else:
LOG.info("skipping sliding window mask, not broadcastable with attention mask")
return attention_mask
def flashattn_forward(
self: OriginalMistralAttention,
hidden_states: torch.Tensor,
attention_mask: Optional[torch.Tensor] = None,
position_ids: Optional[torch.LongTensor] = None,
past_key_value: Optional[Tuple[torch.Tensor]] = None,
output_attentions: bool = False,
use_cache: bool = False,
cu_seqlens: Optional[torch.Tensor] = None,
max_seqlen: Optional[torch.Tensor] = None,
) -> Tuple[torch.Tensor, Optional[torch.Tensor], Optional[Tuple[torch.Tensor]]]:
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)
kv_seq_len = key_states.shape[-2]
if past_key_value is not None:
kv_seq_len += past_key_value[0].shape[-2]
cos, sin = self.rotary_emb(value_states, seq_len=kv_seq_len)
query_states, key_states = apply_rotary_pos_emb(
query_states, key_states, cos, sin, position_ids
)
use_sliding_windows = (
hasattr(self.config, "sliding_window") is not None
and kv_seq_len > self.config.sliding_window
)
if use_sliding_windows:
window_size = (self.config.sliding_window, self.config.sliding_window)
else:
window_size = (-1, -1)
if past_key_value is not None:
# Activate slicing cache only if the config has a value `sliding_windows` attribute
if (
hasattr(self.config, "sliding_window")
and kv_seq_len > self.config.sliding_window
):
slicing_tokens = kv_seq_len - self.config.sliding_window
past_key = past_key_value[0]
past_value = past_key_value[1]
past_key = past_key[:, :, slicing_tokens:, :].contiguous()
past_value = past_value[:, :, slicing_tokens:, :].contiguous()
if past_key.shape[-2] != self.config.sliding_window - 1:
raise ValueError(
f"past key much have a shape of (`batch_size, num_heads, self.config.sliding_window-1, head_dim`), got"
f" {past_key.shape}"
)
past_key_value = (past_key, past_value) if use_cache else None
if past_key_value is not None:
key_states = torch.cat([past_key_value[0], key_states], dim=2)
value_states = torch.cat([past_key_value[1], value_states], dim=2)
past_key_value = (key_states, value_states) if use_cache else None
# repeat k/v heads if n_kv_heads < n_heads
key_states = repeat_kv(key_states, self.num_key_value_groups)
value_states = repeat_kv(value_states, self.num_key_value_groups)
if self.training:
# during training q,k,v always have same seqlen
assert key_states.shape == query_states.shape
is_causal = True
else:
# turn off FA causal mask after first inference autoregressive iteration
# only on first autoregressive step q,k,v have same seqlen
is_causal = key_states.shape == query_states.shape
dropout_rate = 0.0 if not self.training else getattr(self, "attention_dropout", 0.0)
if cu_seqlens is not None and max_seqlen is not None and cu_seqlens.dim() == 1:
# special handling using sample packing
qkv = torch.stack(
[query_states, key_states, value_states], dim=2
) # [bsz, nh, 3, q_len, hd]
qkv = qkv.transpose(1, 3) # [bsz, q_len, 3, nh, hd]
qkv = rearrange(qkv, "b s ... -> (b s) ...")
output = flash_attn_varlen_qkvpacked_func(
qkv,
cu_seqlens,
max_seqlen,
dropout_p=dropout_rate,
softmax_scale=None,
causal=True,
window_size=window_size,
)
output = rearrange(output, "(b s) ... -> b s ...", b=bsz)
elif query_states.shape == key_states.shape:
query_states = query_states.transpose(1, 2)
key_states = key_states.transpose(1, 2)
value_states = value_states.transpose(1, 2)
qkv_unpad, cu_seqlens_q, max_seqlen_q, _, output_pad_fn = generate_qkv(
query_states,
key_states,
value_states,
qkvpacked=True,
# We have disabled _prepare_decoder_attention_mask in LlamaModel
# the attention_mask should be the same as the key_padding_mask
key_padding_mask=attention_mask,
query_padding_mask=attention_mask[:, -query_states.size(1) :]
if attention_mask is not None
else None,
)
output_unpad = flash_attn_varlen_qkvpacked_func(
qkv_unpad,
cu_seqlens_q,
max_seqlen_q,
dropout_p=dropout_rate,
softmax_scale=None,
causal=is_causal,
window_size=window_size,
)
output = output_pad_fn(output_unpad)
else:
query_states = query_states.transpose(1, 2)
key_states = key_states.transpose(1, 2)
value_states = value_states.transpose(1, 2)
if attention_mask is None or attention_mask.all().item():
output = flash_attn_kvpacked_func(
query_states,
torch.stack([key_states, value_states], 2),
dropout_p=dropout_rate,
causal=is_causal,
window_size=window_size,
)
else:
( # pylint: disable=unbalanced-tuple-unpacking
q_unpad,
kv_unpad,
cu_seqlens_q,
cu_seqlens_k,
max_seqlen_q,
max_seqlen_k,
_,
_,
output_pad_fn,
) = generate_qkv(
query_states,
key_states,
value_states,
kvpacked=True,
key_padding_mask=attention_mask,
query_padding_mask=attention_mask[:, -query_states.size(1) :]
if attention_mask is not None
else None,
)
if q_unpad.dtype != kv_unpad.dtype:
kv_unpad = kv_unpad.to(q_unpad.dtype)
output_unpad = flash_attn_varlen_kvpacked_func(
q_unpad,
kv_unpad,
cu_seqlens_q,
cu_seqlens_k,
max_seqlen_q,
max_seqlen_k,
dropout_p=dropout_rate,
softmax_scale=None,
causal=is_causal,
window_size=window_size,
)
output = output_pad_fn(output_unpad)
attn_output = output
if attn_output.size() != (bsz, q_len, self.num_heads, self.head_dim):
raise ValueError(
f"`attn_output` should be of size {(bsz, q_len, self.num_heads, self.head_dim)}, but is"
f" {attn_output.size()}"
)
attn_output = rearrange(attn_output, "b s h d -> b s (h d)")
attn_output = self.o_proj(attn_output)
if not output_attentions:
attn_weights = None
return attn_output, attn_weights, past_key_value
# based on https://github.com/Dao-AILab/flash-attention/blob/364a5b/tests/test_flash_attn.py#L38
def generate_qkv(
q,
k,
v,
query_padding_mask=None,
key_padding_mask=None,
kvpacked=False,
qkvpacked=False,
): # pylint: disable=invalid-name,unnecessary-lambda-assignment
"""
Arguments:
q: (batch_size, seqlen_q, nheads, d)
k: (batch_size, seqlen_k, nheads_k, d)
v: (batch_size, seqlen_k, nheads_k, d)
query_padding_mask: (batch_size, seqlen), bool
key_padding_mask: (batch_size, seqlen), bool
"""
assert not (kvpacked and qkvpacked)
batch_size, seqlen_q, nheads, d = q.shape
_, seqlen_k, nheads_k, _ = k.shape
assert k.shape == (batch_size, seqlen_k, nheads_k, d)
assert v.shape == (batch_size, seqlen_k, nheads_k, d)
if query_padding_mask is not None:
q_unpad, indices_q, cu_seqlens_q, max_seqlen_q = unpad_input(
q, query_padding_mask
)
output_pad_fn = lambda output_unpad: pad_input( # noqa: E731
output_unpad, indices_q, batch_size, seqlen_q
)
else:
q_unpad = rearrange(q, "b s h d -> (b s) h d")
cu_seqlens_q = torch.arange(
0,
(batch_size + 1) * seqlen_q,
step=seqlen_q,
dtype=torch.int32,
device=q_unpad.device,
)
max_seqlen_q = seqlen_q
output_pad_fn = lambda output_unpad: rearrange( # noqa: E731
output_unpad, "(b s) h d -> b s h d", b=batch_size
)
if key_padding_mask is not None:
k_unpad, _, cu_seqlens_k, max_seqlen_k = unpad_input(k, key_padding_mask)
v_unpad, _, _, _ = unpad_input(v, key_padding_mask)
else:
k_unpad = rearrange(k, "b s h d -> (b s) h d")
v_unpad = rearrange(v, "b s h d -> (b s) h d")
cu_seqlens_k = torch.arange(
0,
(batch_size + 1) * seqlen_k,
step=seqlen_k,
dtype=torch.int32,
device=k_unpad.device,
)
max_seqlen_k = seqlen_k
if qkvpacked:
assert nheads == nheads_k
qkv_unpad = torch.stack([q_unpad, k_unpad, v_unpad], dim=1)
qkv = torch.stack([q, k, v], dim=2)
return (qkv_unpad, cu_seqlens_q, max_seqlen_q, qkv, output_pad_fn)
if kvpacked:
kv_unpad = torch.stack([k_unpad, v_unpad], dim=1)
kv = torch.stack([k, v], dim=2)
return (
q_unpad,
kv_unpad,
cu_seqlens_q,
cu_seqlens_k,
max_seqlen_q,
max_seqlen_k,
q,
kv,
output_pad_fn,
)
return (
q_unpad,
k_unpad,
v_unpad,
cu_seqlens_q,
cu_seqlens_k,
max_seqlen_q,
max_seqlen_k,
q,
k,
v,
output_pad_fn,
)
def mistral_model_forward(
self,
input_ids: torch.LongTensor = None,
attention_mask: Optional[torch.Tensor] = None,
position_ids: Optional[torch.LongTensor] = None,
past_key_values: Optional[List[torch.FloatTensor]] = None,
inputs_embeds: Optional[torch.FloatTensor] = None,
use_cache: Optional[bool] = None,
output_attentions: Optional[bool] = None,
output_hidden_states: Optional[bool] = None,
return_dict: Optional[bool] = None,
) -> Union[Tuple, BaseModelOutputWithPast]:
output_attentions = (
output_attentions
if output_attentions is not None
else self.config.output_attentions
)
output_hidden_states = (
output_hidden_states
if output_hidden_states is not None
else self.config.output_hidden_states
)
use_cache = use_cache if use_cache is not None else self.config.use_cache
return_dict = (
return_dict if return_dict is not None else self.config.use_return_dict
)
# retrieve input_ids and inputs_embeds
if input_ids is not None and inputs_embeds is not None:
raise ValueError(
"You cannot specify both decoder_input_ids and decoder_inputs_embeds at the same time"
)
if input_ids is not None:
batch_size, seq_length = input_ids.shape
elif inputs_embeds is not None:
batch_size, seq_length, _ = inputs_embeds.shape
else:
raise ValueError(
"You have to specify either decoder_input_ids or decoder_inputs_embeds"
)
seq_length_with_past = seq_length
past_key_values_length = 0
if past_key_values is not None:
past_key_values_length = past_key_values[0][0].shape[2]
seq_length_with_past = seq_length_with_past + past_key_values_length
cu_seqlens = None
max_seqlen = None
if position_ids is None:
device = input_ids.device if input_ids is not None else inputs_embeds.device
position_ids = torch.arange(
past_key_values_length,
seq_length + past_key_values_length,
dtype=torch.long,
device=device,
)
position_ids = position_ids.unsqueeze(0).view(-1, seq_length)
else:
position_ids = position_ids.view(-1, seq_length).long()
cu_seqlens, max_seqlen = get_cu_seqlens_from_pos_ids(position_ids)
cu_seqlens = cu_seqlens.squeeze()
if inputs_embeds is None:
inputs_embeds = self.embed_tokens(input_ids)
# embed positions
if attention_mask is None:
attention_mask = torch.ones(
(batch_size, seq_length_with_past),
dtype=torch.bool,
device=inputs_embeds.device,
)
attention_mask = (
self._prepare_decoder_attention_mask( # pylint: disable=protected-access
attention_mask,
(batch_size, seq_length),
inputs_embeds,
past_key_values_length,
sliding_window=self.config.sliding_window,
)
)
hidden_states = inputs_embeds
if self.gradient_checkpointing and self.training:
if use_cache:
transformers.logger.warning_once(
"`use_cache=True` is incompatible with gradient checkpointing. Setting `use_cache=False`..."
)
use_cache = False
# decoder layers
all_hidden_states = () if output_hidden_states else None
all_self_attns = () if output_attentions else None
next_decoder_cache = () if use_cache else None
for idx, decoder_layer in enumerate(self.layers):
if output_hidden_states:
all_hidden_states += (hidden_states,)
past_key_value = past_key_values[idx] if past_key_values is not None else None
if self.gradient_checkpointing and self.training:
def create_custom_forward(module):
def custom_forward(*inputs):
# None for past_key_value
return module(*inputs)
return custom_forward
layer_outputs = torch.utils.checkpoint.checkpoint(
create_custom_forward(decoder_layer),
hidden_states,
attention_mask,
position_ids,
past_key_value,
output_attentions,
None,
cu_seqlens,
max_seqlen,
)
else:
layer_outputs = decoder_layer(
hidden_states,
attention_mask=attention_mask,
position_ids=position_ids,
past_key_value=past_key_value,
output_attentions=output_attentions,
use_cache=use_cache,
cu_seqlens=cu_seqlens,
max_seqlen=max_seqlen,
)
hidden_states = layer_outputs[0]
if use_cache:
next_decoder_cache += (layer_outputs[2 if output_attentions else 1],)
if output_attentions:
all_self_attns += (layer_outputs[1],)
hidden_states = self.norm(hidden_states)
# add hidden states from the last decoder layer
if output_hidden_states:
all_hidden_states += (hidden_states,)
next_cache = next_decoder_cache if use_cache else None
if not return_dict:
return tuple(
v
for v in [hidden_states, next_cache, all_hidden_states, all_self_attns]
if v is not None
)
return BaseModelOutputWithPast(
last_hidden_state=hidden_states,
past_key_values=next_cache,
hidden_states=all_hidden_states,
attentions=all_self_attns,
)
class MistralDecoderLayer(OriginalMistralDecoderLayer):
"""
patched version of MistralDecoderLayer to pass through the precalculated cu_seqlens
"""
def forward(
self,
hidden_states: torch.Tensor,
attention_mask: Optional[torch.Tensor] = None,
position_ids: Optional[torch.LongTensor] = None,
past_key_value: Optional[Tuple[torch.Tensor]] = None,
output_attentions: Optional[bool] = False,
use_cache: Optional[bool] = False,
cu_seqlens: Optional[torch.Tensor] = None,
max_seqlen: Optional[torch.Tensor] = None,
) -> Tuple[
torch.FloatTensor, Optional[Tuple[torch.FloatTensor, torch.FloatTensor]]
]:
"""
Args:
hidden_states (`torch.FloatTensor`): input to the layer of shape `(batch, seq_len, embed_dim)`
attention_mask (`torch.FloatTensor`, *optional*): attention mask of size
`(batch, 1, tgt_len, src_len)` where padding elements are indicated by very large negative values.
output_attentions (`bool`, *optional*):
Whether or not to return the attentions tensors of all attention layers. See `attentions` under
returned tensors for more detail.
use_cache (`bool`, *optional*):
If set to `True`, `past_key_values` key value states are returned and can be used to speed up decoding
(see `past_key_values`).
past_key_value (`Tuple(torch.FloatTensor)`, *optional*): cached past key and value projection states
cu_seqlens (`torch.Tensor`, *optional*) cumulative sequence len when packing
"""
residual = hidden_states
hidden_states = self.input_layernorm(hidden_states)
# Self Attention
hidden_states, self_attn_weights, present_key_value = self.self_attn(
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,
cu_seqlens=cu_seqlens,
max_seqlen=max_seqlen,
)
hidden_states = residual + hidden_states
# Fully Connected
residual = hidden_states
hidden_states = self.post_attention_layernorm(hidden_states)
hidden_states = self.mlp(hidden_states)
hidden_states = residual + hidden_states
outputs = (hidden_states,)
if output_attentions:
outputs += (self_attn_weights,)
if use_cache:
outputs += (present_key_value,)
return outputs
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