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# Copyright (c) Meta Platforms, Inc. and affiliates. | |
# | |
# This source code is licensed under the Apache License, Version 2.0 | |
# found in the LICENSE file in the root directory of this source tree. | |
# References: | |
# https://github.com/facebookresearch/dino/blob/master/vision_transformer.py | |
# https://github.com/rwightman/pytorch-image-models/tree/master/timm/models/vision_transformer.py | |
import logging | |
import os | |
import warnings | |
from torch import Tensor | |
from torch import nn | |
import torch | |
from torch.nn.functional import scaled_dot_product_attention | |
from torch.nn.attention import SDPBackend | |
XFORMERS_ENABLED = os.environ.get("XFORMERS_DISABLED") is None | |
try: | |
if XFORMERS_ENABLED: | |
from xformers.ops import memory_efficient_attention, unbind | |
XFORMERS_AVAILABLE = True | |
# warnings.warn("xFormers is available (Attention)") | |
else: | |
# warnings.warn("xFormers is disabled (Attention)") | |
raise ImportError | |
except ImportError: | |
XFORMERS_AVAILABLE = False | |
# warnings.warn("xFormers is not available (Attention)") | |
class Attention(nn.Module): | |
def __init__( | |
self, | |
dim: int, | |
num_heads: int = 8, | |
qkv_bias: bool = False, | |
proj_bias: bool = True, | |
attn_drop: float = 0.0, | |
proj_drop: float = 0.0, | |
) -> None: | |
super().__init__() | |
self.num_heads = num_heads | |
head_dim = dim // num_heads | |
self.scale = head_dim**-0.5 | |
self.qkv = nn.Linear(dim, dim * 3, bias=qkv_bias) | |
self.attn_drop = nn.Dropout(attn_drop) | |
self.proj = nn.Linear(dim, dim, bias=proj_bias) | |
self.proj_drop = nn.Dropout(proj_drop) | |
def forward(self, x: Tensor, attn_bias=None) -> Tensor: | |
B, N, C = x.shape | |
qkv = self.qkv(x).reshape(B, N, 3, self.num_heads, C // self.num_heads).permute(2, 0, 3, 1, 4) | |
q, k, v = qkv[0] * self.scale, qkv[1], qkv[2] | |
attn = q @ k.transpose(-2, -1) | |
attn = attn.softmax(dim=-1) | |
attn = self.attn_drop(attn) | |
x = (attn @ v).transpose(1, 2).reshape(B, N, C) | |
x = self.proj(x) | |
x = self.proj_drop(x) | |
return x | |
class MemEffAttention(Attention): | |
def forward(self, x: Tensor, attn_bias=None) -> Tensor: | |
if not XFORMERS_AVAILABLE: | |
if attn_bias is not None: | |
raise AssertionError("xFormers is required for using nested tensors") | |
return super().forward(x) | |
B, N, C = x.shape | |
qkv = self.qkv(x).reshape(B, N, 3, self.num_heads, C // self.num_heads) | |
# q, k, v = unbind(qkv, 2) | |
q, k, v = [qkv[:,:,i] for i in range(3)] | |
x = memory_efficient_attention(q, k, v, attn_bias=attn_bias) | |
x = x.reshape([B, N, C]) | |
x = self.proj(x) | |
x = self.proj_drop(x) | |
return x | |
class FlashAttention(Attention): | |
def forward(self, x: Tensor, attn_bias=None) -> Tensor: | |
B, N, C = x.shape | |
qkv = self.qkv(x).reshape(B, N, 3, self.num_heads, C // self.num_heads).transpose(1, 3) | |
# q, k, v = unbind(qkv, 2) | |
q, k, v = [qkv[:,:,i] for i in range(3)] | |
if q.dtype == torch.bfloat16: | |
with nn.attention.sdpa_kernel(SDPBackend.FLASH_ATTENTION): | |
x = scaled_dot_product_attention(q, k, v) | |
else: | |
with nn.attention.sdpa_kernel([SDPBackend.MATH, SDPBackend.EFFICIENT_ATTENTION]): | |
x = scaled_dot_product_attention(q, k, v) | |
x = x.transpose(1, 2).reshape([B, N, C]) | |
x = self.proj(x) | |
x = self.proj_drop(x) | |
return x | |
""" | |
Following is written by GPT-4o | |
""" | |
class CrossAttentionRope(nn.Module): | |
def __init__( | |
self, | |
dim: int, | |
num_heads: int = 8, | |
qkv_bias: bool = False, | |
proj_bias: bool = True, | |
attn_drop: float = 0.0, | |
proj_drop: float = 0.0, | |
qk_norm: bool = False, | |
norm_layer: nn.Module = nn.LayerNorm, | |
rope=None, | |
) -> None: | |
super().__init__() | |
self.num_heads = num_heads | |
head_dim = dim // num_heads | |
self.scale = head_dim**-0.5 | |
# Separate projection layers for query, key, and value | |
self.q_proj = nn.Linear(dim, dim, bias=qkv_bias) | |
self.k_proj = nn.Linear(dim, dim, bias=qkv_bias) | |
self.v_proj = nn.Linear(dim, dim, bias=qkv_bias) | |
self.q_norm = norm_layer(head_dim) if qk_norm else nn.Identity() | |
self.k_norm = norm_layer(head_dim) if qk_norm else nn.Identity() | |
self.attn_drop = nn.Dropout(attn_drop) | |
self.proj = nn.Linear(dim, dim, bias=proj_bias) | |
self.proj_drop = nn.Dropout(proj_drop) | |
self.rope = rope | |
def forward(self, query: Tensor, key: Tensor, value: Tensor, attn_bias=None, qpos=None, kpos=None) -> Tensor: | |
""" | |
Args: | |
query: Tensor of shape (B, N, C), input query | |
key: Tensor of shape (B, M, C), input key | |
value: Tensor of shape (B, M, C), input value | |
attn_bias: Optional tensor for attention bias | |
Returns: | |
Tensor of shape (B, N, C), output of cross-attention | |
""" | |
B, N, C = query.shape | |
_, M, _ = key.shape | |
# Project query, key, and value | |
q = self.q_proj(query).reshape(B, N, self.num_heads, C // self.num_heads).permute(0, 2, 1, 3) | |
k = self.k_proj(key).reshape(B, M, self.num_heads, C // self.num_heads).permute(0, 2, 1, 3) | |
v = self.v_proj(value).reshape(B, M, self.num_heads, C // self.num_heads).permute(0, 2, 1, 3) | |
q, k = self.q_norm(q).to(v.dtype), self.k_norm(k).to(v.dtype) | |
if self.rope is not None: | |
q = self.rope(q, qpos) | |
k = self.rope(k, kpos) | |
# Scale query | |
q = q * self.scale | |
# Compute attention scores | |
attn = q @ k.transpose(-2, -1) # (B, num_heads, N, M) | |
if attn_bias is not None: | |
attn = attn + attn_bias | |
attn = attn.softmax(dim=-1) | |
attn = self.attn_drop(attn) | |
# Compute attention output | |
x = (attn @ v).transpose(1, 2).reshape(B, N, C) # (B, N, C) | |
# Final projection | |
x = self.proj(x) | |
x = self.proj_drop(x) | |
return x | |
class MemEffCrossAttentionRope(CrossAttentionRope): | |
def forward(self, query: Tensor, key: Tensor, value: Tensor, attn_bias=None, qpos=None, kpos=None) -> Tensor: | |
""" | |
Args: | |
query: Tensor of shape (B, N, C), input query | |
key: Tensor of shape (B, M, C), input key | |
value: Tensor of shape (B, M, C), input value | |
attn_bias: Optional tensor for attention bias | |
Returns: | |
Tensor of shape (B, N, C), output of cross-attention | |
""" | |
if not XFORMERS_AVAILABLE: | |
if attn_bias is not None: | |
raise AssertionError("xFormers is required for using nested tensors") | |
return super().forward(query, key, value, attn_bias) | |
B, N, C = query.shape | |
_, M, _ = key.shape | |
# Project query, key, and value | |
q = self.q_proj(query).reshape(B, N, self.num_heads, C // self.num_heads) | |
k = self.k_proj(key).reshape(B, M, self.num_heads, C // self.num_heads) | |
v = self.v_proj(value).reshape(B, M, self.num_heads, C // self.num_heads) | |
q = q.transpose(1, 2) | |
k = k.transpose(1, 2) | |
q, k = self.q_norm(q).to(v.dtype), self.k_norm(k).to(v.dtype) | |
if self.rope is not None: | |
q = self.rope(q, qpos) | |
k = self.rope(k, kpos) | |
q = q.transpose(1, 2) | |
k = k.transpose(1, 2) | |
# Compute memory-efficient attention | |
x = memory_efficient_attention(q, k, v, attn_bias=attn_bias) | |
x = x.reshape(B, N, C) | |
# Final projection | |
x = self.proj(x) | |
x = self.proj_drop(x) | |
return x | |
class AttentionRope(nn.Module): | |
def __init__( | |
self, | |
dim: int, | |
num_heads: int = 8, | |
qkv_bias: bool = False, | |
proj_bias: bool = True, | |
attn_drop: float = 0.0, | |
proj_drop: float = 0.0, | |
qk_norm: bool = False, | |
norm_layer: nn.Module = nn.LayerNorm, | |
rope=None | |
) -> None: | |
super().__init__() | |
self.num_heads = num_heads | |
head_dim = dim // num_heads | |
self.scale = head_dim**-0.5 | |
self.qkv = nn.Linear(dim, dim * 3, bias=qkv_bias) | |
self.attn_drop = nn.Dropout(attn_drop) | |
self.proj = nn.Linear(dim, dim, bias=proj_bias) | |
self.proj_drop = nn.Dropout(proj_drop) | |
self.q_norm = norm_layer(head_dim) if qk_norm else nn.Identity() | |
self.k_norm = norm_layer(head_dim) if qk_norm else nn.Identity() | |
self.rope = rope | |
def forward(self, x: Tensor, attn_bias=None, xpos=None) -> Tensor: | |
B, N, C = x.shape | |
qkv = self.qkv(x).reshape(B, N, 3, self.num_heads, C // self.num_heads).permute(2, 0, 3, 1, 4) | |
q, k, v = qkv[0], qkv[1], qkv[2] | |
q, k = self.q_norm(q).to(v.dtype), self.k_norm(k).to(v.dtype) | |
if self.rope is not None: | |
q = self.rope(q, xpos) | |
k = self.rope(k, xpos) | |
q = q * self.scale | |
attn = q @ k.transpose(-2, -1) | |
attn = attn.softmax(dim=-1) | |
attn = self.attn_drop(attn) | |
x = (attn @ v).transpose(1, 2).reshape(B, N, C) | |
x = self.proj(x) | |
x = self.proj_drop(x) | |
return x | |
class MemEffAttentionRope(AttentionRope): | |
def forward(self, x: Tensor, attn_bias=None, xpos=None) -> Tensor: | |
if not XFORMERS_AVAILABLE: | |
if attn_bias is not None: | |
raise AssertionError("xFormers is required for using nested tensors") | |
return super().forward(x) | |
B, N, C = x.shape | |
qkv = self.qkv(x).reshape(B, N, 3, self.num_heads, C // self.num_heads) | |
qkv = qkv.transpose(1, 3) | |
# q, k, v = unbind(qkv, 2) | |
q, k, v = [qkv[:,:,i] for i in range(3)] | |
q, k = self.q_norm(q).to(v.dtype), self.k_norm(k).to(v.dtype) | |
if self.rope is not None: | |
q = self.rope(q, xpos) | |
k = self.rope(k, xpos) | |
q = q.transpose(1, 2) | |
k = k.transpose(1, 2) | |
v = v.transpose(1, 2) | |
x = memory_efficient_attention(q, k, v, attn_bias=attn_bias) | |
x = x.reshape([B, N, C]) | |
# score_matrix = (q.permute(0, 2, 1, 3) * self.scale @ k.permute(0, 2, 1, 3).transpose(-2, -1)).sum(dim=1).reshape(frame_num, 261, frame_num, 261).mean(dim=[1, 3]).sum(1) # for frame attention matrix | |
# global_valid_id = torch.where(score_matrix > 0) | |
# score_matrix = (q.permute(0, 2, 1, 3) * self.scale @ k.permute(0, 2, 1, 3).transpose(-2, -1)).sum(dim=1) | |
x = self.proj(x) | |
x = self.proj_drop(x) | |
return x | |
class FlashAttentionRope(AttentionRope): | |
def forward(self, x: Tensor, attn_bias=None, xpos=None) -> Tensor: | |
B, N, C = x.shape | |
qkv = self.qkv(x).reshape(B, N, 3, self.num_heads, C // self.num_heads).transpose(1, 3) | |
# q, k, v = unbind(qkv, 2) | |
q, k, v = [qkv[:,:,i] for i in range(3)] | |
q, k = self.q_norm(q).to(v.dtype), self.k_norm(k).to(v.dtype) | |
if self.rope is not None: | |
q = self.rope(q, xpos) | |
k = self.rope(k, xpos) | |
if q.dtype == torch.bfloat16: | |
with nn.attention.sdpa_kernel(SDPBackend.FLASH_ATTENTION): | |
x = scaled_dot_product_attention(q, k, v) | |
else: | |
with nn.attention.sdpa_kernel([SDPBackend.MATH, SDPBackend.EFFICIENT_ATTENTION]): | |
x = scaled_dot_product_attention(q, k, v) | |
x = x.transpose(1, 2).reshape([B, N, C]) | |
x = self.proj(x) | |
x = self.proj_drop(x) | |
return x | |
def get_attn_score(blk_class, x, frame_num, token_length, xpos=None): | |
x = blk_class.norm1(x) | |
B, N, C = x.shape | |
qkv = blk_class.attn.qkv(x).reshape(B, N, 3, blk_class.attn.num_heads, C // blk_class.attn.num_heads) | |
qkv = qkv.transpose(1, 3) | |
# q, k, v = unbind(qkv, 2) | |
q, k, v = [qkv[:,:,i] for i in range(3)] | |
q, k = blk_class.attn.q_norm(q).to(v.dtype), blk_class.attn.k_norm(k).to(v.dtype) | |
if blk_class.attn.rope is not None: | |
q = blk_class.attn.rope(q, xpos) | |
k = blk_class.attn.rope(k, xpos) | |
q = q.transpose(1, 2) | |
k = k.transpose(1, 2) | |
score = (q.permute(0, 2, 1, 3) * blk_class.attn.scale @ k.permute(0, 2, 1, 3).transpose(-2, -1)).sum(dim=1).reshape(B, frame_num, token_length, frame_num, token_length).mean(dim=[2, 4]).sum(-1) | |
return score |