yolov26改进 | 添加注意力机制篇 | 实现级联群体注意力机制CGAttention改进C2PSA机制 (含独家网络结构图)
开始讲解之前推荐一下我的专栏,本专栏的内容支持(分类、检测、分割、追踪、关键点检测),专栏目前为限时折扣,欢迎大家订阅本专栏,本专栏每周更新5-7篇最新机制,更有包含我所有改进的文件和交流群提供给大家,本人定期在群内分享发表论文方法和经验。
一、本文介绍
本文给大家带来的改进机制是实现级联群体注意力机制CascadedGroupAttention,其主要思想为增强输入到注意力头的特征的多样性。与以前的自注意力不同,它为每个头提供不同的输入分割,并跨头级联输出特征。这种方法不仅减少了多头注意力中的计算冗余,而且通过增加网络深度来提升模型容量,亲测在我的25个类别的数据上,大部分的类别均有一定的涨点效果,仅有部分的类别保持不变,同时给该注意力机制含有二次创新的机会
欢迎大家订阅我的专栏一起学习YOLO!

专栏链接:YOLOv26有效涨点专栏包含:Conv、注意力机制、主干/Backbone、损失函数、优化器、后处理等改进机制
目录
二、 CascadedGroupAttention的基本原理
二、 CascadedGroupAttention的基本原理
官方论文地址: 官方论文地址点击即可跳转
官方代码地址: 官方代码地址点击即可跳转
Cascaded Group Attention (CGA) 是在文章 "EfficientViT: Memory Efficient Vision Transformer with Cascaded Group Attention" 中提出的一种新型注意力机制。其核心思想是增强输入到注意力头的特征的多样性。与以前的自注意力不同,它为每个头提供不同的输入分割,并跨头级联输出特征。这种方法不仅减少了多头注意力中的计算冗余,而且通过增加网络深度来提升模型容量。
具体来说,CGA 将输入特征分成不同的部分,每部分输入到一个注意力头。每个头计算其自注意力映射,然后将所有头的输出级联起来,并通过一个线性层将它们投影回输入的维度。通过这样的方式,CGA 在不增加额外参数的情况下提高了模型的计算效率。另外,通过串联的方式,每个头的输出都会添加到下一个头的输入中,从而逐步精化特征表示。
Cascaded Group Attention 的优点包括:
1. 提高了注意力图的多样性。
2. 减少了计算冗余,因为它减少了 QKV 层中输入和输出通道的数量。
3. 增加了网络深度,从而进一步提高了模型容量,同时只增加了很小的延迟开销,因为每个头的 QK 通道维度较小。
这张图描绘了 "EfficientViT" 模型中 "Cascaded Group Attention" (CGA) 模块的架构。
CGA模块位于图中的(c)部分,可以看到它的作用是处理输入特征,并提供分级的注意力机制。在这个模块中,输入首先被分割成多个部分,每个部分对应一个注意力头。每个头独立地计算其自注意力,并产生一个输出。然后,所有头的输出被级联(concatenate)在一起,通过一个线性投影层形成最终的输出。这种设计允许模型在不同的层次上捕捉特征,通过级联增强了特征之间的交互,同时提高了计算效率。
级联组注意力的关键点在于每个注意力头只关注输入的一部分,然后把所有头的注意力合并起来,来获取一个全面的特征表示。这样做的好处是减少了计算重复并增加了注意力的多样性,因为不同的头可能会关注输入的不同方面。这种方法提高了模型的内存和计算效率,同时保持或增强模型的性能。
三、CGA的核心代码
代码使用方式看章节四!
# https://github.com/microsoft/Cream/blob/ef68993c764f241a768cd69a087ed567dec6cb40/EfficientViT/classification/model/efficientvit.py#L104-L181
import itertools
import torch
from torch import nn
__all__ = ['C2PSA_CGA', 'LocalWindowAttention']
class Conv2d_BN(torch.nn.Sequential):
def __init__(self, a, b, ks=1, stride=1, pad=0, dilation=1,
groups=1, bn_weight_init=1, resolution=-10000):
super().__init__()
self.add_module('c', torch.nn.Conv2d(
a, b, ks, stride, pad, dilation, groups, bias=False))
self.add_module('bn', torch.nn.BatchNorm2d(b))
torch.nn.init.constant_(self.bn.weight, bn_weight_init)
torch.nn.init.constant_(self.bn.bias, 0)
@torch.no_grad()
def switch_to_deploy(self):
c, bn = self._modules.values()
w = bn.weight / (bn.running_var + bn.eps)**0.5
w = c.weight * w[:, None, None, None]
b = bn.bias - bn.running_mean * bn.weight / \
(bn.running_var + bn.eps)**0.5
m = torch.nn.Conv2d(w.size(1) * self.c.groups, w.size(
0), w.shape[2:], stride=self.c.stride, padding=self.c.padding, dilation=self.c.dilation, groups=self.c.groups)
m.weight.data.copy_(w)
m.bias.data.copy_(b)
return m
class CascadedGroupAttention(torch.nn.Module):
r""" Cascaded Group Attention.
Args:
dim (int): Number of input channels.
key_dim (int): The dimension for query and key.
num_heads (int): Number of attention heads.
attn_ratio (int): Multiplier for the query dim for value dimension.
resolution (int): Input resolution, correspond to the window size.
kernels (List[int]): The kernel size of the dw conv on query.
"""
def __init__(self, dim, key_dim, num_heads=8,
attn_ratio=4,
resolution=14,
kernels=[5, 5, 5, 5], ):
super().__init__()
self.num_heads = num_heads
self.scale = key_dim ** -0.5
self.key_dim = key_dim
self.d = int(attn_ratio * key_dim)
self.attn_ratio = attn_ratio
qkvs = []
dws = []
for i in range(num_heads):
qkvs.append(Conv2d_BN(dim // (num_heads), self.key_dim * 2 + self.d, resolution=resolution))
dws.append(Conv2d_BN(self.key_dim, self.key_dim, kernels[i], 1, kernels[i] // 2, groups=self.key_dim,
resolution=resolution))
self.qkvs = torch.nn.ModuleList(qkvs)
self.dws = torch.nn.ModuleList(dws)
self.proj = torch.nn.Sequential(torch.nn.ReLU(), Conv2d_BN(
self.d * num_heads, dim, bn_weight_init=0, resolution=resolution))
points = list(itertools.product(range(resolution), range(resolution)))
N = len(points)
attention_offsets = {}
idxs = []
for p1 in points:
for p2 in points:
offset = (abs(p1[0] - p2[0]), abs(p1[1] - p2[1]))
if offset not in attention_offsets:
attention_offsets[offset] = len(attention_offsets)
idxs.append(attention_offsets[offset])
self.attention_biases = torch.nn.Parameter(
torch.zeros(num_heads, len(attention_offsets)))
self.register_buffer('attention_bias_idxs',
torch.LongTensor(idxs).view(N, N))
@torch.no_grad()
def train(self, mode=True):
super().train(mode)
if mode and hasattr(self, 'ab'):
del self.ab
else:
self.ab = self.attention_biases[:, self.attention_bias_idxs]
def forward(self, x): # x (B,C,H,W)
B, C, H, W = x.shape
trainingab = self.attention_biases[:, self.attention_bias_idxs]
feats_in = x.chunk(len(self.qkvs), dim=1)
feats_out = []
feat = feats_in[0]
for i, qkv in enumerate(self.qkvs):
if i > 0: # add the previous output to the input
feat = feat + feats_in[i]
feat = qkv(feat)
q, k, v = feat.view(B, -1, H, W).split([self.key_dim, self.key_dim, self.d], dim=1) # B, C/h, H, W
q = self.dws[i](q)
q, k, v = q.flatten(2), k.flatten(2), v.flatten(2) # B, C/h, N
attn = (
(q.transpose(-2, -1) @ k) * self.scale
+
(trainingab[i] if self.training else self.ab[i])
)
attn = attn.softmax(dim=-1) # BNN
feat = (v @ attn.transpose(-2, -1)).view(B, self.d, H, W) # BCHW
feats_out.append(feat)
x = self.proj(torch.cat(feats_out, 1))
return x
class LocalWindowAttention(torch.nn.Module):
r""" Local Window Attention.
Args:
dim (int): Number of input channels.
key_dim (int): The dimension for query and key.
num_heads (int): Number of attention heads.
attn_ratio (int): Multiplier for the query dim for value dimension.
resolution (int): Input resolution.
window_resolution (int): Local window resolution.
kernels (List[int]): The kernel size of the dw conv on query.
"""
def __init__(self, dim, num_heads=4,
attn_ratio=4,
resolution=14,
window_resolution=7,
kernels=[5, 5, 5, 5], ):
super().__init__()
key_dim = dim // 16 # 必须放缩16倍否则会报错
self.dim = dim
self.num_heads = num_heads
self.resolution = resolution
assert window_resolution > 0, 'window_size must be greater than 0'
self.window_resolution = window_resolution
self.attn = CascadedGroupAttention(dim, key_dim, num_heads,
attn_ratio=attn_ratio,
resolution=window_resolution,
kernels=kernels, )
def forward(self, x):
B, C, H, W = x.shape
if H <= self.window_resolution and W <= self.window_resolution:
x = self.attn(x)
else:
x = x.permute(0, 2, 3, 1)
pad_b = (self.window_resolution - H %
self.window_resolution) % self.window_resolution
pad_r = (self.window_resolution - W %
self.window_resolution) % self.window_resolution
padding = pad_b > 0 or pad_r > 0
if padding:
x = torch.nn.functional.pad(x, (0, 0, 0, pad_r, 0, pad_b))
pH, pW = H + pad_b, W + pad_r
nH = pH // self.window_resolution
nW = pW // self.window_resolution
# window partition, BHWC -> B(nHh)(nWw)C -> BnHnWhwC -> (BnHnW)hwC -> (BnHnW)Chw
x = x.view(B, nH, self.window_resolution, nW, self.window_resolution, C).transpose(2, 3).reshape(
B * nH * nW, self.window_resolution, self.window_resolution, C
).permute(0, 3, 1, 2)
x = self.attn(x)
# window reverse, (BnHnW)Chw -> (BnHnW)hwC -> BnHnWhwC -> B(nHh)(nWw)C -> BHWC
x = x.permute(0, 2, 3, 1).view(B, nH, nW, self.window_resolution, self.window_resolution,
C).transpose(2, 3).reshape(B, pH, pW, C)
if padding:
x = x[:, :H, :W].contiguous()
x = x.permute(0, 3, 1, 2)
return x
def autopad(k, p=None, d=1): # kernel, padding, dilation
"""Pad to 'same' shape outputs."""
if d > 1:
k = d * (k - 1) + 1 if isinstance(k, int) else [d * (x - 1) + 1 for x in k] # actual kernel-size
if p is None:
p = k // 2 if isinstance(k, int) else [x // 2 for x in k] # auto-pad
return p
class Conv(nn.Module):
"""Standard convolution with args(ch_in, ch_out, kernel, stride, padding, groups, dilation, activation)."""
default_act = nn.SiLU() # default activation
def __init__(self, c1, c2, k=1, s=1, p=None, g=1, d=1, act=True):
"""Initialize Conv layer with given arguments including activation."""
super().__init__()
self.conv = nn.Conv2d(c1, c2, k, s, autopad(k, p, d), groups=g, dilation=d, bias=False)
self.bn = nn.BatchNorm2d(c2)
self.act = self.default_act if act is True else act if isinstance(act, nn.Module) else nn.Identity()
def forward(self, x):
"""Apply convolution, batch normalization and activation to input tensor."""
return self.act(self.bn(self.conv(x)))
def forward_fuse(self, x):
"""Perform transposed convolution of 2D data."""
return self.act(self.conv(x))
class PSABlock(nn.Module):
"""
PSABlock class implementing a Position-Sensitive Attention block for neural networks.
This class encapsulates the functionality for applying multi-head attention and feed-forward neural network layers
with optional shortcut connections.
Attributes:
attn (Attention): Multi-head attention module.
ffn (nn.Sequential): Feed-forward neural network module.
add (bool): Flag indicating whether to add shortcut connections.
Methods:
forward: Performs a forward pass through the PSABlock, applying attention and feed-forward layers.
Examples:
Create a PSABlock and perform a forward pass
"""
def __init__(self, c, attn_ratio=0.5, num_heads=4, shortcut=True) -> None:
"""Initializes the PSABlock with attention and feed-forward layers for enhanced feature extraction."""
super().__init__()
self.attn = LocalWindowAttention(c)
self.ffn = nn.Sequential(Conv(c, c * 2, 1), Conv(c * 2, c, 1, act=False))
self.add = shortcut
def forward(self, x):
"""Executes a forward pass through PSABlock, applying attention and feed-forward layers to the input tensor."""
x = x + self.attn(x) if self.add else self.attn(x)
x = x + self.ffn(x) if self.add else self.ffn(x)
return x
class C2PSA_CGA(nn.Module):
"""
C2PSA module with attention mechanism for enhanced feature extraction and processing.
This module implements a convolutional block with attention mechanisms to enhance feature extraction and processing
capabilities. It includes a series of PSABlock modules for self-attention and feed-forward operations.
Attributes:
c (int): Number of hidden channels.
cv1 (Conv): 1x1 convolution layer to reduce the number of input channels to 2*c.
cv2 (Conv): 1x1 convolution layer to reduce the number of output channels to c.
m (nn.Sequential): Sequential container of PSABlock modules for attention and feed-forward operations.
Methods:
forward: Performs a forward pass through the C2PSA module, applying attention and feed-forward operations.
Notes:
This module essentially is the same as PSA module, but refactored to allow stacking more PSABlock modules.
Examples:
"""
def __init__(self, c1, c2, n=1, e=0.5):
"""Initializes the C2PSA module with specified input/output channels, number of layers, and expansion ratio."""
super().__init__()
assert c1 == c2
self.c = int(c1 * e)
self.cv1 = Conv(c1, 2 * self.c, 1, 1)
self.cv2 = Conv(2 * self.c, c1, 1)
self.m = nn.Sequential(*(PSABlock(self.c, attn_ratio=0.5, num_heads=self.c // 64) for _ in range(n)))
def forward(self, x):
"""Processes the input tensor 'x' through a series of PSA blocks and returns the transformed tensor."""
a, b = self.cv1(x).split((self.c, self.c), dim=1)
b = self.m(b)
return self.cv2(torch.cat((a, b), 1))
if __name__ == "__main__":
# Generating Sample image
image_size = (1, 64, 224, 224)
image = torch.rand(*image_size)
# Model
model = C2PSA_CGA(64, 64)
out = model(image)
print(out.size())
四、CGA的添加方式
下面的步骤如果你不会或者不想麻烦操作,可以联系作者获得本专栏添加所有项目文件的源代码,可直接训练.
4.1 修改一
第一还是建立文件,我们找到如下ultralytics/nn文件夹下建立一个目录名字呢就是'Addmodules'文件夹!

4.2 修改二
然后在Addmodules文件夹内建立一个新的py文件,将本文章节三中的“核心代码"复制粘贴进去。

4.3 修改三
第二步我们在该目录下创建一个新的py文件名字为'__init__.py',然后在其内部导入我们的文件,如下图所示。
4.4 修改四
第三步我门中到如下文件'ultralytics/nn/tasks.py'进行导入和注册我们的模块(此处只需要添加一次即可,如果你用我其它的改进机制这里的步骤只需要添加一次)!
4.5 修改五
在'ultralytics/nn/tasks.py'文件内的parse_model方法函数内(位置大概在1500+行左右),按照图示位置添加即可(此处需要自己有一定的判别能力,如果不会可联系作者获得视频教程)。
4.6 修改六
在'ultralytics/nn/tasks.py'文件内的parse_model方法函数内(位置大概在1550+行左右),按照图示位置添加即可,此处一定要对应好位置和缩进否则很容易报错。

elif m in {此处填写本章代码的名字.}:
c2 = ch[f]
args = [c2, *args]
五、正式训练
5.1 yaml文件
5.1.1 yaml文件1
训练信息:YOLO26-C2PSA-CGA summary: 271 layers, 2,479,040 parameters, 2,479,040 gradients, 5.8 GFLOPs
# Ultralytics 🚀 AGPL-3.0 License - https://ultralytics.com/license
# Ultralytics YOLO26 object detection model with P3/8 - P5/32 outputs
# Model docs: https://docs.ultralytics.com/models/yolo26
# Task docs: https://docs.ultralytics.com/tasks/detect
# Parameters
nc: 80 # number of classes
end2end: True # whether to use end-to-end mode
reg_max: 1 # DFL bins
scales: # model compound scaling constants, i.e. 'model=yolo26n.yaml' will call yolo26.yaml with scale 'n'
# [depth, width, max_channels]
n: [0.50, 0.25, 1024] # summary: 260 layers, 2,572,280 parameters, 2,572,280 gradients, 6.1 GFLOPs
s: [0.50, 0.50, 1024] # summary: 260 layers, 10,009,784 parameters, 10,009,784 gradients, 22.8 GFLOPs
m: [0.50, 1.00, 512] # summary: 280 layers, 21,896,248 parameters, 21,896,248 gradients, 75.4 GFLOPs
l: [1.00, 1.00, 512] # summary: 392 layers, 26,299,704 parameters, 26,299,704 gradients, 93.8 GFLOPs
x: [1.00, 1.50, 512] # summary: 392 layers, 58,993,368 parameters, 58,993,368 gradients, 209.5 GFLOPs
# YOLO26n backbone
backbone:
# [from, repeats, module, args]
- [-1, 1, Conv, [64, 3, 2]] # 0-P1/2
- [-1, 1, Conv, [128, 3, 2]] # 1-P2/4
- [-1, 2, C3k2, [256, False, 0.25]]
- [-1, 1, Conv, [256, 3, 2]] # 3-P3/8
- [-1, 2, C3k2, [512, False, 0.25]]
- [-1, 1, Conv, [512, 3, 2]] # 5-P4/16
- [-1, 2, C3k2, [512, True]]
- [-1, 1, Conv, [1024, 3, 2]] # 7-P5/32
- [-1, 2, C3k2, [1024, True]]
- [-1, 1, SPPF, [1024, 5, 3, True]] # 9
- [-1, 2, C2PSA_CGA, [1024]] # 10
# YOLO26n head
head:
- [-1, 1, nn.Upsample, [None, 2, "nearest"]]
- [[-1, 6], 1, Concat, [1]] # cat backbone P4
- [-1, 2, C3k2, [512, True]] # 13
- [-1, 1, nn.Upsample, [None, 2, "nearest"]]
- [[-1, 4], 1, Concat, [1]] # cat backbone P3
- [-1, 2, C3k2, [256, True]] # 16 (P3/8-small)
- [-1, 1, Conv, [256, 3, 2]]
- [[-1, 13], 1, Concat, [1]] # cat head P4
- [-1, 2, C3k2, [512, True]] # 19 (P4/16-medium)
- [-1, 1, Conv, [512, 3, 2]]
- [[-1, 10], 1, Concat, [1]] # cat head P5
- [-1, 1, C3k2, [1024, True, 0.5, True]] # 22 (P5/32-large)
- [[16, 19, 22], 1, Detect, [nc]] # Detect(P3, P4, P5)
5.1.2 yaml文件2
训练信息:YOLO26-Att-CGA summary: 279 layers, 2,512,720 parameters, 2,512,720 gradients, 5.9 GFLOPs
# Ultralytics 🚀 AGPL-3.0 License - https://ultralytics.com/license
# Ultralytics YOLO26 object detection model with P3/8 - P5/32 outputs
# Model docs: https://docs.ultralytics.com/models/yolo26
# Task docs: https://docs.ultralytics.com/tasks/detect
# Parameters
nc: 80 # number of classes
end2end: True # whether to use end-to-end mode
reg_max: 1 # DFL bins
scales: # model compound scaling constants, i.e. 'model=yolo26n.yaml' will call yolo26.yaml with scale 'n'
# [depth, width, max_channels]
n: [0.50, 0.25, 1024] # summary: 260 layers, 2,572,280 parameters, 2,572,280 gradients, 6.1 GFLOPs
s: [0.50, 0.50, 1024] # summary: 260 layers, 10,009,784 parameters, 10,009,784 gradients, 22.8 GFLOPs
m: [0.50, 1.00, 512] # summary: 280 layers, 21,896,248 parameters, 21,896,248 gradients, 75.4 GFLOPs
l: [1.00, 1.00, 512] # summary: 392 layers, 26,299,704 parameters, 26,299,704 gradients, 93.8 GFLOPs
x: [1.00, 1.50, 512] # summary: 392 layers, 58,993,368 parameters, 58,993,368 gradients, 209.5 GFLOPs
# YOLO26n backbone
backbone:
# [from, repeats, module, args]
- [-1, 1, Conv, [64, 3, 2]] # 0-P1/2
- [-1, 1, Conv, [128, 3, 2]] # 1-P2/4
- [-1, 2, C3k2, [256, False, 0.25]]
- [-1, 1, Conv, [256, 3, 2]] # 3-P3/8
- [-1, 2, C3k2, [512, False, 0.25]]
- [-1, 1, Conv, [512, 3, 2]] # 5-P4/16
- [-1, 2, C3k2, [512, True]]
- [-1, 1, Conv, [1024, 3, 2]] # 7-P5/32
- [-1, 2, C3k2, [1024, True]]
- [-1, 1, SPPF, [1024, 5, 3, True]] # 9
- [-1, 2, C2PSA, [1024]] # 10
# YOLO26n head
head:
- [-1, 1, nn.Upsample, [None, 2, "nearest"]]
- [[-1, 6], 1, Concat, [1]] # cat backbone P4
- [-1, 2, C3k2, [512, True]] # 13
- [-1, 1, nn.Upsample, [None, 2, "nearest"]]
- [[-1, 4], 1, Concat, [1]] # cat backbone P3
- [-1, 2, C3k2, [256, True]] # 16 (P3/8-small)
- [-1, 1, Conv, [256, 3, 2]]
- [[-1, 13], 1, Concat, [1]] # cat head P4
- [-1, 2, C3k2, [512, True]] # 19 (P4/16-medium)
- [-1, 1, Conv, [512, 3, 2]]
- [[-1, 10], 1, Concat, [1]] # cat head P5
- [-1, 1, C3k2, [1024, True, 0.5, True]] # 22 (P5/32-large)
- [16, 1, LocalWindowAttention, []] # 23
# - [19, 1, LocalWindowAttention, []] # 24
# - [22, 1, LocalWindowAttention, []] # 25
# 此处的使用说法注释: 其中上面的三个注意力机制目前仅使用了23层,如果你想使用24层那么就取消掉代码注释,
# 并将下面检测头中的19改为24,如果想使用第25层注意力机制同理,将下面检测头中的22改为25即可。
# 此处用法比较复杂如过不会联系Snu77博主获取视频教程
- [[23, 19, 22], 1, Detect, [nc]] # Detect(P3, P4, P5)
5.2 训练代码
大家可以创建一个py文件将我给的代码复制粘贴进去,配置好自己的文件路径即可运行。
import warnings
warnings.filterwarnings('ignore')
from ultralytics import YOLO
if __name__ == '__main__':
model = YOLO('模型配置文件地址,也就是5.1你保存到本地文件的地址')
# 如何切换模型版本, 上面的ymal文件可以改为 yolo26s.yaml就是使用的26s,
# 类似某个改进的yaml文件名称为yolo26-XXX.yaml那么如果想使用其它版本就把上面的名称改为yolo26l-XXX.yaml即可(改的是上面YOLO中间的名字不是配置文件的)!
# model.load('yolo26n.pt') # 是否加载预训练权重,科研不建议大家加载否则很难提升精度
model.train(
data=r"数据集文件地址",
# 如果大家任务是其它的'ultralytics/cfg/default.yaml'找到这里修改task可以改成detect, segment, classify, pose
cache=False,
imgsz=640,
epochs=20,
single_cls=False, # 是否是单类别检测
batch=16,
close_mosaic=0,
workers=0,
device='0',
optimizer='MuSGD', # using SGD/MuSGD
# resume=, # 这里是填写last.pt地址
amp=True, # 如果出现训练损失为Nan可以关闭amp
project='runs/train',
name='exp',
)
5.3 训练过程截图
五、本文总结
到此本文的正式分享内容就结束了,在这里给大家推荐我的YOLOv26改进有效涨点专栏,本专栏目前为新开的平均质量分98分,后期我会根据各种最新的前沿顶会进行论文复现,也会对一些老的改进机制进行补充,如果大家觉得本文帮助到你了,订阅本专栏,关注后续更多的更新~
专栏链接:YOLOv26有效涨点专栏包含:Conv、注意力机制、主干/Backbone、损失函数、优化器、后处理等改进机制