目标检测算法改进系列之添加SCConv空间和通道重构卷积

SCConv-空间和通道重构卷积

SCConv（空间和通道重构卷积）的高效卷积模块，以减少卷积神经网络（CNN）中的空间和通道冗余。SCConv旨在通过优化特征提取过程，减少计算资源消耗并提高网络性能。该模块包括两个单元：
1.空间重构单元（SRU）：SRU通过分离和重构方法来减少空间冗余。
2.通道重构单元（CRU）：CRU采用分割-变换-融合策略来减少通道冗余。

论文地址：SCConv: Spatial and Channel Reconstruction Convolution for Feature Redundancy

YOLOv8添加SCConv卷积

SCConv代码实现

import torch
import torch.nn.functional as F
import torch.nn as nn
 
 
class GroupBatchnorm2d(nn.Module):
    def __init__(self, c_num: int,
                 group_num: int = 16,
                 eps: float = 1e-10
                 ):
        super(GroupBatchnorm2d, self).__init__()
        assert c_num >= group_num
        self.group_num = group_num
        self.weight = nn.Parameter(torch.randn(c_num, 1, 1))
        self.bias = nn.Parameter(torch.zeros(c_num, 1, 1))
        self.eps = eps
 
    def forward(self, x):
        N, C, H, W = x.size()
        x = x.view(N, self.group_num, -1)
        mean = x.mean(dim=2, keepdim=True)
        std = x.std(dim=2, keepdim=True)
        x = (x - mean) / (std + self.eps)
        x = x.view(N, C, H, W)
        return x * self.weight + self.bias
 
 
class SRU(nn.Module):
    def __init__(self,
                 oup_channels: int,
                 group_num: int = 16,
                 gate_treshold: float = 0.5,
                 torch_gn: bool = True
                 ):
        super().__init__()
 
        self.gn = nn.GroupNorm(num_channels=oup_channels, num_groups=group_num) if torch_gn else GroupBatchnorm2d(
            c_num=oup_channels, group_num=group_num)
        self.gate_treshold = gate_treshold
        self.sigomid = nn.Sigmoid()
 
    def forward(self, x):
        gn_x = self.gn(x)
        w_gamma = self.gn.weight / sum(self.gn.weight)
        w_gamma = w_gamma.view(1, -1, 1, 1)
        reweigts = self.sigomid(gn_x * w_gamma)
        # Gate
        w1 = torch.where(reweigts > self.gate_treshold, torch.ones_like(reweigts), reweigts)  # 大于门限值的设为1，否则保留原值
        w2 = torch.where(reweigts > self.gate_treshold, torch.zeros_like(reweigts), reweigts)  # 大于门限值的设为0，否则保留原值
        x_1 = w1 * x
        x_2 = w2 * x
        y = self.reconstruct(x_1, x_2)
        return y
 
    def reconstruct(self, x_1, x_2):
        x_11, x_12 = torch.split(x_1, x_1.size(1) // 2, dim=1)
        x_21, x_22 = torch.split(x_2, x_2.size(1) // 2, dim=1)
        return torch.cat([x_11 + x_22, x_12 + x_21], dim=1)
 
 
class CRU(nn.Module):
    '''
    alpha: 0<alpha<1
    '''
 
    def __init__(self,
                 op_channel: int,
                 alpha: float = 1 / 2,
                 squeeze_radio: int = 2,
                 group_size: int = 2,
                 group_kernel_size: int = 3,
                 ):
        super().__init__()
        self.up_channel = up_channel = int(alpha * op_channel)
        self.low_channel = low_channel = op_channel - up_channel
        self.squeeze1 = nn.Conv2d(up_channel, up_channel // squeeze_radio, kernel_size=1, bias=False)
        self.squeeze2 = nn.Conv2d(low_channel, low_channel // squeeze_radio, kernel_size=1, bias=False)
        # up
        self.GWC = nn.Conv2d(up_channel // squeeze_radio, op_channel, kernel_size=group_kernel_size, stride=1,
                             padding=group_kernel_size // 2, groups=group_size)
        self.PWC1 = nn.Conv2d(up_channel // squeeze_radio, op_channel, kernel_size=1, bias=False)
        # low
        self.PWC2 = nn.Conv2d(low_channel // squeeze_radio, op_channel - low_channel // squeeze_radio, kernel_size=1,
                              bias=False)
        self.advavg = nn.AdaptiveAvgPool2d(1)
 
    def forward(self, x):
        # Split
        up, low = torch.split(x, [self.up_channel, self.low_channel], dim=1)
        up, low = self.squeeze1(up), self.squeeze2(low)
        # Transform
        Y1 = self.GWC(up) + self.PWC1(up)
        Y2 = torch.cat([self.PWC2(low), low], dim=1)
        # Fuse
        out = torch.cat([Y1, Y2], dim=1)
        out = F.softmax(self.advavg(out), dim=1) * out
        out1, out2 = torch.split(out, out.size(1) // 2, dim=1)
        return out1 + out2
 
 
class ScConv(nn.Module):
    def __init__(self,
                 op_channel: int,
                 group_num: int = 4,
                 gate_treshold: float = 0.5,
                 alpha: float = 1 / 2,
                 squeeze_radio: int = 2,
                 group_size: int = 2,
                 group_kernel_size: int = 3,
                 ):
        super().__init__()
        self.SRU = SRU(op_channel,
                       group_num=group_num,
                       gate_treshold=gate_treshold)
        self.CRU = CRU(op_channel,
                       alpha=alpha,
                       squeeze_radio=squeeze_radio,
                       group_size=group_size,
                       group_kernel_size=group_kernel_size)
 
    def forward(self, x):
        x = self.SRU(x)
        x = self.CRU(x)
        return x
 
 
if __name__ == '__main__':
    x = torch.randn(1, 32, 16, 16)
    model = ScConv(32)
    print(model(x).shape)

SCConv嵌入时额外添加调用函数

YOLOv8中直接嵌入会报错而且参数对不上，所以需要额外定义一个函数作为中转

class SCConv_yolov8(nn.Module):
    def __init__(self, in_channels, out_channels, kernel_size=1, stride=1, g=1, dilation=1):
        super().__init__()
        self.conv = Conv(in_channels, out_channels, k=1)
 
        self.RFAConv = ScConv(out_channels)
 
        self.bn = nn.BatchNorm2d(out_channels)
 
        self.gelu = nn.GELU()
 
    def forward(self, x):
        x = self.conv(x)
 
        x = self.RFAConv(x)
 
        x = self.gelu(self.bn(x))
        return x

将SCConv嵌入C2f与Bottleneck模块

class Bottleneck_SCConv(nn.Module):
    """Standard bottleneck."""
 
    def __init__(self, c1, c2, shortcut=True, g=1, k=(3, 3), e=0.5):
        """Initializes a bottleneck module with given input/output channels, shortcut option, group, kernels, and
        expansion.
        """
        super().__init__()
        c_ = int(c2 * e)  # hidden channels
        self.cv1 = Conv(c1, c_, k[0], 1)
        self.cv2 = SCConv_yolov8(c_, c2, k[1], 1, g=g)
        self.add = shortcut and c1 == c2
 
    def forward(self, x):
        """'forward()' applies the YOLO FPN to input data."""
        return x + self.cv2(self.cv1(x)) if self.add else self.cv2(self.cv1(x))
 
 
class C2f_SCConv(nn.Module):
    """Faster Implementation of CSP Bottleneck with 2 convolutions."""
    def __init__(self, c1, c2, n=1, shortcut=False, g=1, e=0.5):
        """Initialize CSP bottleneck layer with two convolutions with arguments ch_in, ch_out, number, shortcut, groups,
        expansion.
        """
        super().__init__()
        self.c = int(c2 * e)  # hidden channels
        self.cv1 = Conv(c1, 2 * self.c, 1, 1)
        self.cv2 = Conv((2 + n) * self.c, c2, 1)  # optional act=FReLU(c2)
        self.m = nn.ModuleList(Bottleneck_SCConv(self.c, self.c, shortcut, g, k=((3, 3), (3, 3)), e=1.0) for _ in range(n))
 
    def forward(self, x):
        """Forward pass through C2f layer."""
        x = self.cv1(x)
        x = x.chunk(2, 1)
        y = list(x)
        # y = list(self.cv1(x).chunk(2, 1))
        y.extend(m(y[-1]) for m in self.m)
        return self.cv2(torch.cat(y, 1))
 
    def forward_split(self, x):
        """Forward pass using split() instead of chunk()."""
        y = list(self.cv1(x).split((self.c, self.c), 1))
        y.extend(m(y[-1]) for m in self.m)
        return self.cv2(torch.cat(y, 1))

参考案例

# Ultralytics YOLO 🚀, AGPL-3.0 license
# YOLOv8 object detection model with P3-P5 outputs. For Usage examples see https://docs.ultralytics.com/tasks/detect
 
# Parameters
nc: 80  # number of classes
scales: # model compound scaling constants, i.e. 'model=yolov8n.yaml' will call yolov8.yaml with scale 'n'
  # [depth, width, max_channels]
  n: [0.33, 0.25, 1024]  # YOLOv8n summary: 225 layers,  3157200 parameters,  3157184 gradients,   8.9 GFLOPs
  s: [0.33, 0.50, 1024]  # YOLOv8s summary: 225 layers, 11166560 parameters, 11166544 gradients,  28.8 GFLOPs
  m: [0.67, 0.75, 768]   # YOLOv8m summary: 295 layers, 25902640 parameters, 25902624 gradients,  79.3 GFLOPs
  l: [1.00, 1.00, 512]   # YOLOv8l summary: 365 layers, 43691520 parameters, 43691504 gradients, 165.7 GFLOPs
  x: [1.00, 1.25, 512]   # YOLOv8x summary: 365 layers, 68229648 parameters, 68229632 gradients, 258.5 GFLOPs
 
# YOLOv8.0n 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, 3, C2f, [128, True]]
  - [-1, 1, Conv, [256, 3, 2]]  # 3-P3/8
  - [-1, 6, C2f, [256, True]]
  - [-1, 1, Conv, [512, 3, 2]]  # 5-P4/16
  - [-1, 6, C2f, [512, True]]
  - [-1, 1, Conv, [1024, 3, 2]]  # 7-P5/32
  - [-1, 3, C2f, [1024, True]]
  - [-1, 1, SPPF, [1024, 5]]  # 9
 
 
# YOLOv8.0n head
head:
  - [-1, 1, nn.Upsample, [None, 2, 'nearest']]
  - [[-1, 6], 1, Concat, [1]]  # cat backbone P4
  - [-1, 3, C2f, [512]]  # 12
 
  - [-1, 1, nn.Upsample, [None, 2, 'nearest']]
  - [[-1, 4], 1, Concat, [1]]  # cat backbone P3
  - [-1, 3, C2f_SCConv, [256]]  # 15 (P3/8-small)
 
  - [-1, 1, Conv, [256, 3, 2]]
  - [[-1, 12], 1, Concat, [1]]  # cat head P4
  - [-1, 3, C2f_SCConv, [512]]  # 18 (P4/16-medium)
 
  - [-1, 1, Conv, [512, 3, 2]]
  - [[-1, 9], 1, Concat, [1]]  # cat head P5
  - [-1, 3, C2f_SCConv, [1024]]  # 21 (P5/32-large)
 
  - [[15, 18, 21], 1, Detect, [nc]]  # Detect(P3, P4, P5)