【YOLOv5/v7改進系列】改進池化層為RFB

一、導言

論文 "Receptive Field Block Net for Accurate and Fast Object Detection" 中提出的 RFB (Receptive Field Block) 模塊旨在模仿人類視覺系統中的感受野結構，以增強深度學習模型對不同尺度和位置的目標檢測能力。下面總結了RFB模塊的主要優點和潛在局限性。

優點:

增強特征區分性和魯棒性: RFB模塊通過模擬人類視覺系統中感受野的大小和偏心率之間的關系，增強了輕量級CNN網絡的特征表示，從而提高了特征的區分性和魯棒性。
多尺度信息整合: RFB模塊利用多個分支，每個分支有不同的卷積核大小和空洞卷積層，這有助于捕捉圖像中不同尺度的信息，類似于人類視覺系統中感受野的多樣性。
實時性能: 實驗表明，將RFB模塊添加到SSD之上構建的RFB Net不僅保持了實時處理速度，而且在Pascal VOC和MS COCO數據集上達到了與高級深層檢測器相當的性能。
通用性: RFB模塊可以很容易地鏈接到不同的輕量級網絡架構上，如MobileNet，這證明了它的通用性和適應性。
從零開始訓練的能力: RFB模塊還顯示出即使在沒有預訓練的情況下也能有效訓練物體檢測器的能力，這在某些情況下可能是一個優勢。

局限性:

參數增加: 盡管RFB模塊可以提高精度，但它也增加了額外的層和參數，這可能會影響計算效率和資源需求，尤其是在低端設備上。
特定設計的局限性: RFB模塊的設計是手工制作的，這意味著它可能不如自適應機制靈活，例如可變形卷積神經網絡中使用的那些，后者可以根據對象的尺度和形狀調整感受野的分布。
對感受野的簡化假設: RFB模塊通過固定大小和偏心率的感受野來近似人類視覺系統，這可能忽略了更復雜的人類視覺處理機制，如動態調整或非均勻采樣。
依賴于基礎網絡: RFB模塊的性能很大程度上依賴于底層的基礎網絡，這意味著在不同的網絡架構上的效果可能會有所不同。

盡管存在這些局限性，RFB模塊在物體檢測任務中表現出了顯著的改進，并且在保持實時處理速度的同時，提供了一種增強輕量級模型檢測精度的有效方法。

二、準備工作

首先在YOLOv5/v7的models文件夾下新建文件morepooling.py，導入如下代碼

from models.common import *# RFB
# https://arxiv.org/pdf/1711.07767
class BasicConv(nn.Module):def __init__(self, in_planes, out_planes, kernel_size, stride=1, padding=0, dilation=1, groups=1, relu=True,bn=True):super(BasicConv, self).__init__()self.out_channels = out_planesif bn:self.conv = nn.Conv2d(in_planes, out_planes, kernel_size=kernel_size, stride=stride, padding=padding,dilation=dilation, groups=groups, bias=False)self.bn = nn.BatchNorm2d(out_planes, eps=1e-5, momentum=0.01, affine=True)self.relu = nn.ReLU(inplace=True) if relu else Noneelse:self.conv = nn.Conv2d(in_planes, out_planes, kernel_size=kernel_size, stride=stride, padding=padding,dilation=dilation, groups=groups, bias=True)self.bn = Noneself.relu = nn.ReLU(inplace=True) if relu else Nonedef forward(self, x):x = self.conv(x)if self.bn is not None:x = self.bn(x)if self.relu is not None:x = self.relu(x)return xclass BasicRFB(nn.Module):def __init__(self, in_planes, out_planes, stride=1, scale=0.1, map_reduce=8, vision=1, groups=1):super(BasicRFB, self).__init__()self.scale = scaleself.out_channels = out_planesinter_planes = in_planes // map_reduceself.branch0 = nn.Sequential(BasicConv(in_planes, inter_planes, kernel_size=1, stride=1, groups=groups, relu=False),BasicConv(inter_planes, 2 * inter_planes, kernel_size=(3, 3), stride=stride, padding=(1, 1), groups=groups),BasicConv(2 * inter_planes, 2 * inter_planes, kernel_size=3, stride=1, padding=vision, dilation=vision,relu=False, groups=groups))self.branch1 = nn.Sequential(BasicConv(in_planes, inter_planes, kernel_size=1, stride=1, groups=groups, relu=False),BasicConv(inter_planes, 2 * inter_planes, kernel_size=(3, 3), stride=stride, padding=(1, 1), groups=groups),BasicConv(2 * inter_planes, 2 * inter_planes, kernel_size=3, stride=1, padding=vision + 2,dilation=vision + 2, relu=False, groups=groups))self.branch2 = nn.Sequential(BasicConv(in_planes, inter_planes, kernel_size=1, stride=1, groups=groups, relu=False),BasicConv(inter_planes, (inter_planes // 2) * 3, kernel_size=3, stride=1, padding=1, groups=groups),BasicConv((inter_planes // 2) * 3, 2 * inter_planes, kernel_size=3, stride=stride, padding=1,groups=groups),BasicConv(2 * inter_planes, 2 * inter_planes, kernel_size=3, stride=1, padding=vision + 4,dilation=vision + 4, relu=False, groups=groups))self.ConvLinear = BasicConv(6 * inter_planes, out_planes, kernel_size=1, stride=1, relu=False)self.shortcut = BasicConv(in_planes, out_planes, kernel_size=1, stride=stride, relu=False)self.relu = nn.ReLU(inplace=False)def forward(self, x):x0 = self.branch0(x)x1 = self.branch1(x)x2 = self.branch2(x)out = torch.cat((x0, x1, x2), 1)out = self.ConvLinear(out)short = self.shortcut(x)out = out * self.scale + shortout = self.relu(out)return out

其次在在YOLOv5/v7項目文件下的models/yolo.py中在文件首部添加代碼

from models.morepooling import *

并搜索def parse_model(d, ch)

定位到如下行添加以下代碼

BasicRFB

三、YOLOv7-tiny改進工作

完成二后，在YOLOv7項目文件下的models文件夾下創建新的文件yolov7-tiny-rfb.yaml，導入如下代碼。

# parameters
nc: 80  # number of classes
depth_multiple: 1.0  # model depth multiple
width_multiple: 1.0  # layer channel multiple# anchors
anchors:- [10,13, 16,30, 33,23]  # P3/8- [30,61, 62,45, 59,119]  # P4/16- [116,90, 156,198, 373,326]  # P5/32# yolov7-tiny backbone
backbone:# [from, number, module, args] c2, k=1, s=1, p=None, g=1, act=True[[-1, 1, Conv, [32, 3, 2, None, 1, nn.LeakyReLU(0.1)]],  # 0-P1/2[-1, 1, Conv, [64, 3, 2, None, 1, nn.LeakyReLU(0.1)]],  # 1-P2/4[-1, 1, Conv, [32, 1, 1, None, 1, nn.LeakyReLU(0.1)]],[-2, 1, Conv, [32, 1, 1, None, 1, nn.LeakyReLU(0.1)]],[-1, 1, Conv, [32, 3, 1, None, 1, nn.LeakyReLU(0.1)]],[-1, 1, Conv, [32, 3, 1, None, 1, nn.LeakyReLU(0.1)]],[[-1, -2, -3, -4], 1, Concat, [1]],[-1, 1, Conv, [64, 1, 1, None, 1, nn.LeakyReLU(0.1)]],  # 7[-1, 1, MP, []],  # 8-P3/8[-1, 1, Conv, [64, 1, 1, None, 1, nn.LeakyReLU(0.1)]],[-2, 1, Conv, [64, 1, 1, None, 1, nn.LeakyReLU(0.1)]],[-1, 1, Conv, [64, 3, 1, None, 1, nn.LeakyReLU(0.1)]],[-1, 1, Conv, [64, 3, 1, None, 1, nn.LeakyReLU(0.1)]],[[-1, -2, -3, -4], 1, Concat, [1]],[-1, 1, Conv, [128, 1, 1, None, 1, nn.LeakyReLU(0.1)]],  # 14[-1, 1, MP, []],  # 15-P4/16[-1, 1, Conv, [128, 1, 1, None, 1, nn.LeakyReLU(0.1)]],[-2, 1, Conv, [128, 1, 1, None, 1, nn.LeakyReLU(0.1)]],[-1, 1, Conv, [128, 3, 1, None, 1, nn.LeakyReLU(0.1)]],[-1, 1, Conv, [128, 3, 1, None, 1, nn.LeakyReLU(0.1)]],[[-1, -2, -3, -4], 1, Concat, [1]],[-1, 1, Conv, [256, 1, 1, None, 1, nn.LeakyReLU(0.1)]],  # 21[-1, 1, MP, []],  # 22-P5/32[-1, 1, Conv, [256, 1, 1, None, 1, nn.LeakyReLU(0.1)]],[-2, 1, Conv, [256, 1, 1, None, 1, nn.LeakyReLU(0.1)]],[-1, 1, Conv, [256, 3, 1, None, 1, nn.LeakyReLU(0.1)]],[-1, 1, Conv, [256, 3, 1, None, 1, nn.LeakyReLU(0.1)]],[[-1, -2, -3, -4], 1, Concat, [1]],[-1, 1, Conv, [512, 1, 1, None, 1, nn.LeakyReLU(0.1)]],  # 28]# yolov7-tiny head
head:[[-1, 1, BasicRFB, [256]], # 29[-1, 1, Conv, [128, 1, 1, None, 1, nn.LeakyReLU(0.1)]],[-1, 1, nn.Upsample, [None, 2, 'nearest']],[21, 1, Conv, [128, 1, 1, None, 1, nn.LeakyReLU(0.1)]], # route backbone P4[[-1, -2], 1, Concat, [1]],[-1, 1, Conv, [64, 1, 1, None, 1, nn.LeakyReLU(0.1)]],[-2, 1, Conv, [64, 1, 1, None, 1, nn.LeakyReLU(0.1)]],[-1, 1, Conv, [64, 3, 1, None, 1, nn.LeakyReLU(0.1)]],[-1, 1, Conv, [64, 3, 1, None, 1, nn.LeakyReLU(0.1)]],[[-1, -2, -3, -4], 1, Concat, [1]],[-1, 1, Conv, [128, 1, 1, None, 1, nn.LeakyReLU(0.1)]],  # 39[-1, 1, Conv, [64, 1, 1, None, 1, nn.LeakyReLU(0.1)]],[-1, 1, nn.Upsample, [None, 2, 'nearest']],[14, 1, Conv, [64, 1, 1, None, 1, nn.LeakyReLU(0.1)]], # route backbone P3[[-1, -2], 1, Concat, [1]],[-1, 1, Conv, [32, 1, 1, None, 1, nn.LeakyReLU(0.1)]],[-2, 1, Conv, [32, 1, 1, None, 1, nn.LeakyReLU(0.1)]],[-1, 1, Conv, [32, 3, 1, None, 1, nn.LeakyReLU(0.1)]],[-1, 1, Conv, [32, 3, 1, None, 1, nn.LeakyReLU(0.1)]],[[-1, -2, -3, -4], 1, Concat, [1]],[-1, 1, Conv, [64, 1, 1, None, 1, nn.LeakyReLU(0.1)]],  # 49[-1, 1, Conv, [128, 3, 2, None, 1, nn.LeakyReLU(0.1)]],[[-1, 39], 1, Concat, [1]],[-1, 1, Conv, [64, 1, 1, None, 1, nn.LeakyReLU(0.1)]],[-2, 1, Conv, [64, 1, 1, None, 1, nn.LeakyReLU(0.1)]],[-1, 1, Conv, [64, 3, 1, None, 1, nn.LeakyReLU(0.1)]],[-1, 1, Conv, [64, 3, 1, None, 1, nn.LeakyReLU(0.1)]],[[-1, -2, -3, -4], 1, Concat, [1]],[-1, 1, Conv, [128, 1, 1, None, 1, nn.LeakyReLU(0.1)]],  # 57[-1, 1, Conv, [256, 3, 2, None, 1, nn.LeakyReLU(0.1)]],[[-1, 29], 1, Concat, [1]],[-1, 1, Conv, [128, 1, 1, None, 1, nn.LeakyReLU(0.1)]],[-2, 1, Conv, [128, 1, 1, None, 1, nn.LeakyReLU(0.1)]],[-1, 1, Conv, [128, 3, 1, None, 1, nn.LeakyReLU(0.1)]],[-1, 1, Conv, [128, 3, 1, None, 1, nn.LeakyReLU(0.1)]],[[-1, -2, -3, -4], 1, Concat, [1]],[-1, 1, Conv, [256, 1, 1, None, 1, nn.LeakyReLU(0.1)]],  # 65[49, 1, Conv, [128, 3, 1, None, 1, nn.LeakyReLU(0.1)]],[57, 1, Conv, [256, 3, 1, None, 1, nn.LeakyReLU(0.1)]],[65, 1, Conv, [512, 3, 1, None, 1, nn.LeakyReLU(0.1)]],[[66, 67, 68], 1, IDetect, [nc, anchors]],   # Detect(P3, P4, P5)]

from  n    params  module                                  arguments                     0                -1  1       928  models.common.Conv                      [3, 32, 3, 2, None, 1, LeakyReLU(negative_slope=0.1)]1                -1  1     18560  models.common.Conv                      [32, 64, 3, 2, None, 1, LeakyReLU(negative_slope=0.1)]2                -1  1      2112  models.common.Conv                      [64, 32, 1, 1, None, 1, LeakyReLU(negative_slope=0.1)]3                -2  1      2112  models.common.Conv                      [64, 32, 1, 1, None, 1, LeakyReLU(negative_slope=0.1)]4                -1  1      9280  models.common.Conv                      [32, 32, 3, 1, None, 1, LeakyReLU(negative_slope=0.1)]5                -1  1      9280  models.common.Conv                      [32, 32, 3, 1, None, 1, LeakyReLU(negative_slope=0.1)]6  [-1, -2, -3, -4]  1         0  models.common.Concat                    [1]                           7                -1  1      8320  models.common.Conv                      [128, 64, 1, 1, None, 1, LeakyReLU(negative_slope=0.1)]8                -1  1         0  models.common.MP                        []                            9                -1  1      4224  models.common.Conv                      [64, 64, 1, 1, None, 1, LeakyReLU(negative_slope=0.1)]10                -2  1      4224  models.common.Conv                      [64, 64, 1, 1, None, 1, LeakyReLU(negative_slope=0.1)]11                -1  1     36992  models.common.Conv                      [64, 64, 3, 1, None, 1, LeakyReLU(negative_slope=0.1)]12                -1  1     36992  models.common.Conv                      [64, 64, 3, 1, None, 1, LeakyReLU(negative_slope=0.1)]13  [-1, -2, -3, -4]  1         0  models.common.Concat                    [1]                           14                -1  1     33024  models.common.Conv                      [256, 128, 1, 1, None, 1, LeakyReLU(negative_slope=0.1)]15                -1  1         0  models.common.MP                        []                            16                -1  1     16640  models.common.Conv                      [128, 128, 1, 1, None, 1, LeakyReLU(negative_slope=0.1)]17                -2  1     16640  models.common.Conv                      [128, 128, 1, 1, None, 1, LeakyReLU(negative_slope=0.1)]18                -1  1    147712  models.common.Conv                      [128, 128, 3, 1, None, 1, LeakyReLU(negative_slope=0.1)]19                -1  1    147712  models.common.Conv                      [128, 128, 3, 1, None, 1, LeakyReLU(negative_slope=0.1)]20  [-1, -2, -3, -4]  1         0  models.common.Concat                    [1]                           21                -1  1    131584  models.common.Conv                      [512, 256, 1, 1, None, 1, LeakyReLU(negative_slope=0.1)]22                -1  1         0  models.common.MP                        []                            23                -1  1     66048  models.common.Conv                      [256, 256, 1, 1, None, 1, LeakyReLU(negative_slope=0.1)]24                -2  1     66048  models.common.Conv                      [256, 256, 1, 1, None, 1, LeakyReLU(negative_slope=0.1)]25                -1  1    590336  models.common.Conv                      [256, 256, 3, 1, None, 1, LeakyReLU(negative_slope=0.1)]26                -1  1    590336  models.common.Conv                      [256, 256, 3, 1, None, 1, LeakyReLU(negative_slope=0.1)]27  [-1, -2, -3, -4]  1         0  models.common.Concat                    [1]                           28                -1  1    525312  models.common.Conv                      [1024, 512, 1, 1, None, 1, LeakyReLU(negative_slope=0.1)]29                -1  1   1086528  models.morepooling.BasicRFB             [512, 256]                    30                -1  1     33024  models.common.Conv                      [256, 128, 1, 1, None, 1, LeakyReLU(negative_slope=0.1)]31                -1  1         0  torch.nn.modules.upsampling.Upsample    [None, 2, 'nearest']          32                21  1     33024  models.common.Conv                      [256, 128, 1, 1, None, 1, LeakyReLU(negative_slope=0.1)]33          [-1, -2]  1         0  models.common.Concat                    [1]                           34                -1  1     16512  models.common.Conv                      [256, 64, 1, 1, None, 1, LeakyReLU(negative_slope=0.1)]35                -2  1     16512  models.common.Conv                      [256, 64, 1, 1, None, 1, LeakyReLU(negative_slope=0.1)]36                -1  1     36992  models.common.Conv                      [64, 64, 3, 1, None, 1, LeakyReLU(negative_slope=0.1)]37                -1  1     36992  models.common.Conv                      [64, 64, 3, 1, None, 1, LeakyReLU(negative_slope=0.1)]38  [-1, -2, -3, -4]  1         0  models.common.Concat                    [1]                           39                -1  1     33024  models.common.Conv                      [256, 128, 1, 1, None, 1, LeakyReLU(negative_slope=0.1)]40                -1  1      8320  models.common.Conv                      [128, 64, 1, 1, None, 1, LeakyReLU(negative_slope=0.1)]41                -1  1         0  torch.nn.modules.upsampling.Upsample    [None, 2, 'nearest']          42                14  1      8320  models.common.Conv                      [128, 64, 1, 1, None, 1, LeakyReLU(negative_slope=0.1)]43          [-1, -2]  1         0  models.common.Concat                    [1]                           44                -1  1      4160  models.common.Conv                      [128, 32, 1, 1, None, 1, LeakyReLU(negative_slope=0.1)]45                -2  1      4160  models.common.Conv                      [128, 32, 1, 1, None, 1, LeakyReLU(negative_slope=0.1)]46                -1  1      9280  models.common.Conv                      [32, 32, 3, 1, None, 1, LeakyReLU(negative_slope=0.1)]47                -1  1      9280  models.common.Conv                      [32, 32, 3, 1, None, 1, LeakyReLU(negative_slope=0.1)]48  [-1, -2, -3, -4]  1         0  models.common.Concat                    [1]                           49                -1  1      8320  models.common.Conv                      [128, 64, 1, 1, None, 1, LeakyReLU(negative_slope=0.1)]50                -1  1     73984  models.common.Conv                      [64, 128, 3, 2, None, 1, LeakyReLU(negative_slope=0.1)]51          [-1, 39]  1         0  models.common.Concat                    [1]                           52                -1  1     16512  models.common.Conv                      [256, 64, 1, 1, None, 1, LeakyReLU(negative_slope=0.1)]53                -2  1     16512  models.common.Conv                      [256, 64, 1, 1, None, 1, LeakyReLU(negative_slope=0.1)]54                -1  1     36992  models.common.Conv                      [64, 64, 3, 1, None, 1, LeakyReLU(negative_slope=0.1)]55                -1  1     36992  models.common.Conv                      [64, 64, 3, 1, None, 1, LeakyReLU(negative_slope=0.1)]56  [-1, -2, -3, -4]  1         0  models.common.Concat                    [1]                           57                -1  1     33024  models.common.Conv                      [256, 128, 1, 1, None, 1, LeakyReLU(negative_slope=0.1)]58                -1  1    295424  models.common.Conv                      [128, 256, 3, 2, None, 1, LeakyReLU(negative_slope=0.1)]59          [-1, 29]  1         0  models.common.Concat                    [1]                           60                -1  1     65792  models.common.Conv                      [512, 128, 1, 1, None, 1, LeakyReLU(negative_slope=0.1)]61                -2  1     65792  models.common.Conv                      [512, 128, 1, 1, None, 1, LeakyReLU(negative_slope=0.1)]62                -1  1    147712  models.common.Conv                      [128, 128, 3, 1, None, 1, LeakyReLU(negative_slope=0.1)]63                -1  1    147712  models.common.Conv                      [128, 128, 3, 1, None, 1, LeakyReLU(negative_slope=0.1)]64  [-1, -2, -3, -4]  1         0  models.common.Concat                    [1]                           65                -1  1    131584  models.common.Conv                      [512, 256, 1, 1, None, 1, LeakyReLU(negative_slope=0.1)]66                49  1     73984  models.common.Conv                      [64, 128, 3, 1, None, 1, LeakyReLU(negative_slope=0.1)]67                57  1    295424  models.common.Conv                      [128, 256, 3, 1, None, 1, LeakyReLU(negative_slope=0.1)]68                65  1   1180672  models.common.Conv                      [256, 512, 3, 1, None, 1, LeakyReLU(negative_slope=0.1)]69      [66, 67, 68]  1     17132  models.yolo.IDetect                     [1, [[10, 13, 16, 30, 33, 23], [30, 61, 62, 45, 59, 119], [116, 90, 156, 198, 373, 326]], [128, 256, 512]]Model Summary: 284 layers, 6444108 parameters, 6444108 gradients, 13.5 GFLOPS

運行后若打印出如上文本代表改進成功。

四、YOLOv5s改進工作

完成二后，在YOLOv5項目文件下的models文件夾下創建新的文件yolov5s-rfb.yaml，導入如下代碼。

# Parameters
nc: 1  # number of classes
depth_multiple: 0.33  # model depth multiple
width_multiple: 0.50  # layer channel multiple
anchors:- [10,13, 16,30, 33,23]  # P3/8- [30,61, 62,45, 59,119]  # P4/16- [116,90, 156,198, 373,326]  # P5/32# YOLOv5 v6.0 backbone
backbone:# [from, number, module, args][[-1, 1, Conv, [64, 6, 2, 2]],  # 0-P1/2[-1, 1, Conv, [128, 3, 2]],  # 1-P2/4[-1, 3, C3, [128]],[-1, 1, Conv, [256, 3, 2]],  # 3-P3/8[-1, 6, C3, [256]],[-1, 1, Conv, [512, 3, 2]],  # 5-P4/16[-1, 9, C3, [512]],[-1, 1, Conv, [1024, 3, 2]],  # 7-P5/32[-1, 3, C3, [1024]],#[-1, 1, ASPP, [1024]],  # 9[-1, 1, BasicRFB, [1024]],#[-1, 1, SPP, [1024]],#[-1, 1, SPPF, [1024, 5]],  # 9#[-1, 1, SPPCSPC, [1024]],]# YOLOv5 v6.0 head
head:[[-1, 1, Conv, [512, 1, 1]],[-1, 1, nn.Upsample, [None, 2, 'nearest']],[[-1, 6], 1, Concat, [1]],  # cat backbone P4[-1, 3, C3, [512, False]],  # 13[-1, 1, Conv, [256, 1, 1]],[-1, 1, nn.Upsample, [None, 2, 'nearest']],[[-1, 4], 1, Concat, [1]],  # cat backbone P3[-1, 3, C3, [256, False]],  # 17 (P3/8-small)[-1, 1, Conv, [256, 3, 2]],[[-1, 14], 1, Concat, [1]],  # cat head P4[-1, 3, C3, [512, False]],  # 20 (P4/16-medium)[-1, 1, Conv, [512, 3, 2]],[[-1, 10], 1, Concat, [1]],  # cat head P5[-1, 3, C3, [1024, False]],  # 23 (P5/32-large)[[17, 20, 23], 1, Detect, [nc, anchors]],  # Detect(P3, P4, P5)]

from  n    params  module                                  arguments                     0                -1  1      3520  models.common.Conv                      [3, 32, 6, 2, 2]              1                -1  1     18560  models.common.Conv                      [32, 64, 3, 2]                2                -1  1     18816  models.common.C3                        [64, 64, 1]                   3                -1  1     73984  models.common.Conv                      [64, 128, 3, 2]               4                -1  2    115712  models.common.C3                        [128, 128, 2]                 5                -1  1    295424  models.common.Conv                      [128, 256, 3, 2]              6                -1  3    625152  models.common.C3                        [256, 256, 3]                 7                -1  1   1180672  models.common.Conv                      [256, 512, 3, 2]              8                -1  1   1182720  models.common.C3                        [512, 512, 1]                 9                -1  1   1316928  models.morepooling.BasicRFB             [512, 512]                    10                -1  1    131584  models.common.Conv                      [512, 256, 1, 1]              11                -1  1         0  torch.nn.modules.upsampling.Upsample    [None, 2, 'nearest']          12           [-1, 6]  1         0  models.common.Concat                    [1]                           13                -1  1    361984  models.common.C3                        [512, 256, 1, False]          14                -1  1     33024  models.common.Conv                      [256, 128, 1, 1]              15                -1  1         0  torch.nn.modules.upsampling.Upsample    [None, 2, 'nearest']          16           [-1, 4]  1         0  models.common.Concat                    [1]                           17                -1  1     90880  models.common.C3                        [256, 128, 1, False]          18                -1  1    147712  models.common.Conv                      [128, 128, 3, 2]              19          [-1, 14]  1         0  models.common.Concat                    [1]                           20                -1  1    296448  models.common.C3                        [256, 256, 1, False]          21                -1  1    590336  models.common.Conv                      [256, 256, 3, 2]              22          [-1, 10]  1         0  models.common.Concat                    [1]                           23                -1  1   1182720  models.common.C3                        [512, 512, 1, False]          24      [17, 20, 23]  1     16182  models.yolo.Detect                      [1, [[10, 13, 16, 30, 33, 23], [30, 61, 62, 45, 59, 119], [116, 90, 156, 198, 373, 326]], [128, 256, 512]]Model Summary: 305 layers, 7682358 parameters, 7682358 gradients, 16.5 GFLOPs

運行后若打印出如上文本代表改進成功。

五、YOLOv5n改進工作

完成二后，在YOLOv5項目文件下的models文件夾下創建新的文件yolov5n-rfb.yaml，導入如下代碼。

# Parameters
nc: 1  # number of classes
depth_multiple: 0.33  # model depth multiple
width_multiple: 0.25  # layer channel multiple
anchors:- [10,13, 16,30, 33,23]  # P3/8- [30,61, 62,45, 59,119]  # P4/16- [116,90, 156,198, 373,326]  # P5/32# YOLOv5 v6.0 backbone
backbone:# [from, number, module, args][[-1, 1, Conv, [64, 6, 2, 2]],  # 0-P1/2[-1, 1, Conv, [128, 3, 2]],  # 1-P2/4[-1, 3, C3, [128]],[-1, 1, Conv, [256, 3, 2]],  # 3-P3/8[-1, 6, C3, [256]],[-1, 1, Conv, [512, 3, 2]],  # 5-P4/16[-1, 9, C3, [512]],[-1, 1, Conv, [1024, 3, 2]],  # 7-P5/32[-1, 3, C3, [1024]],#[-1, 1, ASPP, [1024]],  # 9[-1, 1, BasicRFB, [1024]],#[-1, 1, SPP, [1024]],#[-1, 1, SPPF, [1024, 5]],  # 9#[-1, 1, SPPCSPC, [1024]],]# YOLOv5 v6.0 head
head:[[-1, 1, Conv, [512, 1, 1]],[-1, 1, nn.Upsample, [None, 2, 'nearest']],[[-1, 6], 1, Concat, [1]],  # cat backbone P4[-1, 3, C3, [512, False]],  # 13[-1, 1, Conv, [256, 1, 1]],[-1, 1, nn.Upsample, [None, 2, 'nearest']],[[-1, 4], 1, Concat, [1]],  # cat backbone P3[-1, 3, C3, [256, False]],  # 17 (P3/8-small)[-1, 1, Conv, [256, 3, 2]],[[-1, 14], 1, Concat, [1]],  # cat head P4[-1, 3, C3, [512, False]],  # 20 (P4/16-medium)[-1, 1, Conv, [512, 3, 2]],[[-1, 10], 1, Concat, [1]],  # cat head P5[-1, 3, C3, [1024, False]],  # 23 (P5/32-large)[[17, 20, 23], 1, Detect, [nc, anchors]],  # Detect(P3, P4, P5)]

from  n    params  module                                  arguments                     0                -1  1      1760  models.common.Conv                      [3, 16, 6, 2, 2]              1                -1  1      4672  models.common.Conv                      [16, 32, 3, 2]                2                -1  1      4800  models.common.C3                        [32, 32, 1]                   3                -1  1     18560  models.common.Conv                      [32, 64, 3, 2]                4                -1  2     29184  models.common.C3                        [64, 64, 2]                   5                -1  1     73984  models.common.Conv                      [64, 128, 3, 2]               6                -1  3    156928  models.common.C3                        [128, 128, 3]                 7                -1  1    295424  models.common.Conv                      [128, 256, 3, 2]              8                -1  1    296448  models.common.C3                        [256, 256, 1]                 9                -1  1    330272  models.morepooling.BasicRFB             [256, 256]                    10                -1  1     33024  models.common.Conv                      [256, 128, 1, 1]              11                -1  1         0  torch.nn.modules.upsampling.Upsample    [None, 2, 'nearest']          12           [-1, 6]  1         0  models.common.Concat                    [1]                           13                -1  1     90880  models.common.C3                        [256, 128, 1, False]          14                -1  1      8320  models.common.Conv                      [128, 64, 1, 1]               15                -1  1         0  torch.nn.modules.upsampling.Upsample    [None, 2, 'nearest']          16           [-1, 4]  1         0  models.common.Concat                    [1]                           17                -1  1     22912  models.common.C3                        [128, 64, 1, False]           18                -1  1     36992  models.common.Conv                      [64, 64, 3, 2]                19          [-1, 14]  1         0  models.common.Concat                    [1]                           20                -1  1     74496  models.common.C3                        [128, 128, 1, False]          21                -1  1    147712  models.common.Conv                      [128, 128, 3, 2]              22          [-1, 10]  1         0  models.common.Concat                    [1]                           23                -1  1    296448  models.common.C3                        [256, 256, 1, False]          24      [17, 20, 23]  1      8118  models.yolo.Detect                      [1, [[10, 13, 16, 30, 33, 23], [30, 61, 62, 45, 59, 119], [116, 90, 156, 198, 373, 326]], [64, 128, 256]]Model Summary: 305 layers, 1930934 parameters, 1930934 gradients, 4.4 GFLOPs

六、代碼部分的解釋

BasicRFB 類繼承自 PyTorch 的 nn.Module。構造函數接收輸入通道數 in_planes、輸出通道數 out_planes 和一些控制模塊行為的參數，比如步長 stride、縮放因子 scale、中間層通道減少倍數 map_reduce、擴張率 vision 和分組卷積的組數 groups。

三個分支分別定義為 branch0、branch1 和 branch2。每個分支都由多個 BasicConv 組件構成，其中包含卷積、批量歸一化和激活函數。分支的內核大小、填充和擴張率各不相同，目的是捕捉不同尺度的信息。branch0 使用標準卷積和擴張卷積；branch1 使用稍大的擴張率；而 branch2 則使用更大的擴張率和額外的卷積層，進一步增加感受野的多樣性。

最終，三個分支的輸出被拼接在一起，并通過 ConvLinear 卷積層轉換為期望的輸出通道數。此外，還有一個快捷連接（shortcut）從輸入直接傳遞到輸出，與 ResNet 結構類似，用于緩解梯度消失問題。所有分支的輸出和快捷連接的輸出在相加前會乘以一個縮放因子 scale，然后經過 ReLU 激活函數，得到最終的輸出。

整個 BasicRFB 模塊在前向傳播時，將輸入通過三個分支并行處理，然后將結果拼接后進行線性變換，最后加上快捷連接的輸出。這種設計使得模塊能夠高效地捕獲多尺度特征，同時保持實時處理速度，適用于目標檢測等計算機視覺任務。

運行后打印如上代碼說明改進成功。

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