详细解释 if use_large_stem: self.stem = nn.Sequential( ('conv1', ConvBNLayer( 3, channels[0] // 2, 3, stride=2, padding=1, act=act)), ('conv2', ConvBNLayer( channels[0] // 2, channels[0] // 2, 3, stride=1, padding=1, act=act)), ('conv3', ConvBNLayer( channels[0] // 2, channels[0], 3, stride=1, padding=1, act=act))) else: self.stem = nn.Sequential( ('conv1', ConvBNLayer( 3, channels[0] // 2, 3, stride=2, padding=1, act=act)), ('conv2', ConvBNLayer( channels[0] // 2, channels[0], 3, stride=1, padding=1, act=act)))
时间: 2023-06-16 16:02:04 浏览: 71
这段代码是一个神经网络模型中的前置处理部分,即输入预处理部分,通常也被称为模型的“骨架”。它根据输入图片的大小(通常是3x224x224)将输入数据进行一系列的卷积操作,将其转换为较高层次的特征表示。其中,卷积操作被封装在 `ConvBNLayer` 函数中,用于进行卷积层和批归一化层的计算。
这段代码中,通过 `if-else` 语句来判断是否使用 `large` 模式。如果使用 `large` 模式,会在 `self.stem` 中添加一个额外的卷积层 `conv3`,否则只添加两个卷积层 `conv1` 和 `conv2`。具体来说:
- 第一层卷积层 `conv1` 将输入图片从3个通道转换为 `channels[0] // 2` 个特征通道,同时进行一次下采样(stride=2),其目的是为了缩小特征图的尺寸。
- 第二层卷积层 `conv2` 将特征通道数从 `channels[0] // 2` 扩展到 `channels[0]`,同时保持特征图尺寸不变。
- 如果使用 `large` 模式,还会添加第三层卷积层 `conv3`,将特征通道数从 `channels[0] // 2` 扩展到 `channels[0]`,同时保持特征图尺寸不变。
这样,经过输入预处理后,得到的特征图就可以作为后续卷积层的输入,不断进行卷积和池化操作,从而逐渐提取出更高层次的特征信息,最终得到对输入图片的分类结果。
相关问题
class HorNet(nn.Module): # HorNet # hornet by iscyy/yoloair def __init__(self, index, in_chans, depths, dim_base, drop_path_rate=0.,layer_scale_init_value=1e-6, gnconv=[ partial(gnconv, order=2, s=1.0/3.0), partial(gnconv, order=3, s=1.0/3.0), partial(gnconv, order=4, s=1.0/3.0), partial(gnconv, order=5, s=1.0/3.0), # GlobalLocalFilter ], ): super().__init__() dims = [dim_base, dim_base * 2, dim_base * 4, dim_base * 8] self.index = index self.downsample_layers = nn.ModuleList() # stem and 3 intermediate downsampling conv layers hornet by iscyy/air stem = nn.Sequential( nn.Conv2d(in_chans, dims[0], kernel_size=4, stride=4), HorLayerNorm(dims[0], eps=1e-6, data_format="channels_first") ) self.downsample_layers.append(stem) for i in range(3): downsample_layer = nn.Sequential( HorLayerNorm(dims[i], eps=1e-6, data_format="channels_first"), nn.Conv2d(dims[i], dims[i+1], kernel_size=2, stride=2), ) self.downsample_layers.append(downsample_layer) self.stages = nn.ModuleList() # 4 feature resolution stages, each consisting of multiples bind residual blocks dummy dp_rates=[x.item() for x in torch.linspace(0, drop_path_rate, sum(depths))] if not isinstance(gnconv, list): gnconv = [gnconv, gnconv, gnconv, gnconv] else: gnconv = gnconv assert len(gnconv) == 4 cur = 0 for i in range(4): stage = nn.Sequential( *[HorBlock(dim=dims[i], drop_path=dp_rates[cur + j], layer_scale_init_value=layer_scale_init_value, gnconv=gnconv[i]) for j in range(depths[i])]# hornet by iscyy/air ) self.stages.append(stage) cur += depths[i] self.apply(self._init_weights) def _init_weights(self, m): if isinstance(m, (nn.Conv2d, nn.Linear)): nn.init.trunc_normal_(m.weight, std=.02) nn.init.constant_(m.bias, 0) def forward(self, x): x = self.downsample_layers[self.index](x) x = self.stages[self.index](x) return x
这是一个名为HorNet的网络类,它继承自nn.Module。HorNet是一个用于目标检测的神经网络,具体实现了一个由ISCYY/YOLOAIR开发的算法。该网络包括主干网络和特征提取网络。
在__init__函数中,HorNet接受一些参数,包括网络输入通道数、网络深度、特征维度等等。其中主干网络是由几个下采样层(downsample_layers)组成,用于将输入的图片进行缩小和特征提取。特征提取网络是由若干个HorBlock组成的,每个HorBlock包括一些卷积层和归一化层,用于提取特征和进行特征的降维和升维。
在forward函数中,HorNet首先通过下采样层将输入的图像进行缩小,然后通过特征提取网络进行特征提取和降维,最终输出特征图。这个特征图可以用于进行目标检测的后续操作,比如目标框预测和类别分类等。
class CSPDarkNet(nn.Module):
CSPDarkNet 是一个深度神经网络模型,它是 YOLOv4 目标检测算法的基础模型之一,其核心是 CSP 模块(Cross Stage Partial Network)。它具有以下特点:
1. 使用 CSP 模块分离卷积计算,减少了计算量和参数数量。
2. 采用 DarkNet53 作为主干网络,具有较高的精度和速度。
3. 通过 SPP、PAN 等技术增强了模型的感受野和多尺度特征表达能力。
4. 基于 YOLOv4 的思想,使用 Mish 激活函数和多尺度训练等技术进一步提升了精度。
下面是 CSPDarkNet 的代码实现:
```python
import torch
import torch.nn as nn
import torch.nn.functional as F
class CSPBlock(nn.Module):
def __init__(self, in_channels, out_channels, n=1, shortcut=True):
super(CSPBlock, self).__init__()
self.shortcut = shortcut
hidden_channels = out_channels // 2
self.conv1 = nn.Conv2d(in_channels, hidden_channels, 1, bias=False)
self.bn1 = nn.BatchNorm2d(hidden_channels)
self.conv2 = nn.Conv2d(in_channels, hidden_channels, 1, bias=False)
self.bn2 = nn.BatchNorm2d(hidden_channels)
self.conv3 = nn.Conv2d(hidden_channels, hidden_channels, 3, padding=1, groups=n, bias=False)
self.bn3 = nn.BatchNorm2d(hidden_channels)
self.conv4 = nn.Conv2d(hidden_channels, hidden_channels, 1, bias=False)
self.bn4 = nn.BatchNorm2d(hidden_channels)
self.conv5 = nn.Conv2d(hidden_channels, hidden_channels, 3, padding=1, groups=n, bias=False)
self.bn5 = nn.BatchNorm2d(hidden_channels)
self.conv6 = nn.Conv2d(hidden_channels, out_channels, 1, bias=False)
self.bn6 = nn.BatchNorm2d(out_channels)
self.act = nn.LeakyReLU(0.1, inplace=True)
def forward(self, x):
if self.shortcut:
shortcut = x
else:
shortcut = 0
x1 = self.conv1(x)
x1 = self.bn1(x1)
x1 = self.act(x1)
x2 = self.conv2(x)
x2 = self.bn2(x2)
x2 = self.act(x2)
x3 = self.conv3(x2)
x3 = self.bn3(x3)
x3 = self.act(x3)
x4 = self.conv4(x3)
x4 = self.bn4(x4)
x4 = self.act(x4)
x5 = self.conv5(x4)
x5 = self.bn5(x5)
x5 = self.act(x5)
x6 = self.conv6(x5)
x6 = self.bn6(x6)
x6 = self.act(x6)
out = torch.cat([x1, x6], dim=1)
return out + shortcut
class CSPDarkNet(nn.Module):
def __init__(self, num_classes=80):
super(CSPDarkNet, self).__init__()
self.stem = nn.Sequential(
nn.Conv2d(3, 32, 3, padding=1, bias=False),
nn.BatchNorm2d(32),
nn.LeakyReLU(0.1, inplace=True),
nn.Conv2d(32, 64, 3, stride=2, padding=1, bias=False),
nn.BatchNorm2d(64),
nn.LeakyReLU(0.1, inplace=True)
)
self.layer1 = nn.Sequential(
CSPBlock(64, 64, n=1, shortcut=False),
*[CSPBlock(64, 64, n=1) for _ in range(1, 3)]
)
self.layer2 = nn.Sequential(
CSPBlock(64, 128, n=2, shortcut=False),
*[CSPBlock(128, 128, n=2) for _ in range(1, 9)]
)
self.layer3 = nn.Sequential(
CSPBlock(128, 256, n=4, shortcut=False),
*[CSPBlock(256, 256, n=4) for _ in range(1, 9)]
)
self.layer4 = nn.Sequential(
CSPBlock(256, 512, n=8, shortcut=False),
*[CSPBlock(512, 512, n=8) for _ in range(1, 5)],
nn.Conv2d(512, 1024, 1, bias=False),
nn.BatchNorm2d(1024),
nn.LeakyReLU(0.1, inplace=True)
)
self.avgpool = nn.AdaptiveAvgPool2d((1, 1))
self.fc = nn.Linear(1024, num_classes)
def forward(self, x):
x = self.stem(x)
x = self.layer1(x)
x = self.layer2(x)
x = self.layer3(x)
x = self.layer4(x)
x = self.avgpool(x)
x = x.view(x.size(0), -1)
x = self.fc(x)
return x
```