首页分享 Pytorch采用AlexNet实现猫狗数据集分类（训练与预测）

Pytorch采用AlexNet实现猫狗数据集分类（训练与预测）

来源：萌宠菠菠乐园时间：2024-09-26 07:30

Pytorch采用AlexNet实现猫狗数据集分类（训练与预测）介绍AlexNet网络模型猫狗数据集AlexNet网络训练训练全代码预测预测图片

介绍

AlexNet模型是CNN网络中经典的网络模型，适合初学者学习，本文对AlexNet结构参数初步说明，详细可以下载论文。通过AlexNet对Kaggle的猫狗数据集进行训练和预测，相关资料为搜集总结。 1

AlexNet网络模型

AlexNet网络结构
如图是2012年AlexNet网络模型结构，由于之前GPU内存小，当时网络是采用了两块GPU，现在训练是不需要的，AlexNet的特点归纳为以下几点：

网络结构 ，包括五个卷积层，三个池化层，三个全连接层；激活函数，采用Relu函数，优点是：网络训练更快；防止梯度消失；使得网络更具稀疏性；池化层，采用最大值池化Max pooling，一个像素表示一块区域的像素值，降低图像分辨率；池化层虽然没有可以学习参数，也相当于另类卷积层；训练技巧，（1）采用数据增强，对训练阶段和测试阶段的数据都进行了增强，包括针对位置的裁剪和针对颜色的扰动。在其结论中，颜色扰动效果有限，尺度扰动有不错的效果；（2）采用了随机失活Dropout，使得权值按P的概率失活，达到防止过拟合的目的。

猫狗数据集

Kaggle猫狗数据集，可以直接在官网下载https://www.kaggle.com/c/dogs-vs-cats-redux-kernels-edition/data。下载的压缩包解压后，如图：
解压后三个文件
train是25000张猫狗图片，各占一半，图片名字都进行了标记，由于在同一个文件中，在数据处理阶段，需要打乱图片顺序以及读取图片名对其进行标记分类。训练阶段，只需要用到train文件的图片，首先写个dataset方便图片读取和相关操作，文件命名为My_dataset.py.

import os import random from PIL import Image from torch.utils.data import Dataset random.seed(1) class CatDogDataset(Dataset): def __init__(self, data_dir, mode="train", split_n=0.9, rng_seed=620, transform=None): """ rmb面额分类任务的Dataset :param data_dir: str, 数据集所在路径 :param transform: torch.transform，数据预处理 """ self.mode = mode self.data_dir = data_dir self.rng_seed = rng_seed self.split_n = split_n self.data_info = self._get_img_info() # data_info存储所有图片路径和标签，在DataLoader中通过index读取样本 self.transform = transform def __getitem__(self, index): path_img, label = self.data_info[index] img = Image.open(path_img).convert('RGB') # 0~255 if self.transform is not None: img = self.transform(img) # 在这里做transform，转为tensor等等 return img, label def __len__(self): if len(self.data_info) == 0: raise Exception("ndata_dir:{} is a empty dir! Please checkout your path to images!".format(self.data_dir)) return len(self.data_info) def _get_img_info(self): img_names = os.listdir(self.data_dir) img_names = list(filter(lambda x: x.endswith('.jpg'), img_names)) random.seed(self.rng_seed) random.shuffle(img_names) img_labels = [0 if n.startswith('cat') else 1 for n in img_names] split_idx = int(len(img_labels) * self.split_n) # 25000* 0.9 = 22500 # split_idx = int(100 * self.split_n) if self.mode == "train": img_set = img_names[:split_idx] # 数据集90%训练 # img_set = img_names[:22500] # hard code 数据集90%训练 label_set = img_labels[:split_idx] elif self.mode == "valid": img_set = img_names[split_idx:] label_set = img_labels[split_idx:] else: raise Exception("self.mode 无法识别，仅支持(train, valid)") path_img_set = [os.path.join(self.data_dir, n) for n in img_set] data_info = [(n, l) for n, l in zip(path_img_set, label_set)] return data_info

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AlexNet网络训练

在开始网络搭建前，还需的准备工作：
为了提高模型分类准确度，引入AlexNet在ImageNet比赛时的预训练模型，AlexNet结构就不重写了，直接调用Pytorch中的预设模型，AlexNet最后全连接层是1000分类的，所以之后代码中还需要修改最后一层参数。
链接：https://pan.baidu.com/s/16xd6PjmjPrAKIbta81yUdw
提取码：cyh9
简单的函数对预训练模型读取。

def get_model(path_state_dict, vis_model=False): """ 创建模型，加载参数 :param path_state_dict: :return: """ model = models.alexnet() pretrained_state_dict = torch.load(path_state_dict) model.load_state_dict(pretrained_state_dict) if vis_model: from torchsummary import summary summary(model, input_size=(3, 224, 224), device="cpu") model.to(device) return model

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训练全代码

import os import numpy as np import torch.nn as nn import torch from torch.utils.data import DataLoader import torchvision.transforms as transforms import torch.optim as optim from matplotlib import pyplot as plt import torchvision.models as models from A_alexnet.tools.my_dataset import CatDogDataset BASE_DIR = os.path.dirname(os.path.abspath(__file__)) device = torch.device("cuda" if torch.cuda.is_available() else "cpu") def get_model(path_state_dict, vis_model=False): """ 创建模型，加载参数 :param path_state_dict: :return: """ model = models.alexnet() pretrained_state_dict = torch.load(path_state_dict) model.load_state_dict(pretrained_state_dict) if vis_model: from torchsummary import summary summary(model, input_size=(3, 224, 224), device="cpu") model.to(device) return model if __name__ == "__main__": # config data_dir = os.path.join(BASE_DIR, "..", "data", "train") # 读取预训练模型 path_state_dict = os.path.join(BASE_DIR, "..", "data", "alexnet-owt-4df8aa71.pth") # 二分类，设置类为2 num_classes = 2 MAX_EPOCH = 3 # 可自行修改,设置大效果会好点 BATCH_SIZE = 200 # 可自行修改,内存大可以设置大点,速度快点 LR = 0.001 # 可自行修改 log_interval = 1 # 可自行修改 val_interval = 1 # 可自行修改 classes = 2 start_epoch = -1 lr_decay_step = 1 # 可自行修改 # ============================ step 1/5 数据 ============================ norm_mean = [0.485, 0.456, 0.406] norm_std = [0.229, 0.224, 0.225] train_transform = transforms.Compose([ transforms.Resize((256)), # (256, 256) 区别 transforms.CenterCrop(256), transforms.RandomCrop(224), transforms.RandomHorizontalFlip(p=0.5), transforms.ToTensor(), transforms.Normalize(norm_mean, norm_std), ]) normalizes = transforms.Normalize(norm_mean, norm_std) valid_transform = transforms.Compose([ transforms.Resize((256, 256)), transforms.TenCrop(224, vertical_flip=False), transforms.Lambda(lambda crops: torch.stack([normalizes(transforms.ToTensor()(crop)) for crop in crops])), ]) # 构建MyDataset实例 train_data = CatDogDataset(data_dir=data_dir, mode="train", transform=train_transform) valid_data = CatDogDataset(data_dir=data_dir, mode="valid", transform=valid_transform) # 构建DataLoder train_loader = DataLoader(dataset=train_data, batch_size=BATCH_SIZE, shuffle=True) valid_loader = DataLoader(dataset=valid_data, batch_size=4) # ============================ step 2/5 模型 ============================ alexnet_model = get_model(path_state_dict, False) num_ftrs = alexnet_model.classifier._modules["6"].in_features alexnet_model.classifier._modules["6"] = nn.Linear(num_ftrs, num_classes) alexnet_model.to(device) # ============================ step 3/5 损失函数 ============================ criterion = nn.CrossEntropyLoss() # ============================ step 4/5 优化器 ============================ optimizer = optim.SGD(alexnet_model.parameters(), lr=LR, momentum=0.9) # 选择优化器 scheduler = torch.optim.lr_scheduler.StepLR(optimizer, step_size=lr_decay_step, gamma=0.1) # 设置学习率下降策略 # ============================ step 5/5 训练 ============================ train_curve = list() valid_curve = list() for epoch in range(start_epoch + 1, MAX_EPOCH): loss_mean = 0. correct = 0. total = 0. alexnet_model.train() for i, data in enumerate(train_loader): # if i > 1: # break # forward inputs, labels = data inputs, labels = inputs.to(device), labels.to(device) outputs = alexnet_model(inputs) # backward optimizer.zero_grad() loss = criterion(outputs, labels) loss.backward() # update weights optimizer.step() # 统计分类情况 _, predicted = torch.max(outputs.data, 1) total += labels.size(0) correct += (predicted == labels).squeeze().cpu().sum().numpy() # 打印训练信息 loss_mean += loss.item() train_curve.append(loss.item()) if (i+1) % log_interval == 0: loss_mean = loss_mean / log_interval print("Training:Epoch[{:0>3}/{:0>3}] Iteration[{:0>3}/{:0>3}] Loss: {:.4f} Acc:{:.2%}".format( epoch, MAX_EPOCH, i+1, len(train_loader), loss_mean, correct / total)) loss_mean = 0. scheduler.step() # 更新学习率 # validate the model if (epoch+1) % val_interval == 0: correct_val = 0. total_val = 0. loss_val = 0. alexnet_model.eval() with torch.no_grad(): for j, data in enumerate(valid_loader): inputs, labels = data inputs, labels = inputs.to(device), labels.to(device) bs, ncrops, c, h, w = inputs.size() # [4, 10, 3, 224, 224 outputs = alexnet_model(inputs.view(-1, c, h, w)) outputs_avg = outputs.view(bs, ncrops, -1).mean(1) loss = criterion(outputs_avg, labels) _, predicted = torch.max(outputs_avg.data, 1) total_val += labels.size(0) correct_val += (predicted == labels).squeeze().cpu().sum().numpy() loss_val += loss.item() loss_val_mean = loss_val/len(valid_loader) valid_curve.append(loss_val_mean) print("Valid:t Epoch[{:0>3}/{:0>3}] Iteration[{:0>3}/{:0>3}] Loss: {:.4f} Acc:{:.2%}".format( epoch, MAX_EPOCH, j+1, len(valid_loader), loss_val_mean, correct_val / total_val)) alexnet_model.train() train_x = range(len(train_curve)) train_y = train_curve train_iters = len(train_loader) valid_x = np.arange(1, len(valid_curve)+1) * train_iters*val_interval # 由于valid中记录的是epochloss，需要对记录点进行转换到iterations valid_y = valid_curve # 保存网络模型及参数 torch.save(alexnet_model.state_dict(), 'whole_CatDog_params.pth') plt.plot(train_x, train_y, label='Train') plt.plot(valid_x, valid_y, label='Valid') plt.legend(loc='upper right') plt.ylabel('loss value') plt.xlabel('Iteration') plt.show()

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运行训练代码，就开始计算。

一般设置3个epoch，训练集和验证集准确率都在96%以上。

注意：在代码中，torch.save(alexnet_model.state_dict(), ‘whole_CatDog_params.pth’)已经保存了最终训练模型及参数，路径就自己设置，这里我直接保存。

预测

import os os.environ['NLS_LANG'] = 'SIMPLIFIED CHINESE_CHINA.UTF8' import time import json import torch import torchvision.transforms as transforms from PIL import Image from matplotlib import pyplot as plt import torchvision.models as models BASE_DIR = os.path.dirname(os.path.abspath(__file__)) device = torch.device("cuda" if torch.cuda.is_available() else "cpu") def img_transform(img_rgb, transform=None): """ 将数据转换为模型读取的形式 :param img_rgb: PIL Image :param transform: torchvision.transform :return: tensor """ if transform is None: raise ValueError("找不到transform！必须有transform对img进行处理") img_t = transform(img_rgb) return img_t def load_class_names(p_clsnames, p_clsnames_cn): """ 加载标签名 :param p_clsnames: :param p_clsnames_cn: :return: """ with open(p_clsnames, "r") as f: class_names = json.load(f) with open(p_clsnames_cn, encoding='UTF-8') as f: # 设置文件对象 class_names_cn = f.readlines() return class_names, class_names_cn def get_model(path_state_dict, num_classes, vis_model=False): """ 创建模型，加载参数 :param path_state_dict: :return: """ model = models.alexnet(num_classes=num_classes) pretrained_state_dict = torch.load(path_state_dict) model.load_state_dict(pretrained_state_dict) model.eval() if vis_model: from torchsummary import summary summary(model, input_size=(3, 224, 224), device="cpu") model.to(device) return model def process_img(path_img): # hard code norm_mean = [0.485, 0.456, 0.406] norm_std = [0.229, 0.224, 0.225] inference_transform = transforms.Compose([ transforms.Resize(256), transforms.CenterCrop((224, 224)), transforms.ToTensor(), transforms.Normalize(norm_mean, norm_std), ]) # path --> img img_rgb = Image.open(path_img).convert('RGB') # img --> tensor img_tensor = img_transform(img_rgb, inference_transform) img_tensor.unsqueeze_(0) # chw --> bchw img_tensor = img_tensor.to(device) return img_tensor, img_rgb if __name__ == "__main__": num_classes=2 # config path_state_dict = os.path.join(BASE_DIR, "whole_CatDog_params_0909.pth") path_img = os.path.join(BASE_DIR, "..", "data", "272.jpg") # 1/5 load img img_tensor, img_rgb = process_img(path_img) # 2/5 load model alexnet_model = get_model(path_state_dict,num_classes, True) with torch.no_grad(): time_tic = time.time() outputs = alexnet_model(img_tensor) time_toc = time.time() # 4/5 index to class names _, pred_int = torch.max(outputs.data, 1) _, top1_idx = torch.topk(outputs.data, 1, dim=1) # pred_idx = int(pred_int.cpu().numpy()) if pred_idx == 0: pred_str= str("cat") print("img: {} is: {}".format(os.path.basename(path_img), pred_str)) else: pred_str = str("dog") print("img: {} is: {}".format(os.path.basename(path_img), pred_str)) print("time consuming:{:.2f}s".format(time_toc - time_tic)) # 5/5 visualization plt.imshow(img_rgb) plt.title("predict:{}".format(pred_str)) plt.text(5, 45, "top {}:{}".format(1, pred_str), bbox=dict(fc='yellow')) plt.show()

预测模型有需要注意的地方，是get_model直接修改最后全连接层的分类数为2，跟训练修改方法不一致。用训练模型的修改方法不知道为啥一直有bug，水平有限就直接换了方法修改。预测模型没有全导入test的照片预测，只是截取一张预测一个结果，感兴趣可以自行导入全部test照片。
预测结果
推荐使用torchsummary，结果可以很直观看到网络结构及相关参数。直接pip install torchsummary就可以安装了。