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pytorch版Class-Balanced Loss训练模型
一、数据准备
二、模型训练
三、模型预测
总结

pytorch版Class-Balanced Loss训练模型

论文地址：https://arxiv.org/pdf/1901.05555.pdf

一、数据准备

将自己的数据集按照一下格式进行准备
执行以下代码进行数据集划分

执行以下代码进行数据集划分

def split_dataset(dataset, split_fraction=0.9):classes = [d for d in os.listdir(dataset) if os.path.isdir(os.path.join(dataset, d))]train_data_dir = os.path.join(dataset, 'train')test_data_dir = os.path.join(dataset, 'test')if os.path.exists(train_data_dir) and os.path.exists(test_data_dir):shutil.rmtree(train_data_dir)shutil.rmtree(test_data_dir)os.makedirs(train_data_dir)os.makedirs(test_data_dir)for cls in classes:dr = os.path.join(dataset, cls)cls_samples = [f for f in os.listdir(dr) if os.path.isfile(os.path.join(dr, f))]train_samples = random.sample(cls_samples, int(np.ceil(len(cls_samples) * split_fraction)))test_samples = [s for s in cls_samples if s not in train_samples]os.mkdir(os.path.join(dataset, 'train', cls))os.mkdir(os.path.join(dataset, 'test', cls))for s in train_samples:shutil.copy(os.path.join(dr, s), os.path.join(dataset, 'train', cls))for s in test_samples:shutil.copy(os.path.join(dr, s), os.path.join(dataset, 'test', cls))return train_data_dir, test_data_dir

划分完训练集和测试集合之后进行训练数据的生成，train文件夹运行一次，test文件夹运行一次，生成train.txt和text.txt.

origin_dir = '/mnt/cecilia/all/train'
cls_dir_list = sorted(os.listdir(origin_dir))
f = open('/mnt/cecilia/class.txt', 'a')
cls_list = []
for i,cls in enumerate(cls_dir_list):cls_list.append(cls)f.write(str(cls_list))img_list = glob.glob(os.path.join(origin_dir, cls, '*'))print('cls',cls)for img in  img_list:f.write(f'{img},{i}\n')

另外还要生成一个每个类别对应的图片数量txt，列表形式[10,20,…]
训练的时候的class_index需要和类别下文件数量列表对应起来。

二、模型训练

import torch.optim as optim
import torchvision
import torchvision.transforms as transforms
import argparse
import os
from torchvision import modelsfrom torch.utils.data import Dataset, DataLoader
import numpy as np
from torch.optim import lr_scheduler
from PIL import Image
from torch.autograd import Variableimport torch
import torch.nn as nn
import torch.nn.functional as F
import torch.nn.init as initfrom torch.autograd import VariableNO_OF_CLASSES = 2388def focal_loss(labels, logits, alpha, gamma):"""Compute the focal loss between `logits` and the ground truth `labels`.Focal loss = -alpha_t * (1-pt)^gamma * log(pt)where pt is the probability of being classified to the true class.pt = p (if true class), otherwise pt = 1 - p. p = sigmoid(logit).Args:labels: A float tensor of size [batch, num_classes].logits: A float tensor of size [batch, num_classes].alpha: A float tensor of size [batch_size]specifying per-example weight for balanced cross entropy.gamma: A float scalar modulating loss from hard and easy examples.Returns:focal_loss: A float32 scalar representing normalized total loss."""BCLoss = F.binary_cross_entropy_with_logits(input = logits, target = labels,reduction = "none")if gamma == 0.0:modulator = 1.0else:modulator = torch.exp(-gamma * labels * logits - gamma * torch.log(1 +torch.exp(-1.0 * logits)))loss = modulator * BCLossweighted_loss = alpha * lossfocal_loss = torch.sum(weighted_loss)focal_loss /= torch.sum(labels)return focal_lossdef CB_loss(labels, logits, samples_per_cls, no_of_classes, loss_type, beta, gamma):"""Compute the Class Balanced Loss between `logits` and the ground truth `labels`.Class Balanced Loss: ((1-beta)/(1-beta^n))*Loss(labels, logits)where Loss is one of the standard losses used for Neural Networks.Args:labels: A int tensor of size [batch].logits: A float tensor of size [batch, no_of_classes].samples_per_cls: A python list of size [no_of_classes].no_of_classes: total number of classes. intloss_type: string. One of "sigmoid", "focal", "softmax".beta: float. Hyperparameter for Class balanced loss.gamma: float. Hyperparameter for Focal loss.Returns:cb_loss: A float tensor representing class balanced loss"""#effective_num = 1.0 - np.power(beta, samples_per_cls)#weights = (1.0 - beta) / np.array(effective_num)#weights = weights / np.sum(weights) * int(NO_OF_CLASSES)weights = np.array([1])*NO_OF_CLASSES labels_one_hot = F.one_hot(labels, no_of_classes).float().cuda()# print(labels_one_hot.shape)weights = torch.tensor(weights).float()# 增加维度weights = weights.unsqueeze(0).cuda()weights = weights.repeat(labels_one_hot.shape[0], 1) * labels_one_hotweights = weights.sum(1)weights = weights.unsqueeze(1)weights = weights.repeat(1, no_of_classes)# print('=====weights=====',weights)if loss_type == "focal":cb_loss = focal_loss(labels_one_hot, logits, weights, gamma)elif loss_type == "sigmoid":cb_loss = F.binary_cross_entropy_with_logits(input=logits, target=labels_one_hot, weight=weights)elif loss_type == "softmax":pred = logits.softmax(dim=1)cb_loss = F.binary_cross_entropy(input=pred, target=labels_one_hot, weight=weights)else:cb_loss = Nonereturn cb_lossdef default_loader(path):return Image.open(path).convert('RGB')class MyDataset(Dataset):def __init__(self, txt, transform=None, target_transform=None, loader=default_loader):fh = open(txt, 'r')imgs = []for line in fh:line = line.strip('\n')line = line.rstrip()words = line.split(',')imgs.append((words[0], int(words[1])))self.imgs = imgsself.transform = transformself.target_transform = target_transformself.loader = loaderdef __getitem__(self, index):fn, label = self.imgs[index]img = self.loader(fn)if self.transform is not None:img = self.transform(img)return img, labeldef __len__(self):return len(self.imgs)def target_transform(label):label = np.array(label)target = torch.from_numpy(label).long()return target# 定义是否使用GPU
device = torch.device("cuda" if torch.cuda.is_available() else "cpu")
# device = 'cpu'
# 参数设置,使得我们能够手动输入命令行参数，就是让风格变得和Linux命令行差不多
parser = argparse.ArgumentParser(description='PyTorch CIFAR10 Training')
parser.add_argument('--outf', default='./model/', help='folder to output images and model checkpoints')  # 输出结果保存路径
args = parser.parse_args()# 超参数设置
EPOCH = 100  # 遍历数据集次数
pre_epoch = 0  # 定义已经遍历数据集的次数
BATCH_SIZE = 64  # 批处理尺寸(batch_size)
LR = 0.1  # 学习率# 准备数据集并预处理
transform_train = transforms.Compose([transforms.Resize([144, 144]),transforms.CenterCrop([128, 128]),transforms.ToTensor(),transforms.Normalize((0.5, 0.5, 0.5), (0.5, 0.5, 0.5)),  # R,G,B每层的归一化用到的均值和方差
])transform_test = transforms.Compose([transforms.Resize((128, 128)),transforms.ToTensor(),transforms.Normalize((0.5, 0.5, 0.5), (0.5, 0.5, 0.5)),
])train_data = MyDataset(txt='/mnt/cecilia/train.txt', transform=transform_train)
test_data = MyDataset(txt='/mnt/cecilia/test.txt', transform=transform_test)trainloader = DataLoader(dataset=train_data, batch_size=BATCH_SIZE, shuffle=True)
testloader = DataLoader(dataset=test_data, batch_size=BATCH_SIZE)# 模型定义-ResNet
net = models.resnet34(pretrained=True).to(device)
net.fc = nn.Sequential(nn.Linear(512, NO_OF_CLASSES)).to(device)# 定义损失函数和优化方式
optimizer = optim.SGD(net.parameters(), lr=LR, momentum=0.9,weight_decay=5e-4)  # 优化方式为mini-batch momentum-SGD，并采用L2正则化（权重衰减）
scheduler = lr_scheduler.MultiStepLR(optimizer, [50, 80], 0.1)# 训练
if __name__ == "__main__":cls_num = eval(open('/mnt/cecilia/num.txt', 'r').read())num = np.array(cls_num)if not os.path.exists(args.outf):os.makedirs(args.outf)best_acc = 0  # 2 初始化best test accuracyprint("Start Training, Resnet-34!")  # 定义遍历数据集的次数with open("acc.txt", "w") as f:with open("log.txt", "w")as f2:for epoch in range(pre_epoch, EPOCH):scheduler.step()print('\nEpoch: %d' % (epoch + 1))net.train()sum_loss = 0.0correct = 0.0total = 0.0for i, data in enumerate(trainloader, 0):# 准备数据length = len(trainloader)inputs, labels = datainputs, labels = inputs.to(device), labels.to(device)optimizer.zero_grad()# forward + backwardoutputs = net(inputs).to(device)# print('=====outputs=====',outputs)loss = CB_loss(labels=labels, logits=outputs,samples_per_cls=num, no_of_classes=NO_OF_CLASSES,loss_type="sigmoid", beta=0.9999, gamma=1)loss.backward()optimizer.step()# 每训练1个batch打印一次loss和准确率sum_loss += loss.item()_, predicted = torch.max(outputs.data, 1)total += labels.size(0)correct += predicted.eq(labels.data).cpu().sum()print('[epoch:%d, iter:%d] Loss: %.03f | Acc: %.3f%% | Lr: %.03f'% (epoch + 1, (i + 1 + epoch * length), sum_loss / (i + 1),100. * float(correct) / total, optimizer.state_dict()['param_groups'][0]['lr']))f2.write('%03d  %05d |Loss: %.03f | Acc: %.3f%% | Lr: %.03f'% (epoch + 1, (i + 1 + epoch * length), sum_loss / (i + 1),100. * float(correct) / total, optimizer.state_dict()['param_groups'][0]['lr']))f2.write('\n')f2.flush()# 每训练完一个epoch测试一下准确率print("Waiting Test!")with torch.no_grad():correct = 0total = 0for data in testloader:net.eval()images, labels = dataimages, labels = images.to(device), labels.to(device)outputs = net(images)# 取得分最高的那个类 (outputs.data的索引号)_, predicted = torch.max(outputs.data, 1)total += labels.size(0)correct += (predicted == labels).sum()print('测试分类准确率为：%.3f%%' % (100 * float(correct) / total))acc = 100. * float(correct) / totalif (epoch + 1) % 1 == 0:# 将每次测试结果实时写入acc.txt文件中print('Saving model......')torch.save(net.state_dict(), '%s/net_%03d.pth' % (args.outf, epoch + 1))f.write("EPOCH=%03d,Accuracy= %.3f%%| Lr: %.03f" % (epoch + 1, acc,optimizer.state_dict()['param_groups'][0]['lr']))f.write('\n')f.flush()# 记录最佳测试分类准确率并写入best_acc.txt文件中if acc > best_acc:f3 = open("best_acc.txt", "w")f3.write("EPOCH=%d,best_acc= %.3f%%" % (epoch + 1, acc))f3.close()best_acc = accprint("Training Finished, TotalEPOCH=%d" % EPOCH)

执行该段代码即可进行模型的训练。

三、模型预测

from torchvision import models
import torchvision.transforms as transforms
import os
import glob
import copy
import cv2
import random
import numpy as np
import shutil
import torch
import shutil
from PIL import Image
import torch.nn as nn
import torch.nn.functional as F
import numpy as np
import pandas as pd
device = torch.device('cuda' if torch.cuda.is_available() else 'cpu')
transform = transforms.Compose([transforms.Resize((128, 128)),transforms.ToTensor(),transforms.Normalize((0.5, 0.5, 0.5), (0.5, 0.5, 0.5)),
])
net = models.resnet34(pretrained=True).to(device)
net.fc = nn.Sequential(nn.Linear(512, 2388)).to(device)
torch.no_grad()
PATH = '/data/net_091.pth'
model_dict=torch.load(PATH)
model_dict=net.load_state_dict(torch.load(PATH))
net.eval()
old = sorted(os.listdir('/data/all/test'))
image_cls_acc = {}
num = 0
for i,cls in enumerate(old):
#     if cls != '飘柔滋润去屑洗发露400':
#         continueimg_list = glob.glob(os.path.join('/data/all/test', cls, '*'))for img_path in img_list:img =  Image.open(img_path).convert('RGB')img_ = transform(img).unsqueeze(0)img_ = img_.to(device)outputs = net(img_).cpu().detach().numpy()[0]
#         print('outputs',outputs)top1_index = np.argmax(outputs)top5_list =list(outputs.argsort()[-5:])print('outputs',i,top1_index,)if cls not in image_cls_acc:image_cls_acc[cls] = [1, 0, 0]if int(i) == int(top1_index) :image_cls_acc[cls][1] += 1if int(i) in top5_list:image_cls_acc[cls][2] += 1else:image_cls_acc[cls][0] += 1if int(i) == int(top1_index):image_cls_acc[cls][1] += 1if int(i) in top5_list:image_cls_acc[cls][2] += 1num += 1

总结

先转过来，有空重新把这个代码优化一下。

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pytorch训练Class-Balanced Loss

1.