otto-group-product-classification-challenge（Pytorch处理多分类问题）

注意：使用的数据来自kaggle，链接

由于上面给出的两个参考链接，对代码的讲解都已经很详细，所以这里不再赘述，下面按自己的理解整理了代码如下：

Imports

import numpy as np
import pandas as pd
import os
import time
from xgboost import XGBClassifier
import matplotlib.pyplot as plt
import torch
from torch.utils.data import Dataset, DataLoader
import torch.nn as nn
import torch.nn.functional as F
import torch.optim as optim

Prepare Data

# 处理数据
csv_path = os.path.join('train.csv')
datas = pd.read_csv(csv_path)
datas = datas.copy() 
datas = datas.drop(columns='id')
datas = datas.sample(frac=1)

# 将category转化为数字
datas.target = datas.target.astype('category').cat.codes

# 划分数据集
rows, _ = datas.shape  # type(datas) 为 <class 'pandas.core.frame.DataFrame'>
train_rows = int(rows*0.7)
train_datas = datas.iloc[:train_rows, :]
val_datas = datas.iloc[train_rows:, :]

# 得到features和targets
train_features = train_datas.loc[:, train_datas.columns!='target'].values  # values 得到一个矩阵
train_targets = train_datas.target.values

val_features = val_datas.loc[:, val_datas.columns!='target'].values
val_targets = val_datas.target.values

# 封装 继承dataset
class CustomDataset(Dataset):
    def __init__(self, features, targets):
        super(CustomDataset, self).__init__()
        
        self.features = features
        self.targets = targets
    
    def __len__(self):
        return len(self.features)
    
    def __getitem__(self, idx):
        return self.features[idx], self.targets[idx]


# 得到Dataset类
train_ds = CustomDataset(train_features, train_targets)
val_ds = CustomDataset(val_features, val_targets)

# 得到DataLoader
batch_size = 64
train_loader = DataLoader(train_ds, batch_size=batch_size)
val_loader = DataLoader(val_ds, batch_size=batch_size)

Device

device = torch.device('cuda' if torch.cuda.is_available() else 'cpu')

Design Model

class Net(torch.nn.Module):
    def __init__(self):
        super(Net, self).__init__()
        
        self.l1 = torch.nn.Linear(93, 64)
        self.bn = torch.nn.BatchNorm1d(num_features=64)
        self.l2 = torch.nn.Linear(64, 32)
        self.dropout = torch.nn.Dropout(p=0.1)
        self.l3 = torch.nn.Linear(32, 16)
        self.l4 = torch.nn.Linear(16, 9)
    
    def forward(self, x):
        # first layer
        x = self.l1(x)
        x = self.bn(x)
        x = torch.relu(x)
        # second layer
        x = self.l2(x)
        x = self.dropout(x)
        x = torch.relu(x)
        
        x = torch.relu(self.l3(x))
        return self.l4(x)  # 注意 这里不要加relu

model = Net().to(device)

Construct Loss and Optimizer

criterion = torch.nn.CrossEntropyLoss().to(device)
optimizer = torch.optim.SGD(model.parameters(), lr=0.01, momentum=0.5)

Train and Validate

def train():
    losses = 0.0
    accs = 0.0
    for idx, data in enumerate(train_loader, 0):
        inputs, targets = data
        inputs = inputs.to(device)
        targets = targets.to(device)
        optimizer.zero_grad()
        
        # forward + backward + update
        outputs = model(inputs.float())
        loss = criterion(outputs, targets.long())
        loss.backward()
        optimizer.step()
        
        losses += loss.item()
        _, predicted = torch.max(outputs.data, dim=1)
        accs += (predicted==targets).sum().item()
        
    losses /= len(train_loader)
    accs = accs * 100 / len(train_ds)
    print('Training:  loss: %.2f    accuracy: %.2f %%' %(losses, accs))
    
    return losses, accs

def val():
    losses = 0.0
    accs = 0.0
    with torch.no_grad():
        for data in val_loader:
            inputs, labels = data
            inputs = inputs.to(device)
            labels = labels.to(device)
            outputs = model(inputs.float())
            losses += criterion(outputs, labels.long()).item()
            _, predicted = torch.max(outputs.data, dim=1)
            accs += (predicted == labels).sum().item()
    losses /= len(val_loader)
    accs = accs * 100 / len(val_ds)
    print('Validating:   loss: %.2f    accuracy: %.2f %%' %(losses, accs))
    
    return losses, accs

train_losses = []
val_losses = []
train_accs = []
val_accs = []
maxAcc = 0  # 记录最高准确率

for epoch in range(100):
    print('[epoch: %d]' % (epoch+1))
    
    losses, accs = train()
    train_losses.append(losses)
    train_accs.append(accs)
    
    losses, accs = val()
    val_losses.append(losses)
    val_accs.append(accs)
    
    if maxAcc < accs:
        maxAcc = accs
    
    check = np.greater(maxAcc, val_accs[-5:])
    if (check.all()==True)  and (epoch>20):
        print('Convergence met!
')
        break

print('Maximum validation accuracy: %.2f %%' % (maxAcc))

Plot Losses

# 这里采用了指数平滑
import math
import matplotlib.pyplot as plt

tmp_train_losses = [math.e**i for i in train_losses]
tmp_val_losses = [math.e**i for i in val_losses]
plt.figure(figsize=(10, 5))
plt.plot(tmp_train_losses, 'r', label='Training')
plt.plot(tmp_val_losses, 'b', label='Validating')
plt.xlabel('Epoch')
plt.ylabel('Loss per epoch')
plt.legend()
plt.show()