DL 基础：PyTorch 常用代码存档

1 pandas 读 csv

import torch
from torch import nn
import numpy as np
import pandas as pd
from copy import deepcopy
device = "cuda" if torch.cuda.is_available() else "cpu"

# 读 csv
data_all = pd.read_csv('./CFD_data/record_data0.csv')
# 提取某一列
colume = np.array(data_all[['colume_name']], dtype=np.float32).reshape(-1, 1)
# 提取某一个值
value = data[data['食物种类']=='主食']['卡路里'].item()
# 数据操作
c = np.concatenate([a[1:], b[:-1]], axis=1)
c = torch.cat([a, b], axis=1)
# 存 csv
c.to_csv('./CFD_data/flow_rate.csv', index=False)

2 NN 的搭建、训练与评估

搭建：使用 nn.Sequential 。

# model
NN_model = nn.Sequential(
    nn.Linear(6, 256), 
    nn.ReLU(),
    nn.Linear(256, 256),
    nn.ReLU(),
    nn.Linear(256, 256),
    nn.ReLU(),
    nn.Linear(256, 1),
)
# 优化器
optimizer = torch.optim.Adam(NN_model.parameters(), lr=0.001)

训练：

def NN_train(train_x, train_y, model, loss_fn, optimizer, epoches, batch_size, save_path):
    """
    训练网络
    输入:
        train_x, train_y:   训练集
        model:              网络模型
        loss_fn:            损失函数
        optimizer:          优化器
        epoches:            epoches 个数
        batch_size:         mini batch 大小
        save_path:          模型保存路径
    """
    # 切换到train模式
    model.train()
    losses = []
    for epoch in range(epoches):
        batch_loss = []
        for start in range(0, len(train_x), batch_size): # mini batch
            end = start + batch_size if start + batch_size < len(train_x) else len(train_x)
            xx = torch.tensor(train_x[start:end], dtype=torch.float, requires_grad=True)
            yy = torch.tensor(train_y[start:end], dtype=torch.float, requires_grad=True)
            xx, yy = xx.to(device), yy.to(device) # 加载到 device
            pred = model(xx) # 输入数据到模型里得到输出
            loss = loss_fn(pred, yy) # 计算输出和标签的 loss           
            optimizer.zero_grad() # 清零
            loss.backward() # 反向推导
            optimizer.step() # 步进优化器
            batch_loss.append(loss.data.numpy())
        if epoch % max(1, epoches//8) == 0:
            print(f"Training Error in epoch {epoch}: {np.mean(batch_loss):>8f}")
    torch.save(model.state_dict(), save_path) # 保存模型

测试：

def NN_test(test_x, test_y, model, save_path, loss_fn):
    """
    测试网络
    输入:
        test_x, test_y:     测试集
        model:              网络模型
        loss_fn:            损失函数
        save_path:          模型保存路径
    """
    model.load_state_dict(torch.load(save_path)) # 加载模型  
    model.eval() # 切换到测试模型
    MSE_loss_fn = nn.MSELoss() # MSE loss function
    test_loss, MSE = 0, 0 # 记录 loss 和 MSE
    # 梯度截断
    with torch.no_grad():
        test_x, test_y = torch.tensor(test_x).to(device), torch.tensor(test_y).to(device) # 加载到 device
        pred = model(test_x) # 输入数据到模型里得到输出
        test_loss = loss_fn(pred, test_y).item() # 计算输出和标签的 loss
        MSE = MSE_loss_fn(pred, test_y).item() # MSE
    print(f"Test Error: \n  Avg loss: {test_loss:>8f}, MSE: {MSE:>8f}\n")
    print(f"Test Result: \n  Prediction: {pred[:5]}, \n  Y: {test_y[:5]}, \n  diff: {test_y[:5]-pred[:5]}\n")

测试 ensemble model（平均值）：

def NN_test_ensemble(test_x, test_y, loaded_model_list, loss_fn):
    for model in loaded_model_list:
        model.eval() # 切换到测试模型
    MSE_loss_fn = nn.MSELoss() # MSE loss function
    test_loss, MSE = 0, 0 # 记录 loss 和 MSE
    # 梯度截断
    with torch.no_grad():
        test_x, test_y = torch.tensor(test_x).to(device), torch.tensor(test_y).to(device) # 加载到 device
        pred = torch.zeros(test_y.shape)
        for model in loaded_model_list:
            pred += model(test_x) # 输入数据到模型里得到输出
        pred /= len(loaded_model_list)
        test_loss = loss_fn(pred, test_y).item() # 计算输出和标签的 loss
        MSE = MSE_loss_fn(pred, test_y).item() # MSE
    print(f"Test Error: \n  Avg loss: {test_loss:>8f}, MSE: {MSE:>8f}\n")
    print(f"Test Result: \n  Prediction: {pred[:5]}, \n  Y: {test_y[:5]}, \n  diff: {test_y[:5]-pred[:5]}\n")