社区网站建设方案ppt,网站 备案 中国 名字,多种网站模板,详情图模板介绍#xff1a;上一期介绍了如何利用PyTorch Lightning搭建并训练一个模型#xff08;仅使用训练集#xff09;#xff0c;为了保证模型可以泛化到未见过的数据上#xff0c;数据集通常被分为训练和测试两个集合#xff0c;测试集与训练集相互独立#xff0c;用以测试模… 介绍上一期介绍了如何利用PyTorch Lightning搭建并训练一个模型仅使用训练集为了保证模型可以泛化到未见过的数据上数据集通常被分为训练和测试两个集合测试集与训练集相互独立用以测试模型的泛化能力。本期通过增加验证和测试集来达到该目的同时还引入checkpoint和早停策略以得到模型最佳权重。 相关链接https://lightning.ai/docs/pytorch/stable/levels/basic_level_2.html 训练集、验证集、测试集的使用
1.添加依赖获取训练集和测试集
添加相应的依赖同时使用MNIST数据集获取训练和测试集
import torch.utils.data as data
from torchvision import datasets
import torchvision.transforms as transforms
from torch.utils.data import DataLoader# 加载数据测试集trainFalse
transform transforms.ToTensor()
train_set datasets.MNIST(rootMNIST, downloadTrue, trainTrue, transformtransform)
test_set datasets.MNIST(rootMNIST, downloadTrue, trainFalse, transformtransform)2.实现并调用test_step
在定义LightningModule中实现test_step方法在外部调用test方法
class LitAutoEncoder(pl.LightningModule):def training_step(self, batch, batch_idx):...def test_step(self, batch, batch_idx): # 测试该方法与training_step相似x, y batchx x.view(x.size(0), -1)z self.encoder(x)x_hat self.decoder(z)test_loss F.mse_loss(x_hat, x)self.log(test_loss, test_loss)# 初始化Trainer
trainer Trainer()# 执行test方法
trainer.test(model, dataloadersDataLoader(test_set))3.实现并调用验证集
通常使用torch.utils.data中的方法将训练集中的一部分数据化为验证集
# 训练集中的20%数据划为验证集
train_set_size int(len(train_set) * 0.8)
valid_set_size len(train_set) - train_set_size# 拆分使用data.random_split方法
seed torch.Generator().manual_seed(42)
train_set, valid_set data.random_split(train_set, [train_set_size, valid_set_size], generatorseed)与测试集一样需要在定义LightningModule中实现validation_step方法在外部调用fit方法
class LitAutoEncoder(pl.LightningModule):def training_step(self, batch, batch_idx):...def validation_step(self, batch, batch_idx):x, y batchx x.view(x.size(0), -1)z self.encoder(x)x_hat self.decoder(z)val_loss F.mse_loss(x_hat, x)self.log(val_loss, val_loss)def test_step(self, batch, batch_idx):...
# 调用torch.utils.data中的DataLoader对训练和测试集进行封装
train_loader DataLoader(train_set)
valid_loader DataLoader(valid_set)# 在fit方法中引入valid_loader即验证集
trainer Trainer()
trainer.fit(model, train_loader, valid_loader)checkpoint
checkpoint有两个作用一是能得到每一次epoch后的模型权重能得到最佳表现的权重二是能够在中断或停止后继续在当前checkpoint处继续训练。在Lightning中的checkpoint包含模型的整个内部状态这与普通的PyTorch不同即使在最复杂的分布式训练环境中Lightning也可以保存恢复模型所需的一切。包含以下状态
16-bit scaling factor (若使用16精度训练)Current epochGlobal stepLightningModule’s state_dictState of all optimizersState of all learning rate schedulersState of all callbacks (for stateful callbacks)State of datamodule (for stateful datamodules)The hyperparameters (init arguments) with which the model was createdThe hyperparameters (init arguments) with which the datamodule was createdState of Loops
保存与调用方法
# 保存方法可自定义default_root_dir路径若不设置路径将会自动保存
trainer Trainer(default_root_dirsome/path/)# 调用方法
model MyLightningModule.load_from_checkpoint(/path/to/checkpoint.ckpt)
model.eval() # disable randomness, dropout, etc...
y_hat model(x)
调用还可以使用torch的方法
checkpoint torch.load(checkpoint, map_locationlambda storage, loc: storage)
print(checkpoint[hyper_parameters])
# {learning_rate: the_value, another_parameter: the_other_value}也可以实现重现例如模型LitModel(in_dim32, out_dim10)
# 使用 in_dim32, out_dim10
model LitModel.load_from_checkpoint(PATH)
# 使用 in_dim128, out_dim10
model LitModel.load_from_checkpoint(PATH, in_dim128, out_dim10)Lightning和PyTorch完全兼容
checkpoint torch.load(CKPT_PATH)
encoder_weights checkpoint[encoder]
decoder_weights checkpoint[decoder]设置checkpoint不可见
trainer Trainer(enable_checkpointingFalse)如果想全部重新恢复
model LitModel()
trainer Trainer()自动恢复所有相关参数 model, epoch, step, LR schedulers, etc…
trainer.fit(model, ckpt_pathsome/path/to/my_checkpoint.ckpt)早停策略
EarlyStopping Callback
在Lightning中早停回调步骤如下
Import EarlyStopping callback. 载入EarlyStopping回调方法Log the metric you want to monitor using log() method. 加载日志方法Init the callback, and set monitor to the logged metric of your choice. 设置monitorSet the mode based on the metric needs to be monitored. 设置modePass the EarlyStopping callback to the Trainer callbacks flag. 调入EarlyStropping
from lightning.pytorch.callbacks.early_stopping import EarlyStoppingclass LitModel(LightningModule):def validation_step(self, batch, batch_idx):loss ...self.log(val_loss, loss)model LitModel()
trainer Trainer(callbacks[EarlyStopping(monitorval_loss, modemin)])
trainer.fit(model)# 也可以使用自定义的EarlyStopping策略
early_stop_callback EarlyStopping(monitorval_accuracy, min_delta0.00, patience3, verboseFalse, modemax)
trainer Trainer(callbacks[early_stop_callback])
# EarlyStopping的文档链接https://lightning.ai/docs/pytorch/stable/api/lightning.pytorch.callbacks.EarlyStopping.html#lightning.pytorch.callbacks.EarlyStopping注意
EarlyStopping默认在一次Validation后调用但是Validation可以自定义多少次epoch后进行一次验证例如check_val_every_n_epoch and val_check_interval。
完整代码
# coding:utf-8
import torch
import torch.nn as nn
import torch.utils.data as data
from torchvision import datasets
import torchvision.transforms as transforms
from torch.utils.data import DataLoader
import torch.nn.functional as F
import lightning as L# --------------------------------
# Step 1: 定义模型
# --------------------------------
class LitAutoEncoder(L.LightningModule):def __init__(self):super().__init__()self.encoder nn.Sequential(nn.Linear(28 * 28, 128), nn.ReLU(), nn.Linear(128, 3))self.decoder nn.Sequential(nn.Linear(3, 128), nn.ReLU(), nn.Linear(128, 28 * 28))def training_step(self, batch, batch_idx):x, y batchx x.view(x.size(0), -1)z self.encoder(x)x_hat self.decoder(z)loss F.mse_loss(x_hat, x)self.log(train_loss, loss)return lossdef test_step(self, batch, batch_idx): # 测试该方法与training_step相似x, y batchx x.view(x.size(0), -1)z self.encoder(x)x_hat self.decoder(z)test_loss F.mse_loss(x_hat, x)self.log(test_loss, test_loss)def validation_step(self, batch, batch_idx):x, y batchx x.view(x.size(0), -1)z self.encoder(x)x_hat self.decoder(z)val_loss F.mse_loss(x_hat, x)self.log(val_loss, val_loss)def configure_optimizers(self):optimizer torch.optim.Adam(self.parameters(), lr1e-3)return optimizerdef forward(self, x):# forward 定义了一次 预测/推理 行为embedding self.encoder(x)return embedding
# --------------------------------
# Step 2: 加载数据模型
# --------------------------------
transform transforms.ToTensor()
train_set datasets.MNIST(rootMNIST, downloadTrue, trainTrue, transformtransform)
test_set datasets.MNIST(rootMNIST, downloadTrue, trainFalse, transformtransform)# 训练集中的20%数据划为验证集
train_set_size int(len(train_set) * 0.8)
valid_set_size len(train_set) - train_set_size# 拆分使用data.random_split方法
seed torch.Generator().manual_seed(42)
train_set, valid_set data.random_split(train_set, [train_set_size, valid_set_size], generatorseed)
train_loader DataLoader(train_set)
valid_loader DataLoader(valid_set)autoencoder LitAutoEncoder()
# --------------------------------
# Step 3: 训练验证测试
# --------------------------------
# 训练验证
trainer L.Trainer(default_root_dirsome/path/) # 这里自定义需要保存的路径
trainer.fit(autoencoder, train_loader, valid_loader)# 测试
trainer.test(autoencoder, dataloadersDataLoader(test_set))
