PyTorch05-批训练(Batch Training)

原文：批训练 - PyTorch 莫烦Python (mofanpy.com)

单个数据训练太慢，一批一批训练会加快训练速度

DataLoader

Torch提供了DataLoader来帮助批训练

import torch
import torch.utils.data as Data
torch.manual_seed(1)    # reproducible

BATCH_SIZE = 5      # 批训练的数据个数

x = torch.linspace(1, 10, 10)       # x data (torch tensor)
y = torch.linspace(10, 1, 10)       # y data (torch tensor)

# 先转换成 torch 能识别的 Dataset
torch_dataset = Data.TensorDataset(data_tensor=x, target_tensor=y)

# 把 dataset 放入 DataLoader
loader = Data.DataLoader(
    dataset=torch_dataset,      # torch TensorDataset format
    batch_size=BATCH_SIZE,      # mini batch size
    shuffle=True,               # 要不要打乱数据 (打乱比较好)
    num_workers=2,              # 多线程来读数据
)

for epoch in range(3):   # 训练所有!整套!数据 3 次
    for step, (batch_x, batch_y) in enumerate(loader):  # 每一步 loader 释放一小批数据用来学习
        # 假设这里就是你训练的地方...

        # 打出来一些数据
        print('Epoch: ', epoch, ' Step: ', step, ' batch x: ',
              batch_x.numpy(), ' batch y: ', batch_y.numpy())

"""
Epoch:  0  Step:  0  batch x:  [ 6.  7.  2.  3.  1.]  batch y:  [  5.   4.   9.   8.  10.]
Epoch:  0  Step:  1  batch x:  [  9.  10.   4.   8.   5.]  batch y:  [ 2.  1.  7.  3.  6.]
Epoch:  1  Step:  0  batch x:  [  3.   4.   2.   9.  10.]  batch y:  [ 8.  7.  9.  2.  1.]
Epoch:  1  Step:  1  batch x:  [ 1.  7.  8.  5.  6.]  batch y:  [ 10.   4.   3.   6.   5.]
Epoch:  2  Step:  0  batch x:  [ 3.  9.  2.  6.  7.]  batch y:  [ 8.  2.  9.  5.  4.]
Epoch:  2  Step:  1  batch x:  [ 10.   4.   8.   1.   5.]  batch y:  [  1.   7.   3.  10.   6.]
"""