一般而言,神经网络的喂入数据集很大,不会在一次迭代中全部使用,那样会撑死的。
一般,在一次迭代中分批喂给部分数据,用小部分数据分批训练要比用全部数据训练的结果要好。
pytorch中提供此类批训练功能,DataLoader
难点:
import torch.utils.data as Data
torch_dataset = Data.TensorDataset(x, y)
loader = Data.DataLoader(
dataset=torch_dataset, # torch TensorDataset format
batch_size==BATCH_SIZE, # mini batch size
shuffle=True, # random shuffle for training
num_workers=2 # subprocesses for loading data
)
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
DataLoader 是 torch 给你用来包装你的数据的工具. 所以你要讲自己的 (numpy array 或其他) 数据形式装换成 Tensor, 然后再放进这个包装器中. 使用 DataLoader 有什么好处呢? 就是他们帮你有效地迭代数据, 举例:
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(x, 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.]
"""
注意:使用DataLoader必须要用main函数
if __name__ == '__main__':
"""
View more, visit my tutorial page: https://morvanzhou.github.io/tutorials/
My Youtube Channel: https://www.youtube.com/user/MorvanZhou
Dependencies:
torch: 0.1.11
"""
import torch
import torch.utils.data as Data
torch.manual_seed(1) # reproducible
BATCH_SIZE = 5
# BATCH_SIZE = 8
x = torch.linspace(1, 10, 10) # this is x data (torch tensor)
y = torch.linspace(10, 1, 10) # this is y data (torch tensor)
torch_dataset = Data.TensorDataset(x, y)
loader = Data.DataLoader(
dataset=torch_dataset, # torch TensorDataset format
batch_size=BATCH_SIZE, # mini batch size
shuffle=True, # random shuffle for training
num_workers=2, # subprocesses for loading data
)
def show_batch():
for epoch in range(3): # train entire dataset 3 times
for step, (batch_x, batch_y) in enumerate(loader): # for each training step
# train your data...
print('Epoch: ', epoch, '| Step: ', step, '| batch x: ',
batch_x.numpy(), '| batch y: ', batch_y.numpy())
if __name__ == '__main__':
show_batch()