Pytorch 得到 RuntimeError: Found dtype Double 但预期 Float

Question

我正在尝试在 PyTorch 中实现神经网络，但它似乎不起作用。问题似乎出在训练循环中。我已经花了几个小时来解决这个问题，但无法做到正确。请帮忙，谢谢。

我没有添加数据预处理部分。

# importing libraries
import pandas as pd
import numpy as np
import torch
import torch.nn as nn
from torch.utils.data import Dataset
from torch.utils.data import DataLoader
import torch.nn.functional as F

# get x function (dataset related stuff)
def Getx(idx):
    sample = samples[idx]
    vector = Calculating_bottom(sample)
    vector = torch.as_tensor(vector, dtype = torch.float64)
    
    return vector

# get y function (dataset related stuff)
def Gety(idx):
    y = np.array(train.iloc[idx, 4], dtype = np.float64)
    y = torch.as_tensor(y, dtype = torch.float64)
    
    return y

# dataset
class mydataset(Dataset):

    def __init__(self):
        super().__init__()

    def __getitem__(self, index):
        x = Getx(index)
        y = Gety(index)
        
        return x, y

    def __len__(self):
        return len(train)
    
dataset = mydataset()

# sample dataset value
print(dataset.__getitem__(0))

(张量([ 5., 5., 8., 14.], dtype=torch.float64), tensor(-0.3403, dtype=torch.float64))

# data-loader
dataloader = DataLoader(dataset, batch_size = 1, shuffle = True)

# nn architecture
class Net(nn.Module):
    def __init__(self):
        super().__init__()
        self.fc1 = nn.Linear(4, 4)
        self.fc2 = nn.Linear(4, 2)
        self.fc3 = nn.Linear(2, 1)

    def forward(self, x):
        x = x.float()
        x = F.relu(self.fc1(x))
        x = F.relu(self.fc2(x))
        x = self.fc3(x)
        return x

model = Net()

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

# hyper-parameters
criterion = nn.MSELoss()
optimizer = torch.optim.SGD(model.parameters(), lr=0.001)

# training loop

for epoch in range(5):
    
    for batch in dataloader:
        
        # unpacking
        x, y = batch
        x.to(device)
        y.to(device)
        
        # reset gradients
        optimizer.zero_grad()
        
        # forward propagation through the network
        out = model(x)
        
        # calculate the loss
        loss = criterion(out, y)
        
        # backpropagation
        loss.backward()
        
        # update the parameters
        optimizer.step()

错误：

/opt/conda/lib/python3.7/site-packages/torch/nn/modules/loss.py:446: UserWarning: Using a target size (torch.Size([1])) that is different to the input size (torch.Size([1, 1])). This will likely lead to incorrect results due to broadcasting. Please ensure they have the same size.
  return F.mse_loss(input, target, reduction=self.reduction)
---------------------------------------------------------------------------
RuntimeError                              Traceback (most recent call last)
<ipython-input-18-3f68fcee9ff3> in <module>
     20 
     21         # backpropagation
---> 22         loss.backward()
     23 
     24         # update the parameters

/opt/conda/lib/python3.7/site-packages/torch/tensor.py in backward(self, gradient, retain_graph, create_graph)
    219                 retain_graph=retain_graph,
    220                 create_graph=create_graph)
--> 221         torch.autograd.backward(self, gradient, retain_graph, create_graph)
    222 
    223     def register_hook(self, hook):

/opt/conda/lib/python3.7/site-packages/torch/autograd/__init__.py in backward(tensors, grad_tensors, retain_graph, create_graph, grad_variables)
    130     Variable._execution_engine.run_backward(
    131         tensors, grad_tensors_, retain_graph, create_graph,
--> 132         allow_unreachable=True)  # allow_unreachable flag
    133 
    134 

RuntimeError: Found dtype Double but expected Float

Answer 1

您需要数据的数据类型与模型的数据类型相匹配。

将模型转换为双精度（推荐用于没有严重性能问题的简单网络，例如您的）

# nn architecture
class Net(nn.Module):
    def __init__(self):
        super().__init__()
        self.fc1 = nn.Linear(4, 4)
        self.fc2 = nn.Linear(4, 2)
        self.fc3 = nn.Linear(2, 1)
        self.double()

或将数据转换为浮点数。

class mydataset(Dataset):

    def __init__(self):
        super().__init__()

    def __getitem__(self, index):
        x = Getx(index)
        y = Gety(index)
        
        return x.float(), y.float()

Answer 2

检查“out”和“y”的数据类型

print(out.dtype)
print(y.dtype)

您可能会发现不同之处

"torch.float32"
"torch.float64"

将它们设置为相同的类型。