PyTorch学习问题记录

Q1:def train() 中的model.train()的作用是什么?为什么要写?

A1:class torch.nn.Module中 train(mode=True)

  Sets the module in training mode. This has any effect only on modules such as Dropout or BatchNorm.

  参看 http://pytorch.org/docs/master/nn.html

 

Q2:torch.gather()函数的功能是什么?

 1 t = torch.Tensor([[1, 2], [3, 4]])
 2 print(t)
 3 a = torch.gather(t, 1, torch.LongTensor([[0,0], [1,0]]))
 4 print(a)
 5 '''
 6  1  2
 7  3  4
 8 [torch.FloatTensor of size 2x2]
 9 
10  1  1
11  4  3
12 [torch.FloatTensor of size 2x2]
13 '''

A2:

out[i][j][k] = input[index[i][j][k]][j][k]    # if dim == 0
out[i][j][k] = input[i][index[i][j][k]][k]    # if dim == 1
out[i][j][k] = input[i][j][index[i][j][k]]    # if dim == 2

out[i][j] = input[index[i][j]][j]
out[i][j] = input[i][index[i][j]]

out[0][0] = input[0][index[0][0]] = input[0][0] = 1
out[0][1] = input[0][index[0][1]] = input[0][0] = 1
out[1][0] = input[1][index[1][0]] = input[1][1] = 4

out[1][1] = input[1][index[1][1]] = input[1][0] = 3

 

Q3:torch.norm() 函数的功能是什么?

 1 a = torch.FloatTensor([[1, 2], [3, 4]])
 2 b = torch.norm(a)
 3 print(a)
 4 print(b)
 5 '''
 6  1  2
 7  3  4
 8 [torch.FloatTensor of size 2x2]
 9 
10 5.477225575051661
11 '''

 A3:

norm() 函数是求范数,一般默认是2范数。平方和开根号。

参考博文:几种范数的简单介绍

normal() 函数是求正太分布。

 

Q4: topk()函数

1 topi = torch.LongTensor([5])        # [torch.LongTensor of size 1]
2 topii = torch.LongTensor([[5]])     # [torch.LongTensor of size 1x1]
3 ni = topi[0]
4 nii = topii[0][0]
5 print(ni, nii)                           # 5 5

 

Q5:

1 loss = Variable(torch.FloatTensor([1]))
2 print(loss.data)                      # 1 [torch.FloatTensor of size 1]
3 print(loss.data[0])                   # 1.0  

 

posted @ 2017-07-28 19:14  Joyce_song94  阅读(2445)  评论(0编辑  收藏  举报