Pytorch Tensor的统计属性实例讲解

import torch
 
a = torch.full([8], 1)
b = a.reshape([2, 4])
c = a.reshape([2, 2, 2])
 
# 求L1范数(所有元素绝对值求和)
print(a.norm(1), b.norm(1), c.norm(1))
# 求L2范数(所有元素的平方和再开根号)
print(a.norm(2), b.norm(2), c.norm(2))
 
# 在b的1号维度上求L1范数
print(b.norm(1, dim=1))
# 在b的1号维度上求L2范数
print(b.norm(2, dim=1))
 
# 在c的0号维度上求L1范数
print(c.norm(1, dim=0))
# 在c的0号维度上求L2范数
print(c.norm(2, dim=0))

tensor(8.) tensor(8.) tensor(8.)
tensor(2.8284) tensor(2.8284) tensor(2.8284)
tensor([4., 4.])
tensor([2., 2.])
tensor([[2., 2.],
  [2., 2.]])
tensor([[1.4142, 1.4142],
  [1.4142, 1.4142]])

b = torch.arange(8).reshape(2, 4).float()
print(b)
# 均值,累加,最小,最大,累积
print(b.mean(), b.sum(), b.min(), b.max(), b.prod())
# 打平后的最小最大值索引
print(b.argmax(), b.argmin())

tensor([[0., 1., 2., 3.],
  [4., 5., 6., 7.]])
tensor(3.5000) tensor(28.) tensor(0.) tensor(7.) tensor(0.)
tensor(7) tensor(0)

a = torch.rand(4, 10)
print(a)
# 在第二维度上求最大值索引
print(a.argmax(dim=1))

tensor([[0.0711, 0.5641, 0.7945, 0.6964, 0.3609, 0.5817, 0.1705, 0.6913, 0.1263,
   0.8346],
  [0.0810, 0.0771, 0.1983, 0.0344, 0.1067, 0.9591, 0.8515, 0.3046, 0.0491,
   0.1291],
  [0.3527, 0.2676, 0.9859, 0.2656, 0.1985, 0.3759, 0.8221, 0.3571, 0.5340,
   0.7759],
  [0.0969, 0.3954, 0.5478, 0.3543, 0.8253, 0.9291, 0.4960, 0.4390, 0.3780,
   0.5858]])
tensor([9, 5, 2, 5])

print(c.max(dim=1))

print(c.argmax(dim=1, keepdim=True))
print(c.max(dim=1, keepdim=True))

tensor([[2],
  [2],
  [5],
  [7]])
(tensor([[0.9589],
  [1.7394],
  [1.3448],
  [2.2079]]), tensor([[2],
  [2],
  [5],
  [7]]))

# 2个样本,分为10个类别的置信度
d = torch.randn(2, 10) 
# 最大概率的3个类别
print(d.topk(3, dim=1)) 
# 最小概率的3个类别
print(d.topk(3, dim=1, largest=False)) 
# 求第8小概率的类别(一共10个那就是第3大)
print(d.kthvalue(8, dim=1)) 

(tensor([[2.0692, 1.6490, 0.9526],
  [1.5983, 1.5737, 1.5532]]), tensor([[6, 3, 5],
  [8, 1, 2]]))
(tensor([[-1.0023, -0.6423, 0.0655],
  [-1.2959, -1.1504, -0.9859]]), tensor([[4, 0, 2],
  [0, 5, 3]]))
(tensor([0.9526, 1.5532]), tensor([5, 2]))

import torch
 
a = torch.randn(2, 3)
b = torch.randn(2, 3)
print(a)
print(b)
# 比较是否大于0，是对应位置返回1，否对应位置返回0，注意得到的是ByteTensor
print(a > 0) 
print(torch.gt(a, 0))
# 是否不等于0，是对应位置返回1，否对应位置返回0
print(a != 0)
# 比较每个位置是否相等，是对应位置返回1，否对应位置返回0
print(torch.eq(a, b)) 
# 比较每个位置是否相等，全部相等时才返回True
print(torch.equal(a, b), torch.equal(a, a)) 

tensor([[-0.1425, -1.1142, 0.2224],
  [ 0.6142, 1.7455, -1.1776]])
tensor([[-0.0774, -1.1012, -0.4862],
  [-0.3110, -0.2110, 0.0381]])
tensor([[0, 0, 1],
  [1, 1, 0]], dtype=torch.uint8)
tensor([[0, 0, 1],
  [1, 1, 0]], dtype=torch.uint8)
tensor([[1, 1, 1],
  [1, 1, 1]], dtype=torch.uint8)
tensor([[0, 0, 0],
  [0, 0, 0]], dtype=torch.uint8)
False True