1.torch.repeat和tf.tile
两个函数都是将tensor的某一维度进行制定次数的重复：

a_ = torch.repeat(a, [x,y,x]) #a是三维tensor，将其1，2，3维分别repeat x, y, z次
b_ = tf.tile(b, [c,d,e,f]) #b是三维tensor，将其1，2，3，4维分别repeat a，b，c，d次

2.torch.diagonal和tf.diag_part
提取张量的主对角线元素

#torch
x = torch.randn(4,4)
tensor([[ 8.4527e-01,  1.9236e+00, -6.9886e-01, -4.1077e-01],
        [-1.4905e+00,  2.8126e-01,  9.9094e-02, -2.0024e-03],
        [-6.0617e-01,  1.0577e+00, -7.8548e-01,  2.0802e+00],
        [-7.9660e-01,  1.2871e+00, -3.5069e-01, -1.5513e+00]])

torch.diagonal(x)
# tensor([ 0.8453,  0.2813, -0.7855, -1.5513])

#tensorflow
a = tf.diag_part(b)

#待续