Let

x = tensor([[[[0, 1, 1, 1],

[1, 1, 1, 1],

[1, 1, 1, 1],

[1, 1, 1, 1]]]])

if we do x.nonzero() we get

x.nonzero() = tensor([[

[0, 0, 0, 1],

[0, 0, 0, 2],

[0, 0, 0, 3],

[0, 0, 1, 0],

[0, 0, 1, 1],

[0, 0, 1, 2],

[0, 0, 1, 3],

[0, 0, 2, 0],

[0, 0, 2, 1],

[0, 0, 2, 2],

[0, 0, 2, 3],

[0, 0, 3, 0],

[0, 0, 3, 1],

[0, 0, 3, 2],

[0, 0, 3, 3]])

It is possible to have a 1-D Array where we return the number of the index of x :

tensor([[[[ 1,2,3],[4,5,6,7],

[ 8,9,10,11],[12,13,14,15]]])