HI @albanD thank you for the response.
I tried your solution but I lose the full matrix, ang get only the selected vector
x[indices[0], indices[1]]

>> tensor([ 1, -2, -1])

Also, multiplying by negative numbers by 1.1 will reduce them and instead of increasing them
so  I guess I need a calculation similar to
x + x.abs() * 0.1

I just don’t know how to apply it only on the specific indices.