IsotropicTVRegulariser in parameter.py is incorrect due to typo

[idc9]

line 86 of IsotropicTVRegulariser's _regulariser_2d function in parameter.py is missing a :

It currently reads

(parameter[:, 1:, 1:] - parameter[:, -1, 1:]).pow(2)*self._scaling[0]

when it should read

(parameter[:, 1:, 1:] - parameter[:, :-1, 1:]).pow(2)*self._scaling[0]

The same typo appears in line 94 of _regulariser_3d. Note this is implemented correctly in the displacement regularizer class (e.g. see line 58).

Test case

You can check this using the following simple test case and the formula on page 3 from this paper where the answer should be 2 * sqrt(10)

X = np.array([[0, 1, 2], [3, 4, 5]])
T = torch.from_numpy(X).unsqueeze(0).float()

def current_incorrect(T):
    dx = (T[:, 1:, 1:] - T[:, -1, 1:]).pow(2)
    dy = (T[:, 1:, 1:] - T[:, 1:, :-1]).pow(2)
    return torch.sqrt(dx + dy).sum()

def correct_isotropic_TV(T):
    dx = (T[:, 1:, 1:] - T[:, :-1, 1:]).pow(2)
    dy = (T[:, 1:, 1:] - T[:, 1:, :-1]).pow(2)
    return torch.sqrt(dx + dy).sum()

np.allclose(current_incorrect(T).data.numpy(), 2*np.sqrt(10))
False

np.allclose(correct_isotropic_TV(T).data.numpy(), 2*np.sqrt(10))
True

[RobinSandkuehler]

Thank you very much. We fixed it.