def round_core(core, mode, rank):
new_dims = [mode] + [m for m in range(core.ndim) if m != mode]
mode_dim = core.shape[mode]
flat_core = core.transpose(new_dims).reshape((mode_dim, -1), order='F')
u, s, vt = np.linalg.svd(flat_core, full_matrices=False)
rfactor = u[:, :rank]
new_core = (np.ascontiguousarray(
s[:rank, np.newaxis] * vt[:rank, :]).reshape(
rank, *[core.shape[i] for i in new_dims[1:]],
order='F').transpose(inverse_permutation(np.array(new_dims))))
return rfactor, new_core
def return_order(a):
return np.take(range(1,
len(a) + 1), inverse_permutation(np.argsort(a)))