u = F.pad(r, (0, lookahead_delta - 1)).as_strided(
(r.size(0), r.size(1), lookahead_delta),
(r.size(1) + lookahead_delta - 1, 1, 1),
)
u = F.pad(r, (0, lookahead_delta - 1)).as_strided(
(r.size(0), r.size(1), lookahead_delta),
(r.size(1) + lookahead_delta - 1, 1, 1),
)