advantage = teacher_logprob - student_logprob — following
“Reinforcement Learning via Self-Distillation”
(Hübotter et al., 2026): “the current model conditioned on feedback as a
self-teacher… without any external teacher or explicit reward model.”
Distinct from the unrelated, same-acronym “sDPO: Don’t Use Your Data All at Once” — sequential preference-data
subsetting for offline DPO, not self-distillation.
rl_datum and forward_backward_payload are the shared datum helpers.