“…Meanwhile, as the new features and old features are interchangeable with each other, the gallery images can be backfilled on-the-fly, and the retrieval performances would be gradually improved to approach the optimal accuracy of the new model, dubbed as hot-refresh model upgrades (see Figure 1 (a)). Although existing compatible training methods (Meng et al, 2021;Shen et al, 2020) make it possible to upgrade the model in a hot-refresh manner, they still face the challenge of model regression (Yan et al, 2020;Li & Hoiem, 2018), which is actually caused by negative flips, i.e., queries correctly indexed by the old model are incorrectly recognized by the new model (see Figure 1 (b)). We claimed that, during the procedure of hot-refresh model upgrades, the negative flips occur when the new-to-new similarities between negative query-gallery pairs are larger than the new-to-old similarities between compatible positive query-gallery pairs.…”