https://www.chenk.top/en/tags/self-supervised/Recent content in Self-Supervised on Chen Kai BlogHugoenWed, 31 Dec 2025 09:00:00 +0000https://www.chenk.top/en/recommendation-systems/11-contrastive-learning/Wed, 31 Dec 2025 09:00:00 +0000https://www.chenk.top/en/recommendation-systems/11-contrastive-learning/<p>Classical recommenders learn from one signal: did a user click, watch, or buy? That signal is precious, but it is also brutally sparse. Most users touch fewer than 1% of the catalogue, most items are touched by fewer than 0.1% of users, and a brand-new item or user has nothing at all. Optimising a model directly against such sparse labels almost guarantees overfitting on the head and silence on the tail.</p>