Apple's CoGR Co-Evolves Query and Item Generators with RL, Boosts Retrieval F1 by Up to 36.1%

antoine_chaffin · x · 2026-09-06

Apple researchers propose CoGR (arXiv:2609.00638), a generative retrieval framework that trains LLM keyword generators for both the query and item sides instead of only augmenting queries. A two-stage pipeline — SFT to align the keyword space, then alternating GRPO-based RL — co-evolves both sides against each other's frozen inverted index, with the item side rewarded via counterfactual marginal retrieval-F1 gains. Keywords match through a standard inverted index, preserving existing keyword infrastructure. Across 10 sparse, dense, and generative baselines, CoGR achieves the best results, with +10.9% / +36.1% F1 over the strongest baselines on an internal App Store marketplace dataset.

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