Before revision:  Together, RecOpt and RecDex outperform state-of-the-art indexes by 3.2\times on average, and up to 10.9\times, on widely studied models for recommendations and MIPS .
After revision:  Together, RecOpt and RecDex outperform state-of-the-art indexes by 3.2\times on average, and up to 10.9\times, on widely studied MIPS datasets .