SimHash and MinHash compress high-dimensional document features into compact signatures that preserve similarity, letting search engines detect near-duplicates at web scale in sub-linear time.
GSP and PrefixSpan both find ordered behavior that appears often enough in a database of sequences. GSP generates candidate patterns and counts them; PrefixSpan projects the database to the suffixes after a prefix and grows patterns inside those smaller databases.
Three algorithms split a graph into communities using only local moves, with no preset number of groups. Search systems use them: one in a web-ranking patent, another in language-model retrieval.