Josh Devins 68ba571f70
Adds recall@k metric to rank eval API (#52889)
This change adds the recall@k metric and refactors precision@k to match
the new metric.

Recall@k is an important metric to use for learning to rank (LTR)
use-cases. Candidate generation or first ranking phase ranking functions
are often optimized for high recall, in order to generate as many
relevant candidates in the top-k as possible for a second phase of
ranking. Adding this metric allows tuning that base query for LTR.

See: https://github.com/elastic/elasticsearch/issues/51676
Backports: https://github.com/elastic/elasticsearch/pull/52577
2020-02-27 16:04:24 +01:00
..
2020-02-20 14:39:44 +00:00