[LUCENE-9071] Speed up computation of BM25 scores

• Type: Improvement
• Status: Closed
• Priority: Minor
• Resolution: Fixed
• Fix Version/s: 8.4
• Lucene Fields: New
• Assignee: Unassigned
• Reporter: Adrien Grand
• Created: 28/Nov/19 09:18
• Updated: 28/Aug/22 15:53
• Resolved: 09/Dec/19 18:50

Description

We changed the way BM25 scores are computed in LUCENE-7997 in order to guarantee monotonicity of scores, but this translated to a small decrease of throughput, see annotation CC (October 2017) on Mike's nightly benchmarks. Even though the total number of score computations has decreased since we introduced block-max WAND, its relative cost is not negligible since we not only compute scores on collected documents, but also when decoding skip lists in order to compute the maximum score per block, or group of blocks.

Issue Links

• links to: GitHub Pull Request #1043