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Jim Ferenczi commented on LUCENE-8759: -------------------------------------- I tried this approach but the shift for denormalized numbers is computed from the float bits so I started from the same bits for normalized numbers too. > BlockMaxConjunctionScorer's simplified way of computing max scores hurts > performance > ------------------------------------------------------------------------------------ > > Key: LUCENE-8759 > URL: https://issues.apache.org/jira/browse/LUCENE-8759 > Project: Lucene - Core > Issue Type: Improvement > Reporter: Adrien Grand > Priority: Minor > Attachments: LUCENE-8759.patch > > > BlockMaxConjunctionScorer computes the minimum value that the score should > have after each scorer in order to be able to interrupt scorer as soon as > possible. For instance say scorers A, B and C produce maximum scores that are > equal to 4, 2 and 1. If the minimum competitive score is X, then the score > after scoring A, B and C must be at least X, the score after scoring A and B > must be at least X-1 and the score after scoring A must be at least X-1-2. > However this is made a bit more complex than that due to floating-point > numbers and the fact that intermediate score values are doubles which only > get casted to a float after all values have been summed up. In order to keep > things simple, BlockMaxConjunctionScore has the following comment and code > {code} > // Also compute the minimum required scores for a hit to be > competitive > // A double that is less than 'score' might still be converted to > 'score' > // when casted to a float, so we go to the previous float to avoid > this issue > minScores[minScores.length - 1] = minScore > 0 ? > Math.nextDown(minScore) : 0; > {code} > It simplifies the problem by calling Math.nextDown(minScore). However this is > problematic because it defeats the fact that TopScoreDocCollector calls > setMinCompetitiveScore on the float value that is immediately greater than > the k-th greatest hit so far. > nextDown(minScore) is not the value that we need. The value that we need is > the smallest double that converts to minScore when casted to a float, which > would be half-way between nextDown(minScore) and minScore. In some cases this > would help get better performance out of conjunctions, especially if some > clauses produce constant scores. > MaxScoreSumPropagator#setMinCompetitiveScore has the same issue. -- This message was sent by Atlassian JIRA (v7.6.3#76005) --------------------------------------------------------------------- To unsubscribe, e-mail: dev-unsubscr...@lucene.apache.org For additional commands, e-mail: dev-h...@lucene.apache.org