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From Adrien Grand <jpou...@gmail.com>
Subject Re: Impact and WAND
Date Wed, 10 Jul 2019 14:52:20 GMT
To clarify, the scoring process is not accelerated because we
terminate early but because we can skip low-scoring matches (there
might be competitive hits at the very end of the index).

CompetitiveImpactAccumulator is indeed related to WAND. It helps store
the maximum score impacts per block of documents in postings lists.
Then this information is leveraged by block-max WAND in order to skip
low-scoring blocks.

This does indeed help avoid reading norms, but also document IDs and
term frequencies.

On Wed, Jul 10, 2019 at 4:10 PM Wu,Yunfeng <wuyunfeng01@baidu.com> wrote:
>
> Hi,
>
>  We discuss some topic from https://github.com/apache/lucene-solr/pull/595. As Atri Sharma
propose discuss with the java dev list.
>
>
>  Impact `frequency ` and `norm ` just to accelerate the `score process`  which  `terminate
early`.
>
> In impact mode, `CompetitiveImpactAccumulator` will record (freq, norm) pair , would
stored at index level. Also I noted `CompetitiveImpactAccumulator` commented with `This class
accumulates the (freq, norm) pairs that may produce competitive scores`,  maybe related to
`WAND`?
>
>
> The norm value which produced or consumed by `Lucene80NormsFormat`.
>
> In this ` Impact way`, we can avoid read norms from `Lucene80NormsProducer` that may
generate the extra IO?  ( the norm value Lucene stored twice.)and take full advantage
of the WAND method?



-- 
Adrien

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