atris commented on issue #854: Shared PQ Based Early Termination for Concurrent 
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URL: https://github.com/apache/lucene-solr/pull/854#issuecomment-530509226
 
 
   > I think we're talking of different approaches, hence the confusion. It is 
correct that we can start setting the minimum score when the global count of 
document that we collected reaches the requested size but if the local pqs are 
not full you can only use the minimum minimum score.
   > So the bottom score of the minimum scores.
   > Requiring a queue to be filled completely before publishing a minimum 
score allows to use the maximum minimum score among the slices that have a full 
pq. We can mix the two approaches, switching from the minimum minimum to the 
maximum minimum when pqs are filled but I wonder if this is really needed since 
topN is a small value ? Said differently I wonder if checking the global 
minimum score before a single pq is filled is a premature optimization ?
   
   I see your point. So, what you are proposing is that we basically allow only 
the PQs that are full to publish the minimum score, and if there are multiple 
full PQs publishing, take the maximum of all bottom scores as the global 
minimum?
   
   Sounds like a fair approach -- I can post a patch to start with.
   
   My only concern being (as you rightly captured) is the case when in Top N, N 
is significant. In that scenario, we might be sub optimal here. But, 
nevertheless, this approach will satisfy a large number of usecases.
   
   RE: synchronization, what are your thoughts on using a global shared array 
where each collector publishes its bottom value vs message passing?

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