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From "ASF subversion and git services (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (LUCENE-7942) For Geo3d paths, aggregating distance values using "+" is not adequate for squared distances
Date Tue, 29 Aug 2017 05:17:00 GMT

    [ https://issues.apache.org/jira/browse/LUCENE-7942?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16144753#comment-16144753
] 

ASF subversion and git services commented on LUCENE-7942:
---------------------------------------------------------

Commit c01d692baca08a7929055a4d41ad2aae7b50661d in lucene-solr's branch refs/heads/master
from [~kwright@metacarta.com]
[ https://git-wip-us.apache.org/repos/asf?p=lucene-solr.git;h=c01d692 ]

LUCENE-7942: Explicitly require conversion to 'aggregation' form before aggregating distances,
plus require a conversion back.  This is more efficient than my initial commit for this ticket,
since sqrt values will be cached for path segments, and will not need to be recomputed.


> For Geo3d paths, aggregating distance values using "+" is not adequate for squared distances
> --------------------------------------------------------------------------------------------
>
>                 Key: LUCENE-7942
>                 URL: https://issues.apache.org/jira/browse/LUCENE-7942
>             Project: Lucene - Core
>          Issue Type: Bug
>          Components: modules/spatial3d
>            Reporter: Karl Wright
>            Assignee: Karl Wright
>             Fix For: 6.7, master (8.0), 7.1
>
>
> The GeoStandardPath object aggregates distances segment by segment using simple addition.
 For some kinds of Distance computations, though, addition is not an adequate way to do this.
 The xxxSquaredDistance computations, for example, do not produce true squared distances but
rather a distance metric that is a combination of both squared and linear.
> I propose adding support in Distance for aggregation, which would allow distance calculators
to compute an accurate distance (at some computational cost) instead.



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