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https://issues.apache.org/jira/browse/FLINK-3780?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15248270#comment-15248270
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Greg Hogan commented on FLINK-3780:
-----------------------------------

The Jaccard Similarity is computed on two vertices. For a graph with {{n}} 
vertices there are {{(n choose 2)}} similarity scores which is {{O(n^2)}}. 
Also, lack of similarity (here, no shared neighbors) is usually not very 
interesting.

> Jaccard Similarity
> ------------------
>
>                 Key: FLINK-3780
>                 URL: https://issues.apache.org/jira/browse/FLINK-3780
>             Project: Flink
>          Issue Type: New Feature
>          Components: Gelly
>    Affects Versions: 1.1.0
>            Reporter: Greg Hogan
>            Assignee: Greg Hogan
>
> Implement a Jaccard Similarity algorithm computing all non-zero similarity 
> scores. This algorithm is similar to {{TriangleListing}} but instead of 
> joining two-paths against an edge list we count two-paths.
> {{flink-gelly-examples}} currently has {{JaccardSimilarityMeasure}} which 
> relies on {{Graph.getTriplets()}} so only computes similarity scores for 
> neighbors but not neighbors-of-neighbors.
> This algorithm is easily modified for other similarity scores such as 
> Adamic-Adar similarity where the sum of endpoint degrees is replaced by the 
> degree of the middle vertex.



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