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https://issues.apache.org/jira/browse/GROOVY-4606?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16299379#comment-16299379
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Jochen Theodorou commented on GROOVY-4606:
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The problem with the HashMap idea is, that it works only if equals and hashcode
are defined accordingly. That is not the case in general. For example for
double 0 and BigDecimal 0 being equal in the Groovy sense, but not for a
HashMap.
I guess a better solution would be to have a second, faster unique method, that
does not take coercing into account.
> Exteremely bad performance of .unique() and .unique {closure}
> -------------------------------------------------------------
>
> Key: GROOVY-4606
> URL: https://issues.apache.org/jira/browse/GROOVY-4606
> Project: Groovy
> Issue Type: Bug
> Components: groovy-jdk
> Affects Versions: 1.7.5
> Reporter: Maxym Mykhalchuk
> Attachments: UniqueMath.java
>
>
> DefaultGroovyMethods.unique has two inner loops, so its complexity is O(n^2)
> Practically it means that it starts taking ages on collections with 1000 or
> more elements.
> Simply adding elements to a linked hash set would get O(n*log n) performance.
> Will develop my own unique implementation after New Year, and will attach it
> here
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