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https://issues.apache.org/jira/browse/FELIX-2528?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Karl Pauls updated FELIX-2528:
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Fix Version/s: framework-3.0.2
(was: framework-3.2.0)
> Potential performance issue in resolver when uses constraint conflict is
> detected
> ---------------------------------------------------------------------------------
>
> Key: FELIX-2528
> URL: https://issues.apache.org/jira/browse/FELIX-2528
> Project: Felix
> Issue Type: Improvement
> Components: Framework
> Affects Versions: framework-3.0.0, framework-3.0.1
> Reporter: Richard S. Hall
> Assignee: Richard S. Hall
> Fix For: framework-3.0.2
>
>
> Whenever the resolver detects a uses constraint conflict, it tries to create
> two permutations of its solution search space. Since a conflict effectively
> arises between two parties (an existing package constraint and a package
> constraint being added), the algorithm creates a potential solution
> permutation removing the opposite party from each, since it doesn't know
> which one may ultimately lead to a correct solution. The permutation removing
> the added package constraint candidates is called a "uses" permutation (since
> it permutates the package being used) while the permutation removing the
> existing package constraint is called an "import" permutation (since it
> generally is causing a backtrack on a previously selected imported package).
> The algorithm is basically depth-first search, which ultimately results in it
> giving priority to the "uses" permutations. This means it won't backtrack on
> any choices for imports until it determines that a previous choice was
> incorrect. This appears to work fairly well in practice. The downside is that
> it is possible that we keep detecting conflicts related to an incorrect
> import decision before determining that the original import decision was
> incorrect. This results in lots of import permutations being generated that
> are effectively smaller and smaller subsets of each other. This can consume a
> lot of memory which slows things down as well as creates lots of largely
> repetitive permutations to process.
> In short, we need to try to detect if we've already permutated an import and
> not do it again.
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