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https://issues.apache.org/jira/browse/GIRAPH-266?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13421580#comment-13421580
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Gianmarco De Francisci Morales commented on GIRAPH-266:
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Average is not an associative operation, so I would not support it directly in
aggregators.
So I am also in favor of option 1.
Option 3 sounds over-engineered to me, however there might be use cases where
one wants to aggregate complex values, so it might have some value in the long
run.
> Average aggregators don't calculate real average
> ------------------------------------------------
>
> Key: GIRAPH-266
> URL: https://issues.apache.org/jira/browse/GIRAPH-266
> Project: Giraph
> Issue Type: Bug
> Reporter: Maja Kabiljo
> Assignee: Maja Kabiljo
>
> Average aggregators calculate average on workers, and then workers' averages
> are sent to the master, where we actually calculate the average of averages.
> For example, if one worker aggregates value 2, the other values 4 and 6, and
> third values 8, 8 and 8, we'll get the result of 5 instead of 6.
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