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From Sean Owen <>
Subject Re: deadlock in FastByIDMap.find() ?
Date Sat, 05 Dec 2009 09:31:01 GMT
That all sounds fine, should be no problem with this usage pattern. I
don't think the issue is where you think it is -- The problem seemed
to be with the FastMap used to cache recommendations. Is there
anything interesting about how this is used? I just added a couple
unit tests for the cache to try to reproduce it but didn't see

You can remove CachingRecommender to see what happens but that would
be a shame since it's just avoiding the problem. If there's an issue
I'm keen to track it down.

I can't figure out what the issue is. Maybe I can add some asserts to
the code that could trigger some signs of a problem.

2009/12/5 施伟伟 <>:
> Thanks for reply.
> It does not happen all the time. I saw this twice and could not easily
> reproduce it.
> Next time I will try testing it with jpda enabled.
> I am not sure if I am doing something wrong in the data model.
> First I fill the FastMap with data read from external data source.
> Then I iterate all entries in FastMap and find a set of items that I don't
> need.
> Finally I iterate the entries again to remove those items from FastMap. If
> the item set of any userID becomes empty, the userID will be removed from
> FastMap too.
> Maybe I should do these outside mahout using ordinary Map?
> Thanks,
> Weiwei

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