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From Michael McCandless <luc...@mikemccandless.com>
Subject Re: Repeatability of results
Date Mon, 02 Apr 2012 21:33:46 GMT
Hmm that's odd.

If the scores were identical I'd expect different sort order, since we
tie-break by internal docID.

But if the scores are different... the insertion order shouldn't
matter.  And, the score should not change as a function of insertion
order...

Do you have a small test case?

Mike McCandless

http://blog.mikemccandless.com

On Mon, Apr 2, 2012 at 5:28 PM, Benson Margulies <bimargulies@gmail.com> wrote:
> We've observed something that, in some ways, is not surprising.
>
> If you take a set of documents that are close in 'score' to some query,
>
>  and shuffle them in different orders
>
>  and then see what results you get in what order from the reference query,
>
> the scores will vary according to the insertion order.
>
> I can't see any way to argue that it's wrong, but we find it
> inconvenient when we are testing something and we want to multithread
> the test to speed it up, thus making the insertion order
> nondeterministic.
>
> It occurred to me that perhaps you all have some similar concerns in
> testing lucene itself, and might have some advice about how to get
> around it, thus this email.
>
> We currently observe this with 2.9.1 and 3.5.0.
>
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