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From "Charlie Zhao (JIRA)" <>
Subject [jira] Commented: (LUCENE-965) Implement a state-of-the-art retrieval function in Lucene
Date Thu, 26 Jul 2007 17:10:05 GMT


Charlie Zhao commented on LUCENE-965:

Hello Hui:

Thank you for contributing your axiomatic retrieval function to Lucene. Can not wait for the
test drive.

Would you please report your settings for your experiment on

´╗┐Collection     Function                 MAP     P5     P10     P20     P100     NumRR
ROBUST04    Lucene Default     0.048     0.12 0.09     0.08     0.05     21

Since there are disparities comparing with mine.

num_q     249
num_ret     239436
num_rel     17412
num_rel_ret     9780
map     0.2076
gm_ap     0.1049
R-prec     0.2551
bpref     0.2189
recip_rank     0.5684
ircl_prn.0.00     0.6288
ircl_prn.0.10     0.4459
ircl_prn.0.20     0.3562
ircl_prn.0.30     0.2864
ircl_prn.0.40     0.2289
ircl_prn.0.50     0.1925
ircl_prn.0.60     0.145
ircl_prn.0.70     0.1062
ircl_prn.0.80     0.0702
ircl_prn.0.90     0.0461
ircl_prn.1.00     0.0261
P5     0.3944
P10     0.3598
P15     0.3307
P20     0.307
P30     0.2657
P100     0.1618
P200     0.1117
P500     0.0635
P1000     0.0393

Before we go further, let us make sure we are in the same page.

Here is my setting:

    Data: TREC Disk 4 & 5; 528,155 documents; 1,904 MB of text.

    Query Number: TREC Query Number 301-700

    Query Field: <title> only

    IR Engine: Lucene 2.0 (need double check, but close:)

    Note: default Lucene similarity function, using title words only.

If we are in the same page, then 0.048 MAP score is terribly low for 301-700, whereas 0.2076
in mine.

Still your axiomatic retrieval function outperformed the default in many other aspects. So
if you would like to check your experimental setting, and if my result is more closer to the
real default, then we might discover a further improvement with the axiomatic retrieval function.
That is my hope. 

Charlie Zhao

> Implement a state-of-the-art retrieval function in Lucene
> ---------------------------------------------------------
>                 Key: LUCENE-965
>                 URL:
>             Project: Lucene - Java
>          Issue Type: Improvement
>          Components: Search
>    Affects Versions: 2.2
>            Reporter: Hui Fang
>         Attachments: axiomaticFunction.patch
> We implemented the axiomatic retrieval function, which is a state-of-the-art retrieval
function, to 
> replace the default similarity function in Lucene. We compared the performance of these
two functions and reported the results at

> The report shows that the performance of the axiomatic retrieval function is much better
than the default function. The axiomatic retrieval function is able to find more relevant
documents and users can see more relevant documents in the top-ranked documents. Incorporating
such a state-of-the-art retrieval function could improve the search performance of all the
applications which were built upon Lucene. 
> Most changes related to the implementation are made in AXSimilarity, TermScorer and
 However, many test cases are hand coded to test whether the implementation of the default
function is correct. Thus, I also made the modification to many test files to make the new
retrieval function pass those cases. In fact, we found that some old test cases are not reasonable.
For example, in the testQueries02 of, 
> the query is "+w3 xx", and we have two documents "w1 xx w2 yy w3" and "w1 w3 xx w2 yy
> The second document should be more relevant than the first one, because it has more 
> occurrences of the query term "w3". But the original test case would require us to rank

> the first document higher than the second one, which is not reasonable. 

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