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https://issues.apache.org/jira/browse/SOLR-2754?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13106924#comment-13106924
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Robert Muir commented on SOLR-2754:
-----------------------------------
{quote}
I can understand the reasoning behind this idea. On the other hand, for some
models, the parameter has a value that's optimal in a wide range of cases. In
such cases, I think it we could make the life of the user easier by falling
back to this value. (Actually, that's why LMJelinekMercerSimilarity does not
have a default constructor; there is no single parameter value that is
kind-of-optimal in all cases).
{quote}
Well, we can do both: we can provide these basic parameters as default values
to be friendly, but at the same time in the test or example xml configurations
that use these, our examples can have the parameters set. Even in the
JelinekMercer case, our example can also be set to 0.7, because thats the
default for long queries and you typically don't use this smoothing for short
queries (you would usually use Dirichlet instead), at least that was my
reasoning with the default.
{quote}
Yes, I know, it'd be a bit difficult to support that... maybe if all
Similarities and models had a constructor with a map as a parameter? I'm not
sure we want that, though.
{quote}
Yeah, I think we want to have hard type-safe apis for the sims themselves, and
part of my line of thinking is the case of "I'm going to plug in a custom
normalization into DFR" is a pretty expert case for a Solr user at this moment,
if you are that expert you could also write a 3 LOC sim factory that sets up
your sim with your custom normalization method.
> create Solr similarity factories for new ranking algorithms
> -----------------------------------------------------------
>
> Key: SOLR-2754
> URL: https://issues.apache.org/jira/browse/SOLR-2754
> Project: Solr
> Issue Type: New Feature
> Affects Versions: 4.0
> Reporter: Robert Muir
> Assignee: Robert Muir
> Attachments: SOLR-2754.patch
>
>
> To make it easy to use some of the new ranking algorithms, we should add
> factories to solr:
> * for parametric models like LM and BM25 so that parameters can be set from
> schema.xml
> * for framework models like DFR and IB, so that different basic
> models/normalizations/lambdas can be chosen
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