Thanks Tom! I think I've seen a good explanation of tie from Hoss once.... something that described the background for tie beyond "it's good for breaking score ties between two documents". For example, what are the scenarios where one can expect or fear scoring ties between multiple documents whose scores come from a single field? When multiple documents have very similar or identical values of certain fields that are used in search and that tend to provide high scores and/or have high boosts?
Consider the situation where you are indexing documents that have 2 fields, author and body, there are very few distinct authors, and the author field has high boost (plus it's short) and your query is the name of the author. Is this the situation where the author field is likely to end up being the field with max score and multiple documents (with the same author) are likely to have the same score if you take that max score on the author field as the final score for the document? Is that the scenario where tie is very important? Are there other scenarios that are different enough from the above worth describing on the Wiki? Thanks, Otis ---- Sematext :: http://sematext.com/ :: Solr - Lucene - Nutch Lucene ecosystem search :: http://search-lucene.com/ ----- Original Message ---- > From: "Burton-West, Tom" <tburt...@umich.edu> > To: Chris Hostetter <hossman_luc...@fucit.org>; "solr-user@lucene.apache.org" ><solr-user@lucene.apache.org>; "yo...@lucidimagination.com" ><yo...@lucidimagination.com> > Sent: Fri, April 15, 2011 11:55:03 AM > Subject: RE: Understanding the DisMax tie parameter > > Thanks everyone. > > I updated the wiki. If you have a chance please take a look and check to > make >sure I got it right on the wiki. > > http://wiki.apache.org/solr/DisMaxQParserPlugin#tie_.28Tie_breaker.29 > > Tom > > > > -----Original Message----- > From: Chris Hostetter [mailto:hossman_luc...@fucit.org] > Sent: Thursday, April 14, 2011 5:41 PM > To: solr-user@lucene.apache.org; yo...@lucidimagination.com > Cc: Burton-West, Tom > Subject: Re: Understanding the DisMax tie parameter > > > : Perhaps the parameter could have had a better name. It's essentially > : max(score of matching clauses) + tie * (score of matching clauses that > : are not the max) > : > : So it can be used and thought of as a tiebreak only in the sense that > : if two docs match a clause (with essentially the same score), then a > : small tie value will act as a tiebreaker *if* one of those docs also > : matches some other fields. > > correct. w/o a tiebreaker value, a dismax query will only look at the > maximum scoring clause for each doc -- the "tie" param is named for it's > ability to help break ties when multiple documents have the same score > from the max scoring clause -- by adding in a small portion of the scores > (based on the 0->1 ratio of the "tie" param) from the other clauses. > > > -Hoss >
