|
||||||||||
PREV CLASS NEXT CLASS | FRAMES NO FRAMES | |||||||||
SUMMARY: NESTED | FIELD | CONSTR | METHOD | DETAIL: FIELD | CONSTR | METHOD |
java.lang.Objectit.unimi.dsi.mg4j.search.score.AbstractScorer
it.unimi.dsi.mg4j.search.score.ClarkeCormackScorer
Computes the Clarke-Cormack score of all interval iterators of a document.
This score function is defined in Shortest-Substring
Retrieval and Ranking (ACM Transactions on Information Systems, vol. 18, no. 1, Jan 2000,
pages 44-78), at page 65; the weight assigned to different indices is the same for all indices
(but it may be rewritten by subclasses, rewriting the AbstractScorer.weight(Index)
method).
The score depends on two parameters: an integer h
and a double alpha
.
The score is obtained summing up a certain score assigned to all intervals in the interval iterator
produced on that document for the given query. The score assigned to an interval is 1 if the interval
has length smaller than h
; otherwise, it is obtained by dividing h
by
the interval length, and raising the result to the power of alpha
.
Note that the score assigned to each interval is between 0 and 1 (highest scores corresponding to best intervals). The score assigned to an interval iterator is thus bounded from above by the number of intervals.
Typically, one sets h
=16 (or a bit larger) and alpha
=1 (or a bit smaller),
but the authors say that the method is rather stable w.r.t. changes in the values of parameters.
Constructor Summary | |
ClarkeCormackScorer()
Default constructor, assigning the default values ( h =16, alpha =1) to the
parameter. |
|
ClarkeCormackScorer(int h,
double alpha)
Creates a scorer with given parameter. |
Method Summary | |
protected double |
score(IntervalIterator it)
Computes the Clarke-Cormack score of an interval iterator. |
Methods inherited from class it.unimi.dsi.mg4j.search.score.AbstractScorer |
score, scoredDocumentIterator, weight |
Methods inherited from class java.lang.Object |
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
Constructor Detail |
public ClarkeCormackScorer(int h, double alpha)
h
- the parameter h.alpha
- the parameter alpha.public ClarkeCormackScorer()
h
=16, alpha
=1) to the
parameter.
Method Detail |
protected double score(IntervalIterator it)
score
in class AbstractScorer
it
- the iterator.
|
||||||||||
PREV CLASS NEXT CLASS | FRAMES NO FRAMES | |||||||||
SUMMARY: NESTED | FIELD | CONSTR | METHOD | DETAIL: FIELD | CONSTR | METHOD |