Class BM25Similarity

BM25 with these default values:

• k1 = 1.2,
• b = 0.75.

BM25 with the supplied parameter values.

Returns the b parameter

Gets or Sets whether overlap tokens (Tokens with 0 position increment) are ignored when computing norm. By default this is true, meaning overlap tokens do not count when computing norms.

Returns the k1 parameter

The default implementation computes the average as sumTotalTermFreq / maxDoc, or returns 1 if the index does not store sumTotalTermFreq (Lucene 3.x indexes or any field that omits frequency information).

The default implementation returns 1 / f2 where f is Byte315ToSingle(Byte).

The default implementation encodes boost / sqrt(length) with SingleToByte315(Single). This is compatible with Lucene's default implementation. If you change this, then you should change DecodeNormValue(Byte) to match.

Implemented as log(1 + (numDocs - docFreq + 0.5)/(docFreq + 0.5)).

Computes a score factor for a simple term and returns an explanation for that score factor.

The default implementation uses:

    Idf(docFreq, searcher.MaxDoc);

Note that MaxDoc is used instead of Lucene.Net.Index.IndexReader.IntNumDocs because also DocFreq is used, and when the latter is inaccurate, so is MaxDoc, and in the same direction. In addition, MaxDoc is more efficient to compute

Computes a score factor for a phrase.

The default implementation sums the idf factor for each term in the phrase.

The default implementation returns 1

Implemented as 1 / (distance + 1).