Hi, Floats require 32 bits but norms are encoded on a single byte. So there is a precision loss when encoding float values into a single byte. In your example, 0.75 and 0.89 are sufficiently close to each other so that they are encoded to the same byte.
On Wed, Mar 4, 2015 at 4:48 AM, wangdong <hrdxwa...@gmail.com> wrote: > I read the article about the scoring section in lucene as follows: > > Encoding and decoding of the resulted float norm in a single byte are done > by the static methods of the class Similarity:encodeNorm() > <http://lucene.apache.org/core/3_6_1/api/core/org/apache/lucene/search/Similarity.html#encodeNorm%28float%29>anddecodeNorm() > <http://lucene.apache.org/core/3_6_1/api/core/org/apache/lucene/search/Similarity.html#decodeNorm%28byte%29>. > Due to loss of precision, it is not guaranteed that decode(encode(x)) = x, > e.g. decode(encode(0.89)) = 0.75. At scoring (search) time, this norm is > brought into the score of document as*norm(t, d)*, as shown by the formula > inSimilarity > <http://lucene.apache.org/core/3_6_1/api/core/org/apache/lucene/search/Similarity.html>. > > I can not understand the formula decode(encode(0.89)) = 0.75 > how can i get the 0.75 from the left. > > Is anyone can help me ? > thanks ahead! > > andrew -- Adrien --------------------------------------------------------------------- To unsubscribe, e-mail: java-user-unsubscr...@lucene.apache.org For additional commands, e-mail: java-user-h...@lucene.apache.org
