Examples of org.apache.lucene.search.Similarity.lengthNorm()

Class org.apache.lucene.search.Similarity

Examples of org.apache.lucene.search.Similarity.lengthNorm()

org.apache.lucene.search.Similarity.lengthNorm()
Computes the normalization value for a field given the total number of terms contained in a field. These values, together with field boosts, are stored in an index and multipled into scores for hits on each field by the search code.
Matches in longer fields are less precise, so implementations of this method usually return smaller values when numTokens is large, and larger values when numTokens is small.
Note that the return values are computed under {@link org.apache.lucene.index.IndexWriter#addDocument(org.apache.lucene.document.Document)} and then stored using {@link #encodeNorm(float)}. Thus they have limited precision, and documents must be re-indexed if this method is altered. @param fieldName the name of the field @param numTokens the total number of tokens contained in fields namedfieldName of doc. @return a normalization factor for hits on this field of this document @see org.apache.lucene.document.Field#setBoost(float)


    // base case, should degrade
  
    for (int i = 1; i < 1000; i++) {
      assertEquals("base case: i="+i,
                   d.lengthNorm("foo",i), s.lengthNorm("foo",i),
                   0.0f);
    }


    // make a sweet spot

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    ss.setLengthNormFactors(3,10,0.5f);
  
    for (int i = 3; i <=10; i++) {
      assertEquals("3,10: spot i="+i,
                   1.0f, s.lengthNorm("foo",i),
                   0.0f);
    }
  
    for (int i = 10; i < 1000; i++) {
      assertEquals("3,10: 10<x : i="+i,

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                   0.0f);
    }
  
    for (int i = 10; i < 1000; i++) {
      assertEquals("3,10: 10<x : i="+i,
                   d.lengthNorm("foo",i-9), s.lengthNorm("foo",i),
                   0.0f);
    }




    // seperate sweet spot for certain fields

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    ss.setLengthNormFactors("yak",6,9, 0.5f, false);


  
    for (int i = 3; i <=10; i++) {
      assertEquals("f: 3,10: spot i="+i,
                   1.0f, s.lengthNorm("foo",i),
                   0.0f);
    }
    for (int i = 10; i < 1000; i++) {
      assertEquals("f: 3,10: 10<x : i="+i,
                   d.lengthNorm("foo",i-9), s.lengthNorm("foo",i),

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                   1.0f, s.lengthNorm("foo",i),
                   0.0f);
    }
    for (int i = 10; i < 1000; i++) {
      assertEquals("f: 3,10: 10<x : i="+i,
                   d.lengthNorm("foo",i-9), s.lengthNorm("foo",i),
                   0.0f);
    }
    for (int i = 8; i <=13; i++) {
      assertEquals("f: 8,13: spot i="+i,
                   1.0f, s.lengthNorm("bar",i),

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                   d.lengthNorm("foo",i-9), s.lengthNorm("foo",i),
                   0.0f);
    }
    for (int i = 8; i <=13; i++) {
      assertEquals("f: 8,13: spot i="+i,
                   1.0f, s.lengthNorm("bar",i),
                   0.0f);
    }
    for (int i = 6; i <=9; i++) {
      assertEquals("f: 6,9: spot i="+i,
                   1.0f, s.lengthNorm("yak",i),

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                   1.0f, s.lengthNorm("bar",i),
                   0.0f);
    }
    for (int i = 6; i <=9; i++) {
      assertEquals("f: 6,9: spot i="+i,
                   1.0f, s.lengthNorm("yak",i),
                   0.0f);
    }
    for (int i = 13; i < 1000; i++) {
      assertEquals("f: 8,13: 13<x : i="+i,
                   d.lengthNorm("foo",i-12), s.lengthNorm("bar",i),

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                   1.0f, s.lengthNorm("yak",i),
                   0.0f);
    }
    for (int i = 13; i < 1000; i++) {
      assertEquals("f: 8,13: 13<x : i="+i,
                   d.lengthNorm("foo",i-12), s.lengthNorm("bar",i),
                   0.0f);
    }
    for (int i = 9; i < 1000; i++) {
      assertEquals("f: 6,9: 9<x : i="+i,
                   d.lengthNorm("foo",i-8), s.lengthNorm("yak",i),

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                   d.lengthNorm("foo",i-12), s.lengthNorm("bar",i),
                   0.0f);
    }
    for (int i = 9; i < 1000; i++) {
      assertEquals("f: 6,9: 9<x : i="+i,
                   d.lengthNorm("foo",i-8), s.lengthNorm("yak",i),
                   0.0f);
    }




    // steepness

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    ss.setLengthNormFactors("b",5,8,0.1f, false);


    for (int i = 9; i < 1000; i++) {
      assertTrue("s: i="+i+" : a="+ss.lengthNorm("a",i)+
                 " < b="+ss.lengthNorm("b",i),
                 ss.lengthNorm("a",i) < s.lengthNorm("b",i));
    }


  }


  public void testSweetSpotTf() {

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