Class: Hobix::Search::Simple::Vector

Inherits:
Object
  • Object
show all
Defined in:
lib/hobix/search/vector.rb

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize ⇒ Vector

Returns a new instance of Vector.



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# File 'lib/hobix/search/vector.rb', line 12

def initialize
    #    @bits = []
  @bits = 0
  @max_bit = -1
  @num_bits = 0
end

Instance Attribute Details

#at ⇒ Object

Returns the value of attribute at.



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# File 'lib/hobix/search/vector.rb', line 9

def at
  @at
end

#bits ⇒ Object (readonly)

Returns the value of attribute bits.



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# File 'lib/hobix/search/vector.rb', line 10

def bits
  @bits
end

#max_bit ⇒ Object (readonly)

Returns the value of attribute max_bit.



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# File 'lib/hobix/search/vector.rb', line 10

def max_bit
  @max_bit
end

#num_bits ⇒ Object (readonly)

Returns the value of attribute num_bits.



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# File 'lib/hobix/search/vector.rb', line 10

def num_bits
  @num_bits
end

Instance Method Details

#add_word_index(index) ⇒ Object 



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# File 'lib/hobix/search/vector.rb', line 19

def add_word_index(index)
  if @bits[index].zero?
    @bits += (1 << index)
    @num_bits += 1
    @max_bit = index if @max_bit < index
  end
end

#dot(vector) ⇒ Object 



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# File 'lib/hobix/search/vector.rb', line 27

def dot(vector)
  # We only need to calculate up to the end of the shortest vector
  limit = @max_bit
    # Commenting out the next line makes this vector the dominant
    # one when doing the comparison
  limit = vector.max_bit if limit > vector.max_bit
    
  # because both vectors have just ones or zeros in them,
  # we can pre-calculate the AnBn component
  # The vector's magnitude is Sqrt(num set bits)
  factor = Math.sqrt(1.0/@num_bits) * Math.sqrt(1.0/vector.num_bits)
    
  count = 0
  (limit+1).times {|i| count += 1 if @bits[i] ==1 && vector.bits[i] == 1}
    
  factor * count
end

#score_against(must_match, must_not_match, general) ⇒ Object

We’re a document’s vector, and we’re being matched against three other vectors:

  1. A list of must match words

  2. A list of must not match words

  3. A list of general words. The score we return is the number of these that we match



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# File 'lib/hobix/search/vector.rb', line 52

def score_against(must_match, must_not_match, general)
  # Eliminate if any _must_not_match_ words found
  unless must_not_match.num_bits.zero?
    return 0 unless (@bits & must_not_match.bits).zero?
  end
    
  # If the match was entirely negative, then we know we're passed at
  # this point
    
  if must_match.num_bits.zero? and general.num_bits.zero?
    return 1
  end
    
  count = 0
    
  # Eliminate unless all _must_match_ words found
    
  unless must_match.num_bits.zero?
    return 0 unless (@bits & must_match.bits) == must_match.bits
    count = 1
  end
    
  # finally score on the rest
  common = general.bits & @bits
  count += count_bits(common, @max_bit+1) unless common.zero?
  count
end