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Size: 1023 Bytes
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Contents
module Picky
module Generators
module Weights
# Uses a logarithmic weight.
# If for a key k we have x ids, the weight is:
# w(x): log(x)
# Special case: If x < 1, then we use 0.
#
class Logarithmic < Strategy
# Generates a partial index from the given inverted index.
#
def generate_from inverted
inverted.inject({}) do |hash, text_ids|
text, ids = *text_ids
weight = weight_for ids.size
hash[text] ||= weight.round(2) if weight
hash
end
end
# Sets the weight value.
#
# If the size is 0 or one, we would get -Infinity or 0.0.
# Thus we do not set a value if there is just one. The default, dynamically, is 0.
#
# BUT: We need the value, even if 0. To designate that there is a weight!
#
def weight_for amount
return 0 if amount < 1
Math.log amount
end
end
end
end
end
Version data entries
5 entries across 5 versions & 1 rubygems