Class: Splashy::Buckets

Inherits:
Object
  • Object
show all
Defined in:
lib/splashy/buckets.rb

Instance Method Summary collapse

Constructor Details

#initialize(wanted_distribution, wanted_count = nil) ⇒ Buckets

wanted_distribution - A Hash of desired distributions:

{ :a => 0.2, :b => 0.5, :c => 0.3 }

wanted_count - (optional) Maximum total elements to be selected.

otherwise, the maximum size set is selected.



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# File 'lib/splashy/buckets.rb', line 7

def initialize( wanted_distribution, wanted_count=nil )
  unless wanted_distribution.values.inject(0){ |m,v| m + v } == 1.0
    raise ArgumentError.new( "Distribution must sum to 1.0" )
  end
  @wanted_distribution = wanted_distribution
  @wanted_count = wanted_count
  @buckets = Hash.new do |hash, name|
    hash[name] = Bucket.new( name )
  end
  @total_count = 0
end

Instance Method Details

#add(bucket_name, element) ⇒ Object

Public: Add a single element to a bucket.



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# File 'lib/splashy/buckets.rb', line 44

def add( bucket_name, element )
  @buckets[bucket_name] << element
  @total_count += 1
end

#fill(bucket_name = nil, &block) ⇒ Object

Public: Put elements into buckets.

bucket_name - If supplied, all yielded elements will be added to that

bucket.

&block - A block that returns (if ‘bucket_name` is not supplied)

an Array: [bucket_name, element]. If `bucket_name` is
supplied, only the element needs to be returned.

Examples

fill { return [bucket_name, element] }
fill( :bucket_name ) { return element }



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# File 'lib/splashy/buckets.rb', line 31

def fill( bucket_name = nil, &block )
  if bucket_name
    while element = yield( @total_count )
      self.add( bucket_name, element )
    end
  else
    while pair = yield( @total_count )
      self.add( *pair )
    end
  end
end

#satisfied? ⇒ Boolean

Returns true if the conditions are satisfied enough to select.

Returns:

  • (Boolean) 


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# File 'lib/splashy/buckets.rb', line 50

def satisfied?
  begin
    self.assert_satisfied!
    true
  rescue DistributionUnsatisfiedError => e
    false
  end
end

#select ⇒ Object

Public: Return a distribution of elements based on the desired distribution. If a satisfactory distribution is not possible, a DistributionUnsatisfiedError is raised.

Returns a Hash of elements based on the desired distribution, keyed by the bucket names.



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# File 'lib/splashy/buckets.rb', line 65

def select
  self.assert_satisfied!
  
  total_count = estimated_final_count
  
  selected = @wanted_distribution.keys.inject({}) do |memo, bucket_name|
    bucket = @buckets[bucket_name]
    count = total_count * @wanted_distribution[bucket_name]
    count = [1, count.round].max
    memo[bucket_name] = bucket.elements( count )
    memo
  end
  
  # Sometimes we need to fudge by a few to meet the `@wanted_count`
  selected = self.trim( selected ) if @wanted_count
  
  selected
end