Class: TextAlignment::AnchorFinder

Inherits:
Object
  • Object
show all
Defined in:
lib/text_alignment/anchor_finder.rb

Instance Method Summary collapse

Constructor Details

#initialize(source_str, target_str, cultivation_map, to_ignore_whitespaces = false, to_ignore_text_order = false) ⇒ AnchorFinder

Returns a new instance of AnchorFinder.



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# File 'lib/text_alignment/anchor_finder.rb', line 9

def initialize(source_str, target_str, cultivation_map, to_ignore_whitespaces = false, to_ignore_text_order = false)
  @method_get_left_windows, @method_get_right_windows = if to_ignore_whitespaces
    [method(:get_left_windows_no_squeeze_ws), method(:get_right_windows_no_squeeze_ws)]
  else
    [method(:get_left_windows), method(:get_right_windows)]
  end

  @s1 = source_str.downcase
  @s2 = target_str.downcase

  @cultivation_map = cultivation_map
  @to_ignore_text_order = to_ignore_text_order

  @size_ngram  = TextAlignment::SIZE_NGRAM
  @size_window = TextAlignment::SIZE_WINDOW
  @sim_threshold = TextAlignment::TEXT_SIMILARITY_THRESHOLD
  @pos_s1_final_possible_begin = @s1.length - @size_ngram - 1
  @pos_s2_final_possible_end = @s2.length

  # positions of last match
  @pos_s1_last_match = 0
  @pos_s2_last_match = 0

  # Performance: cache for character classification
  @half_ngram = @size_ngram / 2
end

Instance Method Details

#get_next_anchor ⇒ Object 



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# File 'lib/text_alignment/anchor_finder.rb', line 36

def get_next_anchor
  # To find the beginning positions of an anchor ngram in s1 and s2, beginning from the last positions matched
  iterations = 0
  beg_s2 = for beg_s1 in @pos_s1_last_match .. @pos_s1_final_possible_begin
    iterations += 1

    char = @s1[beg_s1]

    # To skip whitespace letters
    next if char == ' ' || char == "\n" || char == "\t"

    # Skip positions that start with punctuation or numbers (likely poor anchors)
    next if char < 'A' || (char > 'Z' && char < 'a') || char > 'z'

    # Performance optimization: skip if we've had too many failed attempts recently
    if iterations > 50 && @recent_failures && @recent_failures > 10
      step_size = [@recent_failures / 5, 3].min
      beg_s1 += step_size
      next if beg_s1 > @pos_s1_final_possible_begin
    end

    _beg_s2 = get_beg_s2(beg_s1)

    if _beg_s2.nil?
      @recent_failures = (@recent_failures || 0) + 1
    else
      @recent_failures = 0  # Reset on success
    end

    break _beg_s2 unless _beg_s2.nil?
  end

  # To return nil when it fails to find an anchor
  return nil if beg_s2.class == Range

  # To extend the block to the left
  b1 = beg_s1
  b2 = beg_s2
  left_boundary_b2 = [@pos_s2_last_match, (@cultivation_map.last_cultivated_position(b2) || 0)].max
  while b1 > @pos_s1_last_match && b2 > left_boundary_b2 && @s1[b1 - 1] == @s2[b2 - 1]
    b1 -= 1; b2 -= 1
  end

  # To extend the block to the right
  e1 = beg_s1 + @size_ngram
  e2 = beg_s2 + @size_ngram
  right_boundary_b2 = @cultivation_map.next_cultivated_position(e2) || @pos_s2_final_possible_end
  while @s1[e1] && e2 < right_boundary_b2 && @s1[e1] == @s2[e2]
    e1 += 1; e2 += 1
  end

  @pos_s1_last_match = e1
  @pos_s2_last_match = e2

  {source:{begin:b1 , end:e1}, target:{begin:b2, end:e2}}
end