Fibonacci sequences in an iterative and recursive manner in Ruby

fib.rb

class Fib
  
  @tracking = [0,1]
  
  def self.iter_compute(index)
    tracking = [0,1]   
    index.times do |i|
      tracking << tracking[-2] + tracking[-1]
      tracking.shift if tracking.size > 2
    end
    return tracking[-2]
  end
  
  def self.compute(index)
    if @tracking[index].nil?
      @tracking[index] = compute(index - 1) + compute(index - 2)
    else
      @tracking[index]
    end
  end
end

p Fib.iter_compute(7500)
#p Fib.compute(7500)

p [Fib.compute(0), Fib.compute(0) == 0]
p [Fib.compute(1), Fib.compute(1) == 1]

p [Fib.compute(5), Fib.compute(5) == 5]
p [Fib.compute(6), Fib.compute(6) == 8]
p [Fib.compute(10), Fib.compute(10) == 55]