fib.rb

require 'benchmark'
@cache = Hash.new

def fibonacci_cache(n)
  if t = @cache[n]
    return t
  end
  if n <= 1
    return 1
  else
    result = fibonacci_cache(n-1) + fibonacci_cache(n-2)
  end
  @cache[n] = result
end

def fibonacci(n)
  if n <= 1
    return 1
  else
    fibonacci(n-1) + fibonacci(n-2)
  end
end

puts Benchmark.measure{fibonacci(40)}
puts Benchmark.measure{fibonacci_cache(40)}