Fibonacci Comparison

fibonacci.rb

# Naive slow implementation
def simple_fib(n)
    return n if (0..1).include?(n)
    simple_fib(n - 1) + simple_fib(n - 2)
end

# Recursive fast implementation
def rec_fib(n)
    rec = -> (a, b, n) { n == 0 ? a : rec.call(b, a + b, n - 1) }
    rec.call(0, 1, n)
end

# Benchmark
require 'benchmark'

n = 30
Benchmark.bm(11) do |x|
  x.report("simple_fib:") { (0..n).map { |i| simple_fib(i) } }
  x.report("rec_fib:")    { (0..n).map { |i| rec_fib(i) } }
end

#                   user     system      total        real
# simple_fib:   1.360000   0.000000   1.360000 (  1.364467)
# rec_fib:      0.000000   0.000000   0.000000 (  0.000156)