Fibonacci algorithm

gistfile1.txt

def self.fib(quantity)
  start  = [0,1]
  quantity.times do
    two_numbers = start.last(2)
    start <<  two_numbers.inject{|sum, n| sum +n}
  end
  start
end

def self.fibonacci(quantity)
  serie  = [0,1]
  quantity.times do
    serie <<  serie.last(2).inject(:+)
  end
  serie
end

def self.fibonacci_express(quantity)
  serie  = [0,1]
  for i in 1..quantity do
    serie <<  serie.last(2).inject(:+)
  end
  serie
end

def self.fibonacci_uber(quantity)
  serie = [0,1]
  quantity.times do
    serie << serie.last(2).inject(:+)
  end
  serie
end

Benchmark.bm do |x|
  x.report("fib: ") { fib(50) }
  x.report("fibonacci: ") { fibonacci(50) }
end
            user       system      total        real
fib:        0.000000   0.000000   0.000000 (  0.000228)
fibonacci:  0.000000   0.000000   0.000000 (  0.000240)

Benchmark.bm do |x|
 x.report("fib: ") { 100.times{fib(50)} }
 x.report("fibonacci: ") { 100.times{fibonacci(50)} }
end
             user       system      total        real
fib:         0.000000   0.000000   0.000000 (  0.007202)
fibonacci:   0.010000   0.000000   0.010000 (  0.004343)


Benchmark.bm do |x|
 x.report("fibonacci: "){ fibonacci(50) }
 x.report("fibonacci_express: "){ fibonacci_express(50)}
end
                      user      system      total        real
fibonacci:           0.000000   0.000000   0.000000 (  0.000215)
fibonacci_express:   0.000000   0.000000   0.000000 (  0.000144)



Benchmark.bm do |x|
 x.report("fibonacci: "){ fibonacci(50000) }
 x.report("fibonacci_express: "){ fibonacci_express(50000) }
end
                      user     system      total        real
fibonacci:           0.130000   0.040000   0.170000 (  0.186078)
fibonacci_express:   0.110000   0.020000   0.130000 (  0.145938)


Benchmark.bm do |x|
 x.report("fibonacci: "){ fibonacci(500000) }
 x.report("fibonacci_express: ") {fibonacci_express(500000)}
end
                    user     system      total        real
fibonacci:         7.600000  12.740000  20.340000 (967.804414)
fibonacci_express: 14.170000  84.060000  98.230000 (4783.423653)

Benchmark.bm do |x|
  x.report{ fibonacci_uber(50) }
end
                  user       system      total        real
fibonacci_uber:   0.000000   0.000000   0.000000 (  0.000110)


Benchmark.bm do |x|
 x.report("fibonacci_uber: "){ fibonacci_uber(50000) }
end
                   user     system      total        real
fibonacci_uber:   0.240000   2.540000   2.780000 (171.997193)