pi / malloc / ubuntu

pi.rb

#
# ruby pi - how to calculate pi with ruby.
# proving that pi is the limit of this series:
# 4/1 - 4/3 + 4/5 - 4/7 + 4/9 ...
#
num = 4.0
pi = 0
plus = true

den = 1
while den < 100000000
  if plus
    pi = pi + num/den
    plus = false
  else
    pi = pi - num/den
    plus = true
  end
  den = den + 2
end

puts "PI = #{pi}"              # calculated value of pi
puts "Math::PI = #{Math::PI}"  # pi from the math class

rvm ruby2.1.rb

vagrant@precise64:~$ time ruby pi.rb
PI = 3.1415926335902506
Math::PI = 3.141592653589793

real	0m3.368s
user	0m3.352s
sys	0m0.016s

source ruby2.1-jmalloc.rb

vagrant@precise64:~/ruby-2.1.0$ ./configure LIBS=-ljemalloc
https://www.ruby-forum.com/topic/4418556
http://leonard.io/blog/2012/05/installing-ruby-1-9-3-on-ubuntu-12-04-precise-pengolin/


vagrant@precise64:~$ time ruby pi.rb
PI = 3.1415926335902506
Math::PI = 3.141592653589793

real	0m3.231s
user	0m3.220s
sys	0m0.008s

system ruby187.rb

vagrant@precise64:~$ time ruby pi.rb
PI = 3.14159263359025
Math::PI = 3.14159265358979

real	0m21.406s
user	0m21.397s
sys	0m0.000s
vagrant@precise64:~$ ruby -v
ruby 1.8.7 (2012-02-08 patchlevel 358) [x86_64-linux]