From: Colin Bartlett <colinb2r@...>
Date: 2011-03-23T00:31:42+09:00
Subject: Re: summing values in a hash?

On Tue, Mar 22, 2011 at 12:57 PM, Jen <jen.bottom@gmail.com> wrote:
> Is there an inbuilt method to sum all values in a hash and return the
> result?
> I.E something like puts hash[values].sum
> If so could someone please point me at the correct section of the ruby docs?

Maybe write your own method because:
1. it may be quicker than searching for an "inbuilt" method;
2. it may run faster than using inject.

require "benchmark"
kt = 100_000
nn = 20

hash = Hash.new
(1 .. nn).each { |nv| hash[ nv.to_s ] = nv }
s1 = s2 = s3 = s4 = nil

class Hash
  def mysum()
    s = 0
    each_value { |v| s += v }
    s
  end
end

sv = (nn * (nn + 1)) / 2
puts; puts "summing 1..#{nn} #=> #{sv};  kt=#{kt};"

Benchmark.bmbm do |bm|
  bm.report("1"){kt.times{s1=hash.values.inject{ |a, b| a + b } }}
  bm.report("2"){kt.times{s2=hash.inject(0){ |sum, tuple| sum += tuple[1] } }}
  bm.report("3"){kt.times{s3=hash.inject(0){|a,(_,b)|a+b} }}
  bm.report("4"){kt.times{s4=hash.mysum }}
end
puts "#{s1.inspect}  #{s2.inspect}  #{s3.inspect}  #{s4.inspect}"


ruby 1.9.1p430 (2010-08-16 revision 28998) [i386-mingw32]

summing 1..20 #=> 210;  kt=100000;
        user     system      total        real
1   3.057000   0.000000   3.057000 (  3.057547)
2   4.587000   0.000000   4.587000 (  4.630071)
3   4.524000   0.000000   4.524000 (  4.525069)
4   1.653000   0.000000   1.653000 (  1.650026)
210  210  210  210

summing 1..2000 #=> 2001000;  kt=1000;
        user     system      total        real
1   2.340000   0.000000   2.340000 (  2.335036)
2   4.711000   0.000000   4.711000 (  4.705072)
3   4.617000   0.000000   4.617000 (  4.635071)
4   1.529000   0.000000   1.529000 (  1.530024)
2001000  2001000  2001000  2001000