Is there a performance gain in using single quotes vs double quotes in ruby?

dimus_23080 0
Viewed 25870

Do you know if using double quotes instead of single quotes in ruby decreases performance in any meaningful way in ruby 1.8 and 1.9.

so if I type 

question = 'my question'

is it faster than 

question = "my question"

I imagine that ruby tries to figure out if something needs to be evaluated when it encounters double quotes and probably spends some cycles doing just that.

syntax ruby performance
14 Answers

No one happened to measure concatenation vs interpolation though:

$ ruby -v
ruby 1.8.7 (2008-08-11 patchlevel 72) [i686-darwin9.6.2]
$ cat benchmark_quotes.rb
require 'benchmark'
n = 1000000
Benchmark.bm do |x|
  x.report("assign single") { n.times do; c = 'a string'; end}
  x.report("assign double") { n.times do; c = "a string"; end}
  x.report("assign interp") { n.times do; c = "a string #{'b string'}"; end}
  x.report("concat single") { n.times do; 'a string ' + 'b string'; end}
  x.report("concat double") { n.times do; "a string " + "b string"; end}
end

$ ruby -w benchmark_quotes.rb 
      user     system      total        real
assign single  2.600000   1.060000   3.660000 (  3.720909)
assign double  2.590000   1.050000   3.640000 (  3.675082)
assign interp  2.620000   1.050000   3.670000 (  3.704218)
concat single  3.760000   1.080000   4.840000 (  4.888394)
concat double  3.700000   1.070000   4.770000 (  4.818794)

Specifically, note assign interp = 2.62 vs concat single = 3.76. As icing on the cake, I also find interpolation to be more readable than 'a' + var + 'b' especially with regard to spaces.

user_2535230

I too thought that single quoted strings might be quicker to parse for Ruby. It doesn't seem to be the case.

Anyway, I think the above benchmark are measuring the wrong thing, though. It stands to reason that either versions will be parsed into the same internal string representations so to get the answer as to which is quicker to parse, we shouldn't be measuring performance with string variables, but rather Ruby's speed of parsing strings.

generate.rb: 
10000.times do
  ('a'..'z').to_a.each {|v| print "#{v}='This is a test string.'\n" }
end

#Generate sample ruby code with lots of strings to parse
$ ruby generate.rb > single_q.rb
#Get the double quote version
$ tr \' \" < single_q.rb > double_q.rb

#Compare execution times
$ time ruby single_q.rb 

real    0m0.978s
user    0m0.920s
sys     0m0.048s
$ time ruby double_q.rb 

real    0m0.994s
user    0m0.940s
sys     0m0.044s

Repeated runs don't seem to make much difference. It still takes pretty much the same time to parse either version of the string.

user_10847740
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