# String performance

**URL:** <https://www.ruby-forum.com/t/string-performance/81552>\
**Category:** Ruby\
**Created:** [January 9, 2007, 9:47pm UTC](https://www.ruby-forum.com/t/string-performance/81552 "2007-01-09T21:47:06Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![simplydope](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/d26b3c/32.png) [@simplydope](https://www.ruby-forum.com/u/simplydope)\
**Post date:** [January 9, 2007, 9:47pm UTC](https://www.ruby-forum.com/t/string-performance/81552/1 "2007-01-09T21:47:06Z")

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Guys a quick performance question - Is either one of the following more  
efficient than the other? I’m guessing they’re in this order:

‘a’ + x + ‘b’  
“a” + x + “b”  
“a#{x}b”

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**Author:** ![simplydope](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/d26b3c/32.png) [@simplydope](https://www.ruby-forum.com/u/simplydope)\
**Post date:** [January 9, 2007, 9:54pm UTC](https://www.ruby-forum.com/t/string-performance/81552/2 "2007-01-09T21:54:47Z")

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George P. wrote:

> Guys a quick performance question - Is either one of the following more  
> efficient than the other? I’m guessing they’re in this order:
> 
> ‘a’ + x + ‘b’  
> “a” + x + “b”  
> “a#{x}b”

Exactly the opposite:

21:52 vincent@tanyaivinco ~/Prog/Ruby ruby rt\_7.rb  
user system total real  
0.010000 0.000000 0.010000 ( 0.009087)  
0.010000 0.000000 0.010000 ( 0.008774)  
0.000000 0.000000 0.000000 ( 0.004621)

rt\_7.rb is

require ‘benchmark’

n = 5000  
c = “stuff”  
Benchmark.bm do |x|  
x.report { n.times {‘a’ + c + ‘b’}}  
x.report { n.times {“a” + c + “b”}}  
x.report { n.times {“a#{c}b”}}  
end

If you’re looking for a performance question, Benchmark is nearly  
always your answer.

Vince

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<div class="post-metadata">

**Author:** ![simplydope](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/d26b3c/32.png) [@simplydope](https://www.ruby-forum.com/u/simplydope)\
**Post date:** [January 9, 2007, 9:58pm UTC](https://www.ruby-forum.com/t/string-performance/81552/3 "2007-01-09T21:58:15Z")

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Wow thanks Vince I knew you could benchmark somehow but I wasn’t sure  
how. I’m now off to make a few code changes…

Vincent F. wrote:

> Exactly the opposite:
> 
> 21:52 vincent@tanyaivinco ~/Prog/Ruby ruby rt\_7.rb  
> user system total real  
> 0.010000 0.000000 0.010000 ( 0.009087)  
> 0.010000 0.000000 0.010000 ( 0.008774)  
> 0.000000 0.000000 0.000000 ( 0.004621)  
> …

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<div class="post-metadata">

**Author:** ![simplydope](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/d26b3c/32.png) [@simplydope](https://www.ruby-forum.com/u/simplydope)\
**Post date:** [January 9, 2007, 10:16pm UTC](https://www.ruby-forum.com/t/string-performance/81552/4 "2007-01-09T22:16:50Z")

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On Jan 9, 2007, at 12:53, Vincent F. wrote:

> 21:52 vincent@tanyaivinco ~/Prog/Ruby ruby rt\_7.rb  
> user system total real  
> 0.010000 0.000000 0.010000 ( 0.009087)  
> 0.010000 0.000000 0.010000 ( 0.008774)  
> 0.000000 0.000000 0.000000 ( 0.004621)
> 
> rt\_7.rb is

Could be improved:

$ cat rt\_7.rb  
require ‘benchmark’

n = 5\_000\_000  
c = “stuff”  
Benchmark.bmbm do |x|  
x.report(‘'a' +’) { n.times {‘a’ + c + ‘b’}}  
x.report(‘“a” +’) { n.times {“a” + c + “b”}}  
x.report(‘a#{’) { n.times {“a#{c}b”}}  
end

$ ruby rt\_7.rb  
Rehearsal -----------------------------------------  
‘a’ + 6.090000 0.010000 6.100000 ( 6.183097)  
“a” + 6.110000 0.010000 6.120000 ( 6.114159)  
a#{ 3.280000 0.000000 3.280000 ( 3.298253)  
------------------------------- total: 15.500000sec

```
         user system total real

```

‘a’ + 6.130000 0.010000 6.140000 ( 6.155325)  
“a” + 6.140000 0.000000 6.140000 ( 6.155082)  
a#{ 3.300000 0.010000 3.310000 ( 3.312989)

Further increases in n will show ’ strings and " strings completely  
converging. To the interpreter there is no difference between the two:

$ parse\_tree\_show -f  
‘a’ + stuff + ‘b’  
“a” + stuff + “b”  
“a#{stuff}b”  
(eval):1: warning: useless use of + in void context  
(eval):2: warning: useless use of + in void context  
[[:call,  
[:call, [:str, “a”], :+, [:array, [:vcall, :stuff]]],  
:+,  
[:array, [:str, “b”]]],  
[:call,  
[:call, [:str, “a”], :+, [:array, [:vcall, :stuff]]],  
:+,  
[:array, [:str, “b”]]],  
[:dstr, “a”, [:vcall, :stuff], [:str, “b”]]]

–  
Eric H. - removed\_email\_address@domain.invalid - [http://blog.segment7.net](http://blog.segment7.net)

I LIT YOUR GEM ON FIRE!