Issue #13587 has been updated by k0kubun (Takashi Kokubun).
Status changed from Open to Closed
Assignee set to nobu (Nobuyoshi Nakada)
This was applied in r60320.
----------------------------------------
Feature #13587: Improve performance of string interpolation
https://bugs.ruby-lang.org/issues/13587#change-69389
* Author: south37 (Nao Minami)
* Status: Closed
* Priority: Normal
* Assignee: nobu (Nobuyoshi Nakada)
* Target version:
----------------------------------------
This patch will add pre-allocation in string interpolation.
By this, unnecessary capacity resizing is avoided.
For small strings, optimized `rb_str_resurrect` operation is faster, so pre-allocation is done only when concatenated strings are large.
`MIN_PRE_ALLOC_SIZE` was decided by experimenting with local machine (x86_64-apple-darwin 16.5.0, Apple LLVM version 8.1.0 (clang - 802.0.42)).
String interpolation will be faster around 72% when large string is created.
**Before**
```
Calculating -------------------------------------
Large string interpolation
1.276M (¡Þ 5.9%) i/s - 6.358M in 5.002022s
Small string interpolation
5.156M (¡Þ 5.5%) i/s - 25.728M in 5.005731s
```
**After**
```
Calculating -------------------------------------
Large string interpolation
2.201M (¡Þ 5.8%) i/s - 11.063M in 5.043724s
Small string interpolation
5.192M (¡Þ 5.7%) i/s - 25.971M in 5.020516s
```
**Test code**
```
require 'benchmark/ips'
Benchmark.ips do |x|
x.report "Large string interpolation" do |t|
a = "Hellooooooooooooooooooooooooooooooooooooooooooooooooooo"
b = "Wooooooooooooooooooooooooooooooooooooooooooooooooooorld"
t.times do
"#{a}, #{b}!"
end
end
x.report "Small string interpolation" do |t|
a = "Hello"
b = "World"
t.times do
"#{a}, #{b}!"
end
end
end
```
**Patch**
https://github.com/ruby/ruby/pull/1626
--
https://bugs.ruby-lang.org/
Unsubscribe: <mailto:ruby-core-request / ruby-lang.org?subject=unsubscribe>
<http://lists.ruby-lang.org/cgi-bin/mailman/options/ruby-core>