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Introduce a benchmark template [ci skip] 

This replaces boilerplate in the “benchmark your code” section of the
contributors’ guide with an executable template. I also amended the text
to encourage best practices and codified it in the template.

For now this is only good for relatively self-contained changes that can
be inlined into a simple script. In the future, this can be expanded to
cover how to measure the difference between two commits.

The output looks like this:

```
==================================== Empty =====================================

Warming up --------------------------------------
              blank?   225.963k i/100ms
         fast_blank?   238.147k i/100ms
Calculating -------------------------------------
              blank?      8.825M (± 6.4%) i/s -     44.063M in   5.014824s
         fast_blank?      9.311M (± 6.3%) i/s -     46.439M in   5.009153s

Comparison:
         fast_blank?:  9310694.8 i/s
              blank?:  8824801.7 i/s - same-ish: difference falls within error


================================= Single Space =================================

Warming up --------------------------------------
              blank?    56.581k i/100ms
         fast_blank?   232.774k i/100ms
Calculating -------------------------------------
              blank?    813.985k (±16.7%) i/s -      4.017M in   5.076576s
         fast_blank?      9.547M (± 5.2%) i/s -     47.719M in   5.013204s

Comparison:
         fast_blank?:  9547414.0 i/s
              blank?:   813985.0 i/s - 11.73x  slower


================================== Two Spaces ==================================

Warming up --------------------------------------
              blank?    58.265k i/100ms
         fast_blank?   244.056k i/100ms
Calculating -------------------------------------
              blank?    823.343k (±16.2%) i/s -      4.020M in   5.014213s
         fast_blank?      9.484M (± 4.9%) i/s -     47.347M in   5.005339s

Comparison:
         fast_blank?:  9484021.6 i/s
              blank?:   823343.1 i/s - 11.52x  slower


=============================== Mixed Whitspaces ===============================

Warming up --------------------------------------
              blank?    53.919k i/100ms
         fast_blank?   237.103k i/100ms
Calculating -------------------------------------
              blank?    763.435k (±16.8%) i/s -      3.720M in   5.018029s
         fast_blank?      9.672M (± 5.8%) i/s -     48.369M in   5.019356s

Comparison:
         fast_blank?:  9672467.2 i/s
              blank?:   763435.4 i/s - 12.67x  slower


=============================== Very Long String ===============================

Warming up --------------------------------------
              blank?    34.037k i/100ms
         fast_blank?   240.366k i/100ms
Calculating -------------------------------------
              blank?    409.731k (± 8.9%) i/s -      2.042M in   5.028235s
         fast_blank?      9.794M (± 4.3%) i/s -     49.035M in   5.016328s

Comparison:
         fast_blank?:  9794225.2 i/s
              blank?:   409731.4 i/s - 23.90x  slower
```
This commit is contained in:
Godfrey Chan 2016-10-15 12:27:18 +02:00
parent 77ed6b782a
commit f2f9b88685
2 changed files with 65 additions and 25 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

49
guides/bug_report_templates/benchmark.rb Normal file
View File

@ -0,0 +1,49 @@
begin
require "bundler/inline"
rescue LoadError => e
$stderr.puts "Bundler version 1.10 or later is required. Please update your Bundler"
raise e
end
gemfile(true) do
source "https://rubygems.org"
gem "rails", github: "rails/rails"
gem "benchmark-ips"
end
require "active_support"
require "active_support/core_ext/object/blank"
# Your patch goes here.
class String
def fast_blank?
true
end
end
# Enumerate some representative scenarios here.
#
# It is very easy to make an optimization that improves performance for a
# specific scenario you care about but regresses on other common cases.
# Therefore, you should test your change against a list of representative
# scenarios. Ideally, they should be based on real-world scenarios extracted
# from production applications.
SCENARIOS = {
"Empty" => "",
"Single Space" => " ",
"Two Spaces" => " ",
"Mixed Whitspaces" => " \t\r\n",
"Very Long String" => " " * 100
}
SCENARIOS.each_pair do |name, value|
puts
puts " #{name} ".center(80, "=")
puts
Benchmark.ips do |x|
x.report('blank?') { value.blank? }
x.report('fast_blank?') { value.fast_blank? }
x.compare!
end
end

41
guides/source/contributing_to_ruby_on_rails.md
View File

@ -270,33 +270,24 @@ The above are guidelines - please use your best judgment in using them.
### Benchmark Your Code
If your change has an impact on the performance of Rails, please use the
[benchmark-ips](https://github.com/evanphx/benchmark-ips) gem to provide
benchmark results for comparison.
For changes that might have an impact on performance, please benchmark your
code and measure the impact. Please share the benchmark script you used as well
as the results. You should consider including these information in your commit
message, which allows future contributors to easily verify your findings and
determine if they are still relevant. (For example, future optimizations in the
Ruby VM might render certain optimizations unnecessary.)
Here's an example of using benchmark-ips:
It is very easy to make an optimization that improves performance for a
specific scenario you care about but regresses on other common cases.
Therefore, you should test your change against a list of representative
scenarios. Ideally, they should be based on real-world scenarios extracted
from production applications.
```ruby
require 'benchmark/ips'
Benchmark.ips do |x|
x.report('addition') { 1 + 2 }
x.report('addition with send') { 1.send(:+, 2) }
end
```
This will generate a report with the following information:
```
Calculating -------------------------------------
addition 132.013k i/100ms
addition with send 125.413k i/100ms
-------------------------------------------------
addition 9.677M (± 1.7%) i/s - 48.449M
addition with send 6.794M (± 1.1%) i/s - 33.987M
```
Please see the benchmark/ips [README](https://github.com/evanphx/benchmark-ips/blob/master/README.md) for more information.
You can use the [benchmark template](https://github.com/rails/rails/blob/master/guides/bug_report_templates/benchmark.rb)
as a starting point. It includes the boilerplate code to setup a benchmark
using the [benchmark-ips](https://github.com/evanphx/benchmark-ips) gem. The
template is designed for testing relatively self-contained changes that can be
inlined into the script.
### Running Tests