dmke/README.md

## README.md

      
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              README.md
            
          
    Just a small benchmark to clear up the myth, Ruby wouldn'd garbage collect any Symbols. In fact, MRI 2.2.0 introduced Symbol GC in December 2014 (see notable changes in the release announcement).
The benchmark is quite simple: It basically cretes a bunch of Symbols via String#to_sym and counts Symbol::all_symbols afterwards.
I've used rbenv to test the Symbol GC (or the lack thereof) of these interpreter implementations:

1.9.3-p551
2.0.0-p645
2.1.6
2.2.2
rbx-2.5.5
jruby-1.7.20
jruby-9000-dev

To get the results by yourself, simply execute bench.rb in the interpreter of your choice.
Results

Engine: ruby, Version 1.9.3 (rbenv 1.9.3-p551)


1861 Symbols after boot
1001861 Symbols after generating 1000000
1001861 Symbols after GC'ing

Finished in 2.68s
Engine: ruby, Version 2.0.0 (rbenv 2.0.0-p645)


2298 Symbols after boot
1002298 Symbols after generating 1000000
1002298 Symbols after GC'ing

Finished in 2.34s
Engine: ruby, Version 2.1.6 (rbenv 2.1.6)


2418 Symbols after boot
1002418 Symbols after generating 1000000
1002418 Symbols after GC'ing

Finished in 2.29s
Engine: ruby, Version 2.2.2 (rbenv 2.2.2)


2524 Symbols after boot
2888 Symbols after generating 1000000
2524 Symbols after GC'ing

Finished in 1.76s
Engine: rbx, Version 2.1.0 (rbenv rbx-2.5.5)


8413 Symbols after boot
1008413 Symbols after generating 1000000
1008413 Symbols after GC'ing

Finished in 2.59s
Engine: jruby, Version 1.9.3 (rbenv jruby-1.7.20)


965 Symbols after boot
1000965 Symbols after generating 1000000
1000965 Symbols after GC'ing

Finished in 3.30s
Engine: jruby, Version 2.2.0 (rbenv jruby-9000-dev)


973 Symbols after boot
636418 Symbols after generating 1000000
636418 Symbols after GC'ing

Finished in 3.60s

  
## bench.rb
#!/usr/bin/env ruby

start = Time.now
N = (ARGV[0] || 1_000_000).to_i

def make_symbol(i)
  name = "symbol_%10d" % i
  name.to_sym
end

printf "## Engine: %s, Version %s (rbenv %s)\n\n", RUBY_ENGINE, RUBY_VERSION, ENV["RBENV_VERSION"]
printf "- `%d` Symbols after boot\n", Symbol.all_symbols.size

N.times {|i| make_symbol(i) }
printf "- `%d` Symbols after generating %d \n", Symbol.all_symbols.size, N

GC.start
printf "- `%d` Symbols after GC'ing\n\n", Symbol.all_symbols.size
printf "Finished in %.02fs\n\n", (Time.now - start)

## run.sh
#!/bin/sh

rubies="1.9.3-p551 2.0.0-p645 2.1.6 2.2.2 rbx-2.5.5 jruby-1.7.20 jruby-9000-dev"

for r in $rubies; do
  RBENV_VERSION=$r ruby ./bench.rb $*
done
	#!/usr/bin/env ruby

	start = Time.now
	N = (ARGV[0] \|\| 1_000_000).to_i

	def make_symbol(i)
	name = "symbol_%10d" % i
	name.to_sym
	end

	printf "## Engine: %s, Version %s (rbenv %s)\n\n", RUBY_ENGINE, RUBY_VERSION, ENV["RBENV_VERSION"]
	printf "- `%d` Symbols after boot\n", Symbol.all_symbols.size

	N.times {\|i\| make_symbol(i) }
	printf "- `%d` Symbols after generating %d \n", Symbol.all_symbols.size, N

	GC.start
	printf "- `%d` Symbols after GC'ing\n\n", Symbol.all_symbols.size
	printf "Finished in %.02fs\n\n", (Time.now - start)
	#!/bin/sh

	rubies="1.9.3-p551 2.0.0-p645 2.1.6 2.2.2 rbx-2.5.5 jruby-1.7.20 jruby-9000-dev"

	for r in $rubies; do
	RBENV_VERSION=$r ruby ./bench.rb $*
	done