Rationalは有理数を表すRubyクラス。Ruby1.0の頃から存在する歴史あるクラスだが、1.9から組み込みクラスになり、1.9.2からはTimeの内部表現の一つとして採用され、2.1からはリテラル表記が導入されるなど、その重要性は近年それなりに高まり続けている。 しかし現状のRationalは、不必要に遅い実装になっている。現状のRationalがなぜ遅いのか、それをどうやって速くしようとしているのか、今年度Ruby開発プロジェクト助成金の対象者として、その技術的な概要を述べる。 また、話者がなぜRationalに目を付け、その最適化を試みているのかについても話す。 Moved from: https://niconare.nicovideo.jp/watch/kn856

1. Rationalを
最適化してみた
斎藤ただし
Tadashi Saito

2. 2 topics

3. ① How to optimize
Rational
②Let's read CRuby
source code more!

4. ① How to optimize
Rational
②Let's read CRuby
source code more!

5. Rational

6. Rational
Number
Library

7. 1
2
+
2
3
=?

8. Can't
express with
Float

9. Can't
express with
BigDecimal

10. Rational

11. 1/2r + 2/3r

12. 1/2r + 2/3r
#=> (7/6)

13. Direct
results

14. Exists since
Ruby 1.0

15. Ruby 1.9
Built-in class

16. Ruby 1.9.2
Internal
representa-
tion of Time

17. Ruby 2.1
Literal
（1/2r）

18. More
important in
recent years

19. It's not so
fast

20. rb_funcall()

21. Ruby-level
method calling
in C extention

22. Porting speed?
Too lazy to impl
polymorphic in C?

23. Ruby-level
method calling
still exists

24. Profile with
prof(1)

25. rb_funcall()
consumes
big time

26. Let's substitute
it with only C-
layer calculation

27. Ruby
Association
grant project
submit
http://www.ruby.or.jp/ja/news/20150803.html

28. Ruby
Association
grant project
adopted!!1
http://www.ruby.or.jp/ja/news/20151116.html

29. ●
2015-10-30 Notification of result
●
2016-1-4 intermediate reports
●
2016-3-4 final reports

30. ●
2015-10-30 Notification of result
← HERE! #ragrant2015
●
2016-1-4 intermediate reports
●
2016-3-4 final reports

31. How long was
faster?
(ongoing)

32. 0.000
0.500
1.000
1.500
2.000
2.500
3.000
3.500
4.000

33. + fixnum + bignum - fixnum - bignum
0.000
0.500
1.000
1.500
2.000
2.500
3.000
3.500
4.000

34. x 3

35. Matz
"Ruby 3x3"

36. Rational (only)
3.0!!1

37. Currently
finished only
four arithmetic
operations

38. I will do my
best also
rest
github.com/tadd/ruby/commits/ragrant2015development

39. ① How to optimize
Rational
②Let's read CRuby
source code more!

40. I was reading
somehow
from the
usual

41. I don't have
enough
expertise

42. rb_funcall()

43. “It's
different from
others”

44. Read source
code somehow
from the usual

45. Ruby Hacking
Guide
http://i.loveruby.net/ja/rhg/book/

46. is little
difficult

47. Built-in
class
libraries

48. Clear purpose
Independent
Could write in
Ruby

49. Low cost to
learn

50. compar.c

51. 230 lines
6 methods
50 commits in
17 years

52. After
troubled:
doc/extension.ja.rdoc

53. Only for
extension
libraries?

54. Ruby
internal uses
same API too

55. You'll be
able to read
it somehow

56. Find your
interest points
based on their
file names

57. Then you'll
find
contributable
points

58. ① How to optimize
Rational
②Let's read CRuby
source code more!

59. Another three
months, I'll try
to optimize
Rational
github.com/tadd/ruby/commits/ragrant2015development