What's New in Ruby 2.0

Copyright (C) 2013 DeNA Co.,Ltd. All Rights Reserved.
What's New in Ruby 2.0
February 22nd, 2013.
URABE, Shyouhei.
PFSYS Dept., GPS Div.,
DeNA Co., Ltd.

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Ruby 2 is CoMING!
URABE, Shyouhei.
DeNA Co., Ltd.

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/people/@me/@self
●
@shyouhei
●
Ruby Core Team
●
Ruby 1.8.{5,6,7}
release mgr. &
branch mentor

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Delight and Impact the World

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Ruby 2.0.0 is coming
●
Ruby, version 2.0.0, is appearing in Feb. 24th,
2013. What's expected?
– More syntax
– More speed
– More feature
– … and maybe more!

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Ruby is Growing

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http://modulecounts.com

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Ruby and “Good Parts”
“Ruby is designed to be fun.”
– Yukihiro Matsumoto
出典 : 「オブジェクト指向スクリプト言語 Ruby 」

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“I was socked. Ruby was the frst language
emphasized on our feeling.”
– Dr. Shinichiro Hara
http://www.nicovideo.jp/watch/sm6516554

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“The real paradigm shift is in the fact that Ruby
was designed to make programming fast,
enjoyable and easy instead of being optimized
for machines running it.”
– Matt Aimonetti
http://merbist.com/2009/11/16/the-ruby-revolution-take-ii/

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What drives us
“I was delighted to refect on the thought that
they were right there in the values of Ward, Kent,
and all the other people who've been advocating
clean code, well-factored object-oriented design,
and testability. These ideas have made a great
impact on many other technological communi-
ties, but in Ruby-land they are the orthodoxy.”
– Martin Fowler
http://www.martinfowler.com/bliki/RailsConf2007.html

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What drives us
“Ruby doesn't change your company. It is you
who are changed. You are to change the world.”
– Shunichi Arai
広島 Ruby 会議 01 での発言

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Change

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Why Ruby 2.0
●
Because we change things.
●
We are eager to make ourself more and more
happy, healthy, productive.
●
Don't be afraid. “Embrace the change.”

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What's New in Ruby 2.0
URABE, Shyouhei.
DeNA Co., Ltd.

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What's NOT new in Ruby 2
●
Almost everything.
●
“100% backward compatible”, said matz.
– In reality …
●
(for instance) Rails runs as-is.

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That being said,
●
New things are added
●
Also lots of internal improvements

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New Syntax in Ruby 2.0
URABE, Shyouhei.
DeNA Co., Ltd.

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Keyword arguments
●
Following code was already OK since 1.x.
●
So, what's the problem?
obj.method "with", :lots => "of",
:args => "in",
:hash => "form"

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Keyword arguments
●
The problem is on method definition:
def obj.method(arg, hash)
lots = Hash[:lots] || "default"
args = Hash[:args] || "another"
hand = Hash[:by hand] || "annoying"
…
end Hand-written code
== root cause of bugs

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Keyword arguments
●
Introducing keyword args (since 2.0):
●
This way, local variables “a”, “b”, “c”, and “d”
are all assigned.
●
Caller side doesn't change.
def obj.method(a, b = 1, c: 1, d: 2)
Positional Optional Keyworded
Keyworded

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Other minor syntactic updates
●
Symbol array literal %i and %I introduced.
●
Ruby now thinks its inputs to be UTF-8
encoded by default. You can of course specify
other encodings explicitly.
%i(foo bar baz) # => [:foo, :bar, :baz]

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Ruby 2.0 improvements of
Core Performance
URABE, Shyouhei.
DeNA Co., Ltd.

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require improvements
●
Background: today as we have gems, booting
ruby up tends to require 128+ libraries at
once, resulting poor experience.
●
Solution: require got faster (in sense of com-
putational complexity).
– Several techniques to reduce computations.

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require improvements

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Backtrace lazy generation
●
Since the beginning, backtraces has been
arrays of strings.
●
Each time an exception was raised, these
strings were generated from up to down, even
when that was not actually used.
– Can get ultra slow when you have 1024+ stack
frames (typical Rails situation).

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●
Starting ruby 2.x, Thread::Backtrace are used
instead of strings.
– Which are very lightweight.
●
When you need to look at the backtrace, just
convert them to strings (call #to_s).

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Flonum introduced
●
On a 64bit machine (ubiquitous these days),
pointers, integers and foating-point numbers
are all 64bit width.
●
In ruby, pointers and integers are C level
register variables. But double was stored
on-memory. What if we can handle them like
pointers?

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Flonum introduced
fags
fags
klass
klass
double
double
(unused)
(unused)
(unused)
(unused)
double/ptr
double/ptr
struct
union

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Flonum introduced
●
Problem: how to union a pointer and a double?
MSB LSB
offset
PT
PD
PDP
PML4
(unused)
MSB LSB
fraction
exponent
sign

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Flonum introduced
●
Solution: some tricky bit-shifts
– Sasada, K., “A Lightweight Representation of
Floating-Point Numbers on Ruby Interpreter”, in
PPL2008.

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Benchmark results
0
0.5
1
1.5
2
2.5
3
app_answer
app_factorial
app_pentomino
app_tak
io_file_create
io_select
loop_for
loop_whileloop
so_array
so_count_words
so_fasta
so_mandelbrot
so_nbody
so_nsieve_bits
so_pidigits
so_sieve
vm1_block*
vm1_float_calc*
vm1_length*
vm1_lvar_set*
vm1_rescue*
vm2_array*
vm2_case*
vm2_method*
vm2_poly_method_ov*
vm2_raise2*
vm2_super*
vm3_backtrace
vm3_thread_mutex
vm_thread_mutex1
vm_thread_pass
clean/flonum
clean/flonum.z
© benchmarked by @_ko1

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GC things
●
Bitmap marking: GC mark bits were in every
objects, but moved into a dedicated memory
page to reduce cache misshits (also much
more CoW friendly).
●
Nonrecursive marking: mark function now
avoids the risk of machine stack overfow.
●
Lazy sweep (since 1.9.3): sweeper collects only
what's necessary (reduces stop time).

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Ruby 2.0 New Core Features
#1 Instrumentations
URABE, Shyouhei.
DeNA Co., Ltd.

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DTrace support!
●
You can probe live production Ruby behaviour
in non-stop, non-overhead fashion.
●
Supports Solaris (dtrace), Mac OS X (dtrace),
and Linux (SystemTrap).
● http://bugs.ruby-lang.org/projects/ruby/wiki/DTraceProbes

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DTrace support!
●
Mac example
MAC % sudo dtrace -q -n 'ruby$target:::find-require-entry {
printf("%s\n", copyinstr(arg0))
}' -c "ruby /var/apps/www/script/rails server"

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TracePoint
●
DTrace is great, but not ruby-way. I want to
programmatically dynamically trace some
execution!
●
Then use TracePoint.

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TracePoint
trace = TracePoint.new(:raise) do |tp|
p [tp.lineno, tp.event, tp.raised_exception]
end
#=> #
trace.enable
#=> #
0 / 0
#=> [5, :raise, #]

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GC stats
●
GC.stat: live object counts
●
GC::Profiler(1.9+): GC timing profiler
GC.stat #=> {
count: 17,
heap_used: 79,
heap_length: 79,
heap_increment: 0,
heap_live_num: 22798,
heap_free_num: 18020,
heap_final_num: 0,
total_allocated_object: 82397,
total_freed_object: 59599,
}

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Ruby 2.0 New Core Features
#2 Core Libraries
URABE, Shyouhei.
DeNA Co., Ltd.

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Fine-Grained Asynchronous Interrupt Handling
●
Background: ruby execution sometimes gets
interrupted for various reasons, e.g. timeout.
timeout(rand()) do
setup
handle
teardown
end
Complete Russian
Roulette on where
it gets interrupted!

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Thread.async_interrupt_timing Timeout::Error => :defer do
timeout(rand()) do
begin
Thread.async_interrupt_timing Timeout::Error => :immediate do
setup
handle
…
end
ensure
teardown
end
end
end

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Thread.async_interrupt_timing Timeout::Error => :defer do
timeout(rand()) do
begin
Thread.async_interrupt_timing Timeout::Error => :immediate do
setup
handle
…
end
ensure
teardown
end
end
end
Blue area gets
interrupted
Red area does not.

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Module Prepending
●
Sometimes you want to add setup / teardown
of a method defined elswhere.
module ActiveRecordHelper
def save
???
end
end
Wanna setup/teardown
but how do we do that?

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Module Prepending
module AR::Helper
def save
foo
super
baz
end
end
Foo.new.save
class Foo < AR::Base
prepend AR::Helper
def save
bar
end
end

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Module Prepending
●
This is how we solved Rails' “alias method
chain” situation. AMC is no longer needed.

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Lazy Enumerator
●
Ruby's foo.bar.baz. … style (so-called being
“fuent”) sometimes requires unnecessary
temporary object to pass around, which can
theoretically be avoided by lazy evaluations.

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Lazy Enumerator
File.open(path) {|fp|
fp.each_line. \
select {|line|
/regexp/ =~ line
}. \
each_with_index.map {|line, no|
sprintf("%d: %s\n", no, line)
}. \
first(10).each {|str|
puts(str)
}
}
Generates temporary array

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Lazy Enumerator
File.open(path) {|fp|
fp.each_line.lazy \
select {|line|
/regexp/ =~ line
}. \
each_with_index.map {|line, no|
sprintf("%d: %s\n", no, line)
}. \
first(10).each {|str|
puts(str)
}
}
No temporary array
No temporary array
No temporary array
Doesn't even read until EOF

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Lazy Enumerator
●
Interesting application: infinite enumerator
# Leibniz formula for π
(0..Float::INFINITY).lazy.map {|i|
((-1) ** i) / (2*i + 1).to_f
}.take(65536).reduce(:+) * 4

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Other new methods
●
Kernel.__dir__: directory name of __FILE__
●
Kernel#to_h: ubiquitous Hash conversion
●
Random class(1.9+): repeatable PRNG
●
IO#wait_writable: wait until it gets writable
●
Refinements: experimental.

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Standard Library updates
for Ruby 2.0
URABE, Shyouhei.
DeNA Co., Ltd.

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CGI
●
CGI is now HTML5 ready.

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net/http
●
Now supports SNI (Server Name Indication)

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Zlib binding
●
Zlib now runs out of the interpreter lock. This
means zlib runs faster than before on multi-
threaded situations.

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Updated stdlibs
●
Rubygems 2.0.0
●
JSON 1.7.7
●
Rake 0.9.5
●
Rdoc 4.0
●
And others (REXML, yaml, openssl, …)

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Conclusion

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What's NOT new in Ruby 2
●
Almost everything.
●
“100% backward compatible”, said matz.
●
(for instance) Rails runs as-is.
●
Don't be afraid! Just start using 2.0.0!

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That being said,
●
New things are added
●
Also lots of internal improvements
●
Even if you are already confident about your
current environment, 2.0.0 is worth looking at.

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Use Ruby Today!

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What's New in Ruby 2.0

What's New in Ruby 2.0

Urabe Shyouhei

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