Posted by tobi — 11:49 AM Apr 03
ActiveSupport has this really nice returning tool. It allows you to rewrite the common pattern of initialization and returning a object from am method like this:
returning something = Thing.new do something.this something.that end
We were wondering if there may be a performance issue with the tool so a quick benchmark showed the following:
user system total real
def n; i = 0; return i; end 0.510000 0.000000 0.510000 ( 0.520417)
def n; i = 0; i ; end 0.340000 0.000000 0.340000 ( 0.344569)
def n; returning i = 0 do; end; end 0.730000 0.000000 0.730000 ( 0.726853)
Those numbers are after 1m runs on a core 2 duo laptop. As you can see the difference is very minor. Code vanity can safely prevail. Full Benchmark
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Pete Forde 03 Apr 12:38
I had no idea that returning existed! Thanks for the tip.
My question is why specifying return i is 40% slower?
Hongli Lai 03 Apr 13:00
Pete: It’s because of function call overhead. There’s nothing that can be done about that (except making it a full language construct, but that’s overkill).
Jay Fields 03 Apr 14:12
I’ve never seen returning used that way, I always use.
returning Thing.new do |thing| thing.this thing.that end
I guess it works either way.
tobias Lütke 03 Apr 15:33
Jay: Block variable or no block doesn’t seem to impact performance.
I personally think that the example in the post looks more natural, more like build in syntax but that’s definitely a taste thing.
rick 03 Apr 15:54
Ruby 1.9 has tap.
Thing.new.tap { |t| t.this }
Of course, some objects like ActiveRecord models already take a block:
Thing.new { |t| t.this = that }
Zbo 03 Apr 17:12
2x slower is a minor difference?
Neeraj 03 Apr 22:05
I couldn’t find returning declared in ActiveSupport. Does anyone have a link to it?
I thought returning was a creature of “facets”. http://facets.rubyforge.org/quick/rdoc/core/classes/Kernel.html#M000374
Sb 04 Apr 05:48
Zbo, agreed! How is 100% slower a “very minor” performance hit?
tobi 06 Apr 01:43
100% in an application which does nothing but return data. Even in the simplest of apps this would be totally negligible. Notice that this was 1m invocations performed in sub second.