# New Optimization idea **URL:** \ **Category:** Ruby\ **Created:** [March 27, 2006, 11:18pm UTC](https://www.ruby-forum.com/t/new-optimization-idea/56073 "2006-03-27T23:18:26Z")\ **Posts on this page:** 5\ **Page:** 1
**Author:** ![amin1426](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/4da419/32.png) [@amin1426](https://www.ruby-forum.com/u/amin1426)\ **Post date:** [March 27, 2006, 11:18pm UTC](https://www.ruby-forum.com/t/new-optimization-idea/56073/1 "2006-03-27T23:18:26Z")
I have a couple of classes like so… class Foo def step1 @mine = Hash.new # Perhaps stuff things into @mine end def step2 @mine.each\_pair do |key,value| # Do stuff end end end Profiling with my “new” profiler shows that I’m creating many many Hash objects, probably way more than I need. In fact most of them are empty. Optimization trick… class Object FROZEN\_EMPTY\_HASH = Hash.new.freeze end class Foo @@hash\_cache = Hash.new def step1 @mine = @@hash\_cache # Perhaps stuff things into @mine if @mine.empty? @mine = FROZEN\_EMPTY\_HASH else @@hash\_cache = Hash.new end end def step2 @mine.each\_pair do |key,value| # Do stuff end end end John C. Phone : (64)(3) 358 6639 Tait Electronics Fax : (64)(3) 359 4632 PO Box 1645 Christchurch Email : removed\_email\_address@domain.invalid New Zealand Carter’s Clarification of Murphy’s Law. “Things only ever go right so that they may go more spectacularly wrong later.” From this principle, all of life and physics may be deduced. ---
**Author:** ![amin1426](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/4da419/32.png) [@amin1426](https://www.ruby-forum.com/u/amin1426)\ **Post date:** [March 28, 2006, 9:00pm UTC](https://www.ruby-forum.com/t/new-optimization-idea/56073/2 "2006-03-28T21:00:10Z")
John C. wrote: > ``` > # Do stuff > > ``` > > class Object > @mine = FROZEN\_EMPTY\_HASH > end > You could as well leave the member nil and change the getter > appropriately: class Foo def mine() @mine || FROZEN\_EMPTY\_HASH end def step2() mine.each\_pair … end Or do the test in step2… @mine and @mine.each\_pair … Kind regards ``` robert ``` ---
**Author:** ![amin1426](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/4da419/32.png) [@amin1426](https://www.ruby-forum.com/u/amin1426)\ **Post date:** [March 28, 2006, 11:47pm UTC](https://www.ruby-forum.com/t/new-optimization-idea/56073/3 "2006-03-28T23:47:17Z")
On Wed, 29 Mar 2006, Robert K. wrote: > You could as well leave the member nil and change the getter appropriately: > > class Foo > def mine() @mine || FROZEN\_EMPTY\_HASH end > def step2() mine.each\_pair … > end > > Or do the test in step2… > @mine and @mine.each\_pair … I didn’t want to do that since @mine.each and .has\_key? was going to be evaluated often and in many places. ie. The optimization tweak would have been a shot gun hack all over the place. However, if anybody had listened to me about the Null Object pattern and nil… I wouldn’t have had to do anything. John C. Phone : (64)(3) 358 6639 Tait Electronics Fax : (64)(3) 359 4632 PO Box 1645 Christchurch Email : removed\_email\_address@domain.invalid New Zealand Carter’s Clarification of Murphy’s Law. “Things only ever go right so that they may go more spectacularly wrong later.” From this principle, all of life and physics may be deduced. ---
**Author:** ![amin1426](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/4da419/32.png) [@amin1426](https://www.ruby-forum.com/u/amin1426)\ **Post date:** [March 29, 2006, 11:54pm UTC](https://www.ruby-forum.com/t/new-optimization-idea/56073/4 "2006-03-29T23:54:35Z")
On Mar 27, 2006, at 1:18 PM, John C. wrote: > ``` > # Do stuff > end > > ``` > > end > end > > Profiling with my “new” profiler shows that I’m creating many many > Hash objects, probably way more than I need. In fact most of them > are empty. > > Optimization trick… Maybe it is just me, but I find your original code much easier to read and intuitive than your second version. There is just too much wonky-thought going on in the second version and it’ll make it easy to get it wrong (esp if this pattern spreads throughout a large code base). I don’t know what your real code is doing, but creating empty hashes seems fine to me. They don’t actually cost all that much: % time ruby -e ‘1\_000\_000.times do Hash.new; end’ real 0m7.107s user 0m3.432s sys 0m0.101s (with itunes running in the background no less) One suggestion I could make is to recycle if you really are making too many empty hashes. If you are running step1/2 in a loop and doing a lot of such work, only reinstantiate @mine if you need to: def initialize @mine = Hash.new end def step1 @mine = Hash.new unless @mine.empty? # … end That is only a teeny change to your original logic and meets your goals of creating less hashes. I can read that and grok the intent immediately. I can’t with your rewrite. – \_why: zenspider’s most intense moments of solice are immediately following the slaughter […] \_why: that topknot’s the only thing keeping a lid on the righteous anger bricolage: yeah, that and his flagrant obsession with dvorak ---
**Author:** ![amin1426](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/4da419/32.png) [@amin1426](https://www.ruby-forum.com/u/amin1426)\ **Post date:** [March 31, 2006, 8:32am UTC](https://www.ruby-forum.com/t/new-optimization-idea/56073/5 "2006-03-31T08:32:36Z")
On Thu, 30 Mar 2006, Ryan D. wrote: > Maybe it is just me, but I find your original code much easier to read and > intuitive than your second version. There is just too much wonky-thought > going on in the second version and it’ll make it easy to get it wrong (esp if Like any optimization, premature, it’s the root of all programming evil. In my case profiling showed up a case where I was starting to consume significant non-GC’able memory resources which were slowing the system as a whole. In this case it was worth it. In general, no. John C. Phone : (64)(3) 358 6639 Tait Electronics Fax : (64)(3) 359 4632 PO Box 1645 Christchurch Email : removed\_email\_address@domain.invalid New Zealand Carter’s Clarification of Murphy’s Law. “Things only ever go right so that they may go more spectacularly wrong later.” From this principle, all of life and physics may be deduced.