# Why was the object\_id for true and nil changed in ruby2.0? **URL:** \ **Category:** ruby-talk\ **Created:** [20 March 2013 05:47 UTC](https://rubytalk.org/t/why-was-the-object-id-for-true-and-nil-changed-in-ruby2-0/67557 "2013-03-20T05:47:08Z")\ **Posts on this page:** 11\ **Page:** 1
**Author:** ![7stud2](https://avatars.discourse-cdn.com/v4/letter/7/9de053/32.png) [@7stud2](https://rubytalk.org/u/7stud2)\ **Post date:** [20 March 2013 05:47 UTC](https://rubytalk.org/t/why-was-the-object-id-for-true-and-nil-changed-in-ruby2-0/67557/1 "2013-03-20T05:47:08Z")
irb(main):001:0\> true.object\_id =\> 20 irb(main):002:0\> false.object\_id =\> 0 irb(main):003:0\> nil.object\_id =\> 8 The values for true and nil were respectively 2, 4 in 1.9.3 and 1.8.7, but have been changed to 20, 8 in ruby2.0.0 - even though the id of false remains the same i.e. 0 and the ids for Fixnum maintains the same old 2n+1 pattern. What's the reason behind this object\_id change? Why was this change made? How is this going to help developers? The full question can be seen here: > thanks! > **···** > > -- > Posted via [http://www.ruby-forum.com/](http://www.ruby-forum.com/). ---
**Author:** ![7stud2](https://avatars.discourse-cdn.com/v4/letter/7/9de053/32.png) [@7stud2](https://rubytalk.org/u/7stud2)\ **Post date:** [20 March 2013 06:03 UTC](https://rubytalk.org/t/why-was-the-object-id-for-true-and-nil-changed-in-ruby2-0/67557/2 "2013-03-20T06:03:43Z")
your question was already answered at stackoverflow: > > Seems to be something to do with “flonums” – a technique for speeding up floating point calculations on 64-bit: github.com/ruby/ruby/blob/v2\_0\_0\_0/include/ruby/ruby.h#L383-431 and ruby-forum.com/topic/4404164. > **···** > > -- > Posted via [http://www.ruby-forum.com/\](http://www.ruby-forum.com/%5C). ---
**Author:** ![7stud2](https://avatars.discourse-cdn.com/v4/letter/7/9de053/32.png) [@7stud2](https://rubytalk.org/u/7stud2)\ **Post date:** [20 March 2013 14:23 UTC](https://rubytalk.org/t/why-was-the-object-id-for-true-and-nil-changed-in-ruby2-0/67557/3 "2013-03-20T14:23:11Z")
hm the forumtopic i linked was in english ... hm okay, Flonums may be not the reason because they are only in 2.1dev   a = 1.1 + 1.2   b = 1.1 + 1.2   p(a.object\_id == b.object\_id) this shows true on 2.1, its false on 2.0p0 > **···** > > -- > Posted via [http://www.ruby-forum.com/](http://www.ruby-forum.com/). ---
**Author:** ![7stud2](https://avatars.discourse-cdn.com/v4/letter/7/9de053/32.png) [@7stud2](https://rubytalk.org/u/7stud2)\ **Post date:** [20 March 2013 16:35 UTC](https://rubytalk.org/t/why-was-the-object-id-for-true-and-nil-changed-in-ruby2-0/67557/4 "2013-03-20T16:35:31Z")
Well, there is a new answer on Stack Overflow. Gentlemen over here might want to take a look: > Seems legit... but I am not sure how can something like this lead to better perfomance? Any comments? > **···** > > -- > Posted via [http://www.ruby-forum.com/](http://www.ruby-forum.com/). ---
**Author:** ![7stud2](https://avatars.discourse-cdn.com/v4/letter/7/9de053/32.png) [@7stud2](https://rubytalk.org/u/7stud2)\ **Post date:** [20 March 2013 14:10 UTC](https://rubytalk.org/t/why-was-the-object-id-for-true-and-nil-changed-in-ruby2-0/67557/5 "2013-03-20T14:10:20Z")
Hans Mackowiak wrote in post #1102392: > your question was already answered at stackoverflow: > > > > Seems to be something to do with “flonums” – a technique for speeding up > > floating point calculations on 64-bit: > github.com/ruby/ruby/blob/v2\_0\_0\_0/include/ruby/ruby.h#L383-431 and > ruby-forum.com/topic/4404164. I have tried to read it, but the presentations given in that link are written in Japanese, and I couldn't understand what Flonums are why they are implemented. Know any place where I can read them in English to understand why it was changed? > **···** > > -- > Posted via [http://www.ruby-forum.com/\](http://www.ruby-forum.com/%5C). ---
**Author:** ![7stud2](https://avatars.discourse-cdn.com/v4/letter/7/9de053/32.png) [@7stud2](https://rubytalk.org/u/7stud2)\ **Post date:** [20 March 2013 16:22 UTC](https://rubytalk.org/t/why-was-the-object-id-for-true-and-nil-changed-in-ruby2-0/67557/6 "2013-03-20T16:22:57Z")
Hans Mackowiak wrote in post #1102451: > hm okay, Flonums may be not the reason because they are only in 2.1dev > >   a = 1.1 + 1.2 >   b = 1.1 + 1.2 >   p(a.object\_id == b.object\_id) > > this shows true on 2.1, its false on 2.0p0 This shows true in my system too, but my ruby -v is ruby 2.0.0p0 (2013-02-24 revision 39474) [x86\_64-linux], not 2.1. > **···** > > -- > Posted via [http://www.ruby-forum.com/\](http://www.ruby-forum.com/%5C). ---
**Author:** ![Matthew\_Kerwin](https://yyz1.discourse-cdn.com/flex029/user_avatar/rubytalk.org/matthew_kerwin/32/1845_2.png) [@Matthew\_Kerwin](https://rubytalk.org/u/Matthew_Kerwin)\ **Post date:** [20 March 2013 19:44 UTC](https://rubytalk.org/t/why-was-the-object-id-for-true-and-nil-changed-in-ruby2-0/67557/7 "2013-03-20T19:44:33Z")
Because immediate values have no overhead. It takes memory and cpu cycles to create an object instance; it takes no (extra) memory if the value is stored in the reference (ie the object id \_is\_ the value, albeit slightly modified), and far fewer cycles to shift and OR some bits. > **···** > > Sent from my phone, so excuse the typos. ---
**Author:** ![D\_Deryl\_Downey](https://avatars.discourse-cdn.com/v4/letter/d/8baadc/32.png) [@D\_Deryl\_Downey](https://rubytalk.org/u/D_Deryl_Downey)\ **Post date:** [20 March 2013 14:27 UTC](https://rubytalk.org/t/why-was-the-object-id-for-true-and-nil-changed-in-ruby2-0/67557/8 "2013-03-20T14:27:16Z")
ruby-forum.com/topic/4404164 specifically states why it was changed. Its a speed thing. ![](https://canada1.discourse-cdn.com/flex029/uploads/rubytalk/original/2X/0/02fa11a3de1fe32605e858d84f3b1dcef2045483.jpg) > **···** > > > Bharadwaj Srigiriraju \ > > March 20, 2013 10:10 AM > > > > I have tried to read it, but the presentations given in that link are > > written in Japanese, and I couldn't understand what Flonums are why they > > are implemented. > > > > Know any place where I can read them in English to understand why it was > > changed? > > > > Hans Mackowiak \ > > March 20, 2013 2:03 AM > > floating point calculations on 64-bit: > > github.com/ruby/ruby/blob/v2\_0\_0\_0/include/ruby/ruby.h#L383-431 and > > ruby-forum.com/topic/4404164. > > -- > D. Deryl Downey > >   "The bug which you would fright me with I seek" - William Shakespeare - The Winter's Tale, Act III, Scene II - A court of Justice. ---
**Author:** ![11142](https://avatars.discourse-cdn.com/v4/letter/1/e0b2c6/32.png) [@11142](https://rubytalk.org/u/11142)\ **Post date:** [20 March 2013 16:28 UTC](https://rubytalk.org/t/why-was-the-object-id-for-true-and-nil-changed-in-ruby2-0/67557/9 "2013-03-20T16:28:13Z")
This only should be true on 64bit Ruby 2.0. > **···** > > On Wed, 20 Mar 2013 17:22:57 +0100, Bharadwaj Srigiriraju \ wrote: > > > Hans Mackowiak wrote in post #1102451: > > > > > hm okay, Flonums may be not the reason because they are only in 2.1dev > > > > > >   a = 1.1 + 1.2 > > >   b = 1.1 + 1.2 > > >   p(a.object\_id == b.object\_id) > > > > > > this shows true on 2.1, its false on 2.0p0 > > > > This shows true in my system too, but my ruby -v is ruby 2.0.0p0 > > (2013-02-24 revision 39474) [x86\_64-linux], not 2.1. > > -- > Matma Rex ---
**Author:** ![Adam\_Prescott](https://avatars.discourse-cdn.com/v4/letter/a/7feea3/32.png) [@Adam\_Prescott](https://rubytalk.org/u/Adam_Prescott)\ **Post date:** [20 March 2013 14:38 UTC](https://rubytalk.org/t/why-was-the-object-id-for-true-and-nil-changed-in-ruby2-0/67557/10 "2013-03-20T14:38:20Z")
I'm interested (as is Hans, I think) in understanding the specifics of the implementation and \_why\_ this leads to better performance. Looks like someone would have to translate the Japanese, though. > **···** > > On 20 March 2013 14:27, D. Deryl Downey \ wrote: > > > ruby-forum.com/topic/4404164 specifically states why it was changed. Its a speed thing. ---
**Author:** ![7stud2](https://avatars.discourse-cdn.com/v4/letter/7/9de053/32.png) [@7stud2](https://rubytalk.org/u/7stud2)\ **Post date:** [20 March 2013 16:31 UTC](https://rubytalk.org/t/why-was-the-object-id-for-true-and-nil-changed-in-ruby2-0/67557/11 "2013-03-20T16:31:23Z")
Bartosz Dziewoński wrote in post #1102469: > **···** > > > On Wed, 20 Mar 2013 17:22:57 +0100, Bharadwaj Srigiriraju \> \ wrote: > > > > > (2013-02-24 revision 39474) [x86\_64-linux], not 2.1. > > > > This only should be true on 64bit Ruby 2.0. > > Yes. > > On 32 bit systems the object\_id didn't change at all. > > -- > Posted via [http://www.ruby-forum.com/\](http://www.ruby-forum.com/%5C).