Erwin
2011-Mar-12 10:10 UTC
[RUBY] how do generate a random number w specific distribution ( which library ?)
I know how to generate a random number between 1 and 2 : def random return (1 + rand(2)) end but let''s say I would like to return 1 in 80% of the calls and 2 in 20% of the call... which library should I use ? ( I''ve seen a lot at http://raa.ruby-lang.org/ ) thanks for your suggestions -- You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org To unsubscribe from this group, send email to rubyonrails-talk+unsubscribe-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en.
Colin Law
2011-Mar-12 10:37 UTC
Re: [RUBY] how do generate a random number w specific distribution ( which library ?)
On 12 March 2011 10:10, Erwin <yves_dufour-ee4meeAH724@public.gmane.org> wrote:> I know how to generate a random number between 1 and 2 : > > def random > return (1 + rand(2)) > end > > but let''s say I would like to return 1 in 80% of the calls and 2 in > 20% of the call... > which library should I use ? ( I''ve seen a lot at http://raa.ruby-lang.org/ > ) >No doubt there are better ways but something like (rand(100) + 120)/100 should do it. Colin -- You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org To unsubscribe from this group, send email to rubyonrails-talk+unsubscribe@googlegroups.com. For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en.
Rob Biedenharn
2011-Mar-12 13:42 UTC
Re: [RUBY] how do generate a random number w specific distribution ( which library ?)
On Mar 12, 2011, at 5:37 AM, Colin Law wrote:> On 12 March 2011 10:10, Erwin <yves_dufour-ee4meeAH724@public.gmane.org> wrote: >> I know how to generate a random number between 1 and 2 : >> >> def random >> return (1 + rand(2)) >> end >> >> but let''s say I would like to return 1 in 80% of the calls and 2 in >> 20% of the call... >> which library should I use ? ( I''ve seen a lot at http://raa.ruby-lang.org/ >> ) >> > > No doubt there are better ways but something like > (rand(100) + 120)/100 > should do it. > > ColinWell, perhaps something that reveals the intention better: def usually_one rand < 0.80 ? 1 : 2 end -Rob Rob Biedenharn Rob-xa9cJyRlE0mWcWVYNo9pwxS2lgjeYSpx@public.gmane.org http://AgileConsultingLLC.com/ rab-/VpnD74mH8+00s0LW7PaslaTQe2KTcn/@public.gmane.org http://GaslightSoftware.com/ -- You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org To unsubscribe from this group, send email to rubyonrails-talk+unsubscribe-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en.
Colin Law
2011-Mar-12 14:23 UTC
Re: [RUBY] how do generate a random number w specific distribution ( which library ?)
On 12 March 2011 13:42, Rob Biedenharn <Rob-GBZH0y1GwQfnZcttdmLDtcI/UQi/AW5J@public.gmane.org> wrote:> > On Mar 12, 2011, at 5:37 AM, Colin Law wrote: > >> On 12 March 2011 10:10, Erwin <yves_dufour-ee4meeAH724@public.gmane.org> wrote: >>> >>> I know how to generate a random number between 1 and 2 : >>> >>> def random >>> return (1 + rand(2))No it doesn''t actually. 1 + rand would be better, though it depends what you mean by *between* whether even that is correct.>>> end >>> >>> but let''s say I would like to return 1 in 80% of the calls and 2 in >>> 20% of the call... >>> which library should I use ? ( I''ve seen a lot at >>> http://raa.ruby-lang.org/ >>> ) >>> >> >> No doubt there are better ways but something like >> (rand(100) + 120)/100 >> should do it. >> >> Colin > > > Well, perhaps something that reveals the intention better: > > def usually_one > rand < 0.80 ? 1 : 2 > endYes, much better. I suppose it is the old programmer in me instinctively avoiding floating point to save on processor time. A bit silly when everything has hardware floating point. Colin -- You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org To unsubscribe from this group, send email to rubyonrails-talk+unsubscribe@googlegroups.com. For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en.
Michael Pavling
2011-Mar-12 20:47 UTC
Re: [RUBY] how do generate a random number w specific distribution ( which library ?)
On 12 March 2011 14:23, Colin Law <clanlaw-gM/Ye1E23mwN+BqQ9rBEUg@public.gmane.org> wrote:> On 12 March 2011 13:42, Rob Biedenharn <Rob-GBZH0y1GwQfnZcttdmLDtcI/UQi/AW5J@public.gmane.org> wrote: >> def usually_one >> rand < 0.80 ? 1 : 2 >> end > > Yes, much better. I suppose it is the old programmer in me > instinctively avoiding floating point to save on processor time. A > bit silly when everything has hardware floating point.Although I prefer Rob''s suggestion as a better example of self documented code; this is another alternative... def usually_one [1,2,2,2,2][rand(5)] end ...there''s many ways to skin a cat :-) -- You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org To unsubscribe from this group, send email to rubyonrails-talk+unsubscribe@googlegroups.com. For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en.
Michael Pavling
2011-Mar-12 20:48 UTC
Re: [RUBY] how do generate a random number w specific distribution ( which library ?)
On 12 March 2011 20:47, Michael Pavling <pavling-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:> def usually_one > [1,2,2,2,2][rand(5)] > end*ahem* of course.. this is the total opposite of what the OP asked for, and returns 1 in 20% of the calls :-D sorry for not paying attention.... oops! -- You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org To unsubscribe from this group, send email to rubyonrails-talk+unsubscribe@googlegroups.com. For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en.
Colin Law
2011-Mar-12 21:07 UTC
Re: [RUBY] how do generate a random number w specific distribution ( which library ?)
On 12 March 2011 20:47, Michael Pavling <pavling-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:> On 12 March 2011 14:23, Colin Law <clanlaw-gM/Ye1E23mwN+BqQ9rBEUg@public.gmane.org> wrote: >> On 12 March 2011 13:42, Rob Biedenharn <Rob-GBZH0y1GwQfnZcttdmLDtcI/UQi/AW5J@public.gmane.org> wrote: >>> def usually_one >>> rand < 0.80 ? 1 : 2 >>> end >> >> Yes, much better. I suppose it is the old programmer in me >> instinctively avoiding floating point to save on processor time. A >> bit silly when everything has hardware floating point. > > Although I prefer Rob''s suggestion as a better example of self > documented code; this is another alternative... > > def usually_one > [1,2,2,2,2][rand(5)] > end >Ha! Vindicated ruby-1.8.7-p302 > begin ruby-1.8.7-p302 > t=Time.now ruby-1.8.7-p302 ?> 1000000.times{(rand(100) + 120)/100} ruby-1.8.7-p302 ?> puts Time.now-t ruby-1.8.7-p302 ?> end 0.905431 ruby-1.8.7-p302 > begin ruby-1.8.7-p302 > t=Time.now ruby-1.8.7-p302 ?> 1000000.times{rand < 0.80 ? 1 : 2} ruby-1.8.7-p302 ?> puts Time.now-t ruby-1.8.7-p302 ?> end 1.712769 ruby-1.8.7-p302 > begin ruby-1.8.7-p302 > t=Time.now ruby-1.8.7-p302 ?> 1000000.times{ [1,2,2,2,2][rand(5)] } ruby-1.8.7-p302 ?> puts Time.now-t ruby-1.8.7-p302 ?> end 1.150481> ...there''s many ways to skin a cat :-)But how fast can you do it? Colin -- You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org To unsubscribe from this group, send email to rubyonrails-talk+unsubscribe@googlegroups.com. For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en.
Michael Pavling
2011-Mar-12 21:36 UTC
Re: [RUBY] how do generate a random number w specific distribution ( which library ?)
On 12 March 2011 21:07, Colin Law <clanlaw-gM/Ye1E23mwN+BqQ9rBEUg@public.gmane.org> wrote:> Ha! VindicatedI expected to get different times, but to keep the proportions the same... but I get a little difference in order of speed:>> begin?> t=Time.now>> 1000000.times{(rand(100) + 120)/100} >> puts Time.now-t >> end1.200484>> begin?> t=Time.now>> 1000000.times{rand < 0.80 ? 1 : 2} >> puts Time.now-t >> end1.249109>> begin?> t=Time.now>> 1000000.times{[1,2,2,2,2][rand(5)]} >> puts Time.now-t >> end1.498434>> ...there''s many ways to skin a cat :-) > > But how fast can you do it?A fair bit faster if I don''t build the array in every loop ;-)>> x=[1,2,2,2,2]=> [1, 2, 2, 2, 2]>> begin?> t=Time.now>> 1000000.times{x[rand(5)]} >> puts Time.now-t >> end1.026202 -- You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org To unsubscribe from this group, send email to rubyonrails-talk+unsubscribe@googlegroups.com. For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en.
Colin Law
2011-Mar-12 22:01 UTC
Re: [RUBY] how do generate a random number w specific distribution ( which library ?)
On 12 March 2011 21:36, Michael Pavling <pavling-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:> On 12 March 2011 21:07, Colin Law <clanlaw-gM/Ye1E23mwN+BqQ9rBEUg@public.gmane.org> wrote: >> Ha! Vindicated > > I expected to get different times, but to keep the proportions the > same... but I get a little difference in order of speed: > >>> begin > ?> t=Time.now >>> 1000000.times{(rand(100) + 120)/100} >>> puts Time.now-t >>> end > 1.200484 > >>> begin > ?> t=Time.now >>> 1000000.times{rand < 0.80 ? 1 : 2} >>> puts Time.now-t >>> end > 1.249109 > >>> begin > ?> t=Time.now >>> 1000000.times{[1,2,2,2,2][rand(5)]} >>> puts Time.now-t >>> end > 1.498434 > >>> ...there''s many ways to skin a cat :-) >> >> But how fast can you do it? > > A fair bit faster if I don''t build the array in every loop ;-) > >>> x=[1,2,2,2,2] > => [1, 2, 2, 2, 2] >>> begin > ?> t=Time.now >>> 1000000.times{x[rand(5)]} >>> puts Time.now-t >>> end > 1.026202OK, I admit defeat. I am using ruby 1.8.7 which may be the reason for the different ratios you are seeing (assuming you are using 1.9.2). Interestingly the benefit of your technique is even greater on 1.8.7, taking only 0.67 secs on my machine. Colin -- You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org To unsubscribe from this group, send email to rubyonrails-talk+unsubscribe@googlegroups.com. For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en.
Michael Pavling
2011-Mar-12 22:16 UTC
Re: [RUBY] how do generate a random number w specific distribution ( which library ?)
On 12 March 2011 22:01, Colin Law <clanlaw-gM/Ye1E23mwN+BqQ9rBEUg@public.gmane.org> wrote:> OK, I admit defeat. the benefit of your technique is even greater on 1.8.7, > taking only 0.67 secs on my machine.Nah! Who cares if it takes half-a-second or a second to select a million random numbers.... any of the methods are perfect for selecting one number. Was a nice distraction from the recent run of posts... -- You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org To unsubscribe from this group, send email to rubyonrails-talk+unsubscribe@googlegroups.com. For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en.
Colin Law
2011-Mar-12 22:23 UTC
Re: [RUBY] how do generate a random number w specific distribution ( which library ?)
On 12 March 2011 22:16, Michael Pavling <pavling-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:> On 12 March 2011 22:01, Colin Law <clanlaw-gM/Ye1E23mwN+BqQ9rBEUg@public.gmane.org> wrote: >> OK, I admit defeat. the benefit of your technique is even greater on 1.8.7, >> taking only 0.67 secs on my machine. > > Nah! Who cares if it takes half-a-second or a second to select a > million random numbers.... any of the methods are perfect for > selecting one number.The OP might be doing some statistical simulation, so might need millions of values, but probably not. Colin> > Was a nice distraction from the recent run of posts... > > -- > You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. > To post to this group, send email to rubyonrails-talk-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org > To unsubscribe from this group, send email to rubyonrails-talk+unsubscribe@googlegroups.com. > For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en. > >-- You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org To unsubscribe from this group, send email to rubyonrails-talk+unsubscribe@googlegroups.com. For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en.
Conrad Taylor
2011-Mar-12 23:29 UTC
Re: [RUBY] how do generate a random number w specific distribution ( which library ?)
On Sat, Mar 12, 2011 at 1:07 PM, Colin Law <clanlaw-gM/Ye1E23mwN+BqQ9rBEUg@public.gmane.org> wrote:> On 12 March 2011 20:47, Michael Pavling <pavling-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote: > > On 12 March 2011 14:23, Colin Law <clanlaw-gM/Ye1E23mwN+BqQ9rBEUg@public.gmane.org> wrote: > >> On 12 March 2011 13:42, Rob Biedenharn <Rob-GBZH0y1GwQfnZcttdmLDtcI/UQi/AW5J@public.gmane.org> > wrote: > >>> def usually_one > >>> rand < 0.80 ? 1 : 2 > >>> end > >> > >> Yes, much better. I suppose it is the old programmer in me > >> instinctively avoiding floating point to save on processor time. A > >> bit silly when everything has hardware floating point. > > > > Although I prefer Rob''s suggestion as a better example of self > > documented code; this is another alternative... > > > > def usually_one > > [1,2,2,2,2][rand(5)] > > end > > > > Ha! Vindicated > > ruby-1.8.7-p302 > begin > ruby-1.8.7-p302 > t=Time.now > ruby-1.8.7-p302 ?> 1000000.times{(rand(100) + 120)/100} > ruby-1.8.7-p302 ?> puts Time.now-t > ruby-1.8.7-p302 ?> end > 0.905431 > > ruby-1.8.7-p302 > begin > ruby-1.8.7-p302 > t=Time.now > ruby-1.8.7-p302 ?> 1000000.times{rand < 0.80 ? 1 : 2} > ruby-1.8.7-p302 ?> puts Time.now-t > ruby-1.8.7-p302 ?> end > 1.712769 > > ruby-1.8.7-p302 > begin > ruby-1.8.7-p302 > t=Time.now > ruby-1.8.7-p302 ?> 1000000.times{ [1,2,2,2,2][rand(5)] } > ruby-1.8.7-p302 ?> puts Time.now-t > ruby-1.8.7-p302 ?> end > 1.150481 >Here''s my number from within and outside IRB from Mac OS 10.6.6: ruby-1.9.2-head :001 > begin ruby-1.9.2-head :002 > t=Time.now ruby-1.9.2-head :003?> 1000000.times{(rand(100) + 120)/100} ruby-1.9.2-head :004?> puts Time.now-t ruby-1.9.2-head :005?> end from-irb: 0.16657 from-ruby-script: 0.159452 ruby-1.9.2-head :006 > begin ruby-1.9.2-head :007 > t=Time.now ruby-1.9.2-head :008?> 1000000.times{rand < 0.80 ? 1 : 2} ruby-1.9.2-head :009?> puts Time.now-t ruby-1.9.2-head :010?> end from-irb: 0.280634 from-ruby-script: 0.150247 ruby-1.9.2-head :011 > begin ruby-1.9.2-head :012 > t=Time.now ruby-1.9.2-head :013?> 1000000.times{[1,2,2,2,2][rand(5)]} ruby-1.9.2-head :014?> puts Time.now-t ruby-1.9.2-head :015?> end from-irb: 0.521992 from-ruby-script: 0.35944 -Conrad> > > ...there''s many ways to skin a cat :-) > > But how fast can you do it? > > Colin > > -- > You received this message because you are subscribed to the Google Groups > "Ruby on Rails: Talk" group. > To post to this group, send email to rubyonrails-talk-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org > To unsubscribe from this group, send email to > rubyonrails-talk+unsubscribe-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org > For more options, visit this group at > http://groups.google.com/group/rubyonrails-talk?hl=en. > >-- You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org To unsubscribe from this group, send email to rubyonrails-talk+unsubscribe-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en.
Colin Law
2011-Mar-13 08:45 UTC
Re: [RUBY] how do generate a random number w specific distribution ( which library ?)
On 12 March 2011 23:29, Conrad Taylor <conradwt-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:> On Sat, Mar 12, 2011 at 1:07 PM, Colin Law <clanlaw-gM/Ye1E23mwN+BqQ9rBEUg@public.gmane.org> wrote: >> >> On 12 March 2011 20:47, Michael Pavling <pavling-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote: >> > On 12 March 2011 14:23, Colin Law <clanlaw-gM/Ye1E23mwN+BqQ9rBEUg@public.gmane.org> wrote: >> >> On 12 March 2011 13:42, Rob Biedenharn <Rob-GBZH0y1GwQfnZcttdmLDtcI/UQi/AW5J@public.gmane.org> >> >> wrote: >> >>> def usually_one >> >>> rand < 0.80 ? 1 : 2 >> >>> end >> >> >> >> Yes, much better. I suppose it is the old programmer in me >> >> instinctively avoiding floating point to save on processor time. A >> >> bit silly when everything has hardware floating point. >> > >> > Although I prefer Rob''s suggestion as a better example of self >> > documented code; this is another alternative... >> > >> > def usually_one >> > [1,2,2,2,2][rand(5)] >> > end >> > >> >> Ha! Vindicated >> >> ruby-1.8.7-p302 > begin >> ruby-1.8.7-p302 > t=Time.now >> ruby-1.8.7-p302 ?> 1000000.times{(rand(100) + 120)/100} >> ruby-1.8.7-p302 ?> puts Time.now-t >> ruby-1.8.7-p302 ?> end >> 0.905431 >> >> ruby-1.8.7-p302 > begin >> ruby-1.8.7-p302 > t=Time.now >> ruby-1.8.7-p302 ?> 1000000.times{rand < 0.80 ? 1 : 2} >> ruby-1.8.7-p302 ?> puts Time.now-t >> ruby-1.8.7-p302 ?> end >> 1.712769 >> >> ruby-1.8.7-p302 > begin >> ruby-1.8.7-p302 > t=Time.now >> ruby-1.8.7-p302 ?> 1000000.times{ [1,2,2,2,2][rand(5)] } >> ruby-1.8.7-p302 ?> puts Time.now-t >> ruby-1.8.7-p302 ?> end >> 1.150481 > > Here''s my number from within and outside IRB from Mac OS 10.6.6: > ruby-1.9.2-head :001 > begin > ruby-1.9.2-head :002 > t=Time.now > ruby-1.9.2-head :003?> 1000000.times{(rand(100) + 120)/100} > ruby-1.9.2-head :004?> puts Time.now-t > ruby-1.9.2-head :005?> end > from-irb: 0.16657 from-ruby-script: 0.159452I think I need a new laptop. Colin> ruby-1.9.2-head :006 > begin > ruby-1.9.2-head :007 > t=Time.now > ruby-1.9.2-head :008?> 1000000.times{rand < 0.80 ? 1 : 2} > ruby-1.9.2-head :009?> puts Time.now-t > ruby-1.9.2-head :010?> end > from-irb: 0.280634 from-ruby-script: 0.150247 > ruby-1.9.2-head :011 > begin > ruby-1.9.2-head :012 > t=Time.now > ruby-1.9.2-head :013?> 1000000.times{[1,2,2,2,2][rand(5)]} > ruby-1.9.2-head :014?> puts Time.now-t > ruby-1.9.2-head :015?> end > from-irb: 0.521992 from-ruby-script: 0.35944 > -Conrad > >> >> > ...there''s many ways to skin a cat :-) >> >> But how fast can you do it? >> >> Colin >> >> -- >> You received this message because you are subscribed to the Google Groups >> "Ruby on Rails: Talk" group. >> To post to this group, send email to rubyonrails-talk-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org >> To unsubscribe from this group, send email to >> rubyonrails-talk+unsubscribe-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org >> For more options, visit this group at >> http://groups.google.com/group/rubyonrails-talk?hl=en. >> > > -- > You received this message because you are subscribed to the Google Groups > "Ruby on Rails: Talk" group. > To post to this group, send email to rubyonrails-talk-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org > To unsubscribe from this group, send email to > rubyonrails-talk+unsubscribe-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org > For more options, visit this group at > http://groups.google.com/group/rubyonrails-talk?hl=en. >-- You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org To unsubscribe from this group, send email to rubyonrails-talk+unsubscribe@googlegroups.com. For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en.
Martin Streicher
2011-Mar-15 13:37 UTC
Re: [RUBY] how do generate a random number w specific distribution ( which library ?)
I use this often:
class Uuid
def self.uuid
return rand( 18446744073709551615 ).to_s( 36 ).rjust( 13,
''0'' )
end
end
See http://blog.locomotivellc.com/post/3277434038/unique-ids
On Mar 13, 4:45 am, Colin Law
<clan...-gM/Ye1E23mwN+BqQ9rBEUg@public.gmane.org>
wrote:> On 12 March 2011 23:29, Conrad Taylor
<conra...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
>
>
>
>
>
> > On Sat, Mar 12, 2011 at 1:07 PM, Colin Law
<clan...-gM/Ye1E23mwN+BqQ9rBEUg@public.gmane.org> wrote:
>
> >> On 12 March 2011 20:47, Michael Pavling
<pavl...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
> >> > On 12 March 2011 14:23, Colin Law
<clan...-gM/Ye1E23mwN+BqQ9rBEUg@public.gmane.org> wrote:
> >> >> On 12 March 2011 13:42, Rob Biedenharn
<R...-GBZH0y1GwQfnZcttdmLDtcI/UQi/AW5J@public.gmane.org>
> >> >> wrote:
> >> >>> def usually_one
> >> >>> rand < 0.80 ? 1 : 2
> >> >>> end
>
> >> >> Yes, much better. I suppose it is the old programmer in
me
> >> >> instinctively avoiding floating point to save on
processor time. A
> >> >> bit silly when everything has hardware floating point.
>
> >> > Although I prefer Rob''s suggestion as a better
example of self
> >> > documented code; this is another alternative...
>
> >> > def usually_one
> >> > [1,2,2,2,2][rand(5)]
> >> > end
>
> >> Ha! Vindicated
>
> >> ruby-1.8.7-p302 > begin
> >> ruby-1.8.7-p302 > t=Time.now
> >> ruby-1.8.7-p302 ?> 1000000.times{(rand(100) + 120)/100}
> >> ruby-1.8.7-p302 ?> puts Time.now-t
> >> ruby-1.8.7-p302 ?> end
> >> 0.905431
>
> >> ruby-1.8.7-p302 > begin
> >> ruby-1.8.7-p302 > t=Time.now
> >> ruby-1.8.7-p302 ?> 1000000.times{rand < 0.80 ? 1 : 2}
> >> ruby-1.8.7-p302 ?> puts Time.now-t
> >> ruby-1.8.7-p302 ?> end
> >> 1.712769
>
> >> ruby-1.8.7-p302 > begin
> >> ruby-1.8.7-p302 > t=Time.now
> >> ruby-1.8.7-p302 ?> 1000000.times{ [1,2,2,2,2][rand(5)] }
> >> ruby-1.8.7-p302 ?> puts Time.now-t
> >> ruby-1.8.7-p302 ?> end
> >> 1.150481
>
> > Here''s my number from within and outside IRB from Mac OS
10.6.6:
> > ruby-1.9.2-head :001 > begin
> > ruby-1.9.2-head :002 > t=Time.now
> > ruby-1.9.2-head :003?> 1000000.times{(rand(100) + 120)/100}
> > ruby-1.9.2-head :004?> puts Time.now-t
> > ruby-1.9.2-head :005?> end
> > from-irb: 0.16657 from-ruby-script: 0.159452
>
> I think I need a new laptop.
>
> Colin
>
>
>
> > ruby-1.9.2-head :006 > begin
> > ruby-1.9.2-head :007 > t=Time.now
> > ruby-1.9.2-head :008?> 1000000.times{rand < 0.80 ? 1 : 2}
> > ruby-1.9.2-head :009?> puts Time.now-t
> > ruby-1.9.2-head :010?> end
> > from-irb: 0.280634 from-ruby-script: 0.150247
> > ruby-1.9.2-head :011 > begin
> > ruby-1.9.2-head :012 > t=Time.now
> > ruby-1.9.2-head :013?> 1000000.times{[1,2,2,2,2][rand(5)]}
> > ruby-1.9.2-head :014?> puts Time.now-t
> > ruby-1.9.2-head :015?> end
> > from-irb: 0.521992 from-ruby-script: 0.35944
> > -Conrad
>
> >> > ...there''s many ways to skin a cat :-)
>
> >> But how fast can you do it?
>
> >> Colin
>
> >> --
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Michael Pavling
2011-Mar-15 13:46 UTC
Re: Re: [RUBY] how do generate a random number w specific distribution ( which library ?)
On 15 March 2011 13:37, Martin Streicher <martin.streicher-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:> I use this often: > > class Uuid > def self.uuid > return rand( 18446744073709551615 ).to_s( 36 ).rjust( 13, ''0'' ) > end > endNice, simple process (assuming it works... I''ve not tried it), but I don''t think it has much to do with the topic of this thread, and it''s not likely to create a *real* UUID (RFC4122) is it? This old thread discusses it a bit: http://www.ruby-forum.com/topic/164078 -- You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org To unsubscribe from this group, send email to rubyonrails-talk+unsubscribe@googlegroups.com. For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en.
Ar Chron
2011-Mar-15 17:14 UTC
Re: [RUBY] how do generate a random number w specific distribution ( which library ?)
Colin Law wrote in post #987114:> > But how fast can you do it? >Ooh, that''s an evil tweak... (a minor diversion which is much more fun than what I was doing) Lenovo T61p, Core2Duo, T9300, 2.5GHz, ruby 1.9.2-p0 = 0.253025 And for curiosity, my Ubuntu 10.10 VM on top of the same hardware: = 0.323791 -- Posted via http://www.ruby-forum.com/. -- You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org To unsubscribe from this group, send email to rubyonrails-talk+unsubscribe-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en.
Martin Streicher
2011-Mar-15 19:52 UTC
Re: how do generate a random number w specific distribution ( which library ?)
I don''t think it makes a true UUID, but I''ve run it into the billions and never got a repeat. So, effectively, it acts like UUID. -- You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org To unsubscribe from this group, send email to rubyonrails-talk+unsubscribe-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en.