I have a series of objects in an array. Each object corresponds to an
application and has several attributes. For instance I can call:
@application.name
@application.icon
@application.ranking
"ranking" is always an integer. So if I have an array of these objects,
say, @allApplications how do I sort using each application's ranking
(@application.ranking)?
--
Posted via http://www.ruby-forum.com/.
applications.sort_by{|object| object.ranking}
On 08/03/07, Jason Burgett <jasbur@gmail.com> wrote:
I have a series of objects in an array. Each object corresponds to an
application and has several attributes. For instance I can call:@application.name
@application.icon
@application.ranking"ranking" is always an integer. So if I have an array of these objects,
say, @allApplications how do I sort using each application's ranking
(@application.ranking)?
Farrel Lifson wrote:
I have a series of objects in an array. Each object corresponds to an
application and has several attributes. For instance I can call:@application.name
@application.icon
@application.ranking"ranking" is always an integer. So if I have an array of these objects,
say, @allApplications how do I sort using each application's ranking
(@application.ranking)?applications.sort_by{|object| object.ranking}
Another way would be to add a <=> method
class Application
def <=> other
self.ranking <=> other.ranking
end
end
-Justin
On 08/03/07, Jason Burgett <jasbur@gmail.com> wrote:
Using only <=> does have some speed consequences:
require 'benchmark'
srand
class Application
attr_reader :ranking
def initialize
@ranking = rand
end
def <=>(other)
@ranking <=> other.ranking
end
end
applications = Array.new(1000000){Application.new}
Benchmark.bm do |bmark|
bmark.report("Sort") { applications.sort }
bmark.report("Sort By") {applications.sort_by {|o| o.ranking}}
end
C:\Documents and Settings\flifson\Desktop>ruby sort_test.rb
user system total real
Sort 20.782000 0.031000 20.813000 ( 20.844000)
Sort By 6.687000 0.000000 6.687000 ( 6.687000)
Farrel
On 08/03/07, Justin Collins <collinsj@seattleu.edu> wrote:
Farrel Lifson wrote:
> On 08/03/07, Jason Burgett <jasbur@gmail.com> wrote:
>> I have a series of objects in an array. Each object corresponds to an
>> application and has several attributes. For instance I can call:
>>
>> @application.name
>> @application.icon
>> @application.ranking
>>
>> "ranking" is always an integer. So if I have an array of these objects,
>> say, @allApplications how do I sort using each application's ranking
>> (@application.ranking)?
>>
>
> applications.sort_by{|object| object.ranking}
>Another way would be to add a <=> method
class Application
def <=> other
self.ranking <=> other.ranking
end
end-Justin
I don't understand, can someone please explain this loss of speed?
On 8 Mrz., 08:09, "Farrel Lifson" <farrel.lif...@gmail.com> wrote:
On 08/03/07, Justin Collins <colli...@seattleu.edu> wrote:
> Farrel Lifson wrote:
> > On 08/03/07, Jason Burgett <jas...@gmail.com> wrote:
> >> I have a series of objects in an array. Each object corresponds to an
> >> application and has several attributes. For instance I can call:> >> @application.name
> >> @application.icon
> >> @application.ranking> >> "ranking" is always an integer. So if I have an array of these objects,
> >> say, @allApplications how do I sort using each application's ranking
> >> (@application.ranking)?> > applications.sort_by{|object| object.ranking}
> Another way would be to add a <=> method
> class Application
> def <=> other
> self.ranking <=> other.ranking
> end
> end> -Justin
Using only <=> does have some speed consequences:
require 'benchmark'
srandclass Application
attr_reader :ranking
def initialize
@ranking = rand
end
def <=>(other)
@ranking <=> other.ranking
end
endapplications = Array.new(1000000){Application.new}
Benchmark.bm do |bmark|
bmark.report("Sort") { applications.sort }
bmark.report("Sort By") {applications.sort_by {|o| o.ranking}}
endC:\Documents and Settings\flifson\Desktop>ruby sort_test.rb
user system total real
Sort 20.782000 0.031000 20.813000 ( 20.844000)
Sort By 6.687000 0.000000 6.687000 ( 6.687000)Farrel- Zitierten Text ausblenden -
- Zitierten Text anzeigen -
rretzbach wrote:
On 8 Mrz., 08:09, "Farrel Lifson" <farrel.lif...@gmail.com> wrote:
On 08/03/07, Justin Collins <colli...@seattleu.edu> wrote:
Farrel Lifson wrote:
On 08/03/07, Jason Burgett <jas...@gmail.com> wrote:
I have a series of objects in an array. Each object corresponds to an
application and has several attributes. For instance I can call:
@application.name
@application.icon
@application.ranking
"ranking" is always an integer. So if I have an array of these objects,
say, @allApplications how do I sort using each application's ranking
(@application.ranking)?
applications.sort_by{|object| object.ranking}
Another way would be to add a <=> method
class Application
def <=> other
self.ranking <=> other.ranking
end
end
-Justin
Using only <=> does have some speed consequences:
require 'benchmark'
srandclass Application
attr_reader :ranking
def initialize
@ranking = rand
end
def <=>(other)
@ranking <=> other.ranking
end endapplications = Array.new(1000000){Application.new}
Benchmark.bm do |bmark|
bmark.report("Sort") { applications.sort }
bmark.report("Sort By") {applications.sort_by {|o| o.ranking}}
endC:\Documents and Settings\flifson\Desktop>ruby sort_test.rb
user system total real
Sort 20.782000 0.031000 20.813000 ( 20.844000)
Sort By 6.687000 0.000000 6.687000 ( 6.687000)Farrel- Zitierten Text ausblenden -
- Zitierten Text anzeigen -
I don't understand, can someone please explain this loss of speed?
I'm guessing it has to do with Enumerable#sort_by doing the key caching thing?
-Justin
Sorting compares pairs of objects many more times than the number of
objects actually being sorted. The <=> method extracts the ranking
from the objects each time a pair is compared. The sort_by method only
extracts the ranking from each object once then compares these. The
time difference represents the overhead of the <=> method call and the
time required to retrieve instance variables for each of the pair.
On Mar 8, 9:19 pm, "rretzbach" <rretzb...@googlemail.com> wrote:
On 8 Mrz., 08:09, "Farrel Lifson" <farrel.lif...@gmail.com> wrote:
> On 08/03/07, Justin Collins <colli...@seattleu.edu> wrote:
> > Farrel Lifson wrote:
> > > On 08/03/07, Jason Burgett <jas...@gmail.com> wrote:
> > >> I have a series of objects in an array. Each object corresponds to an
> > >> application and has several attributes. For instance I can call:> > >> @application.name
> > >> @application.icon
> > >> @application.ranking> > >> "ranking" is always an integer. So if I have an array of these objects,
> > >> say, @allApplications how do I sort using each application's ranking
> > >> (@application.ranking)?> > > applications.sort_by{|object| object.ranking}
> > Another way would be to add a <=> method
> > class Application
> > def <=> other
> > self.ranking <=> other.ranking
> > end
> > end> > -Justin
> Using only <=> does have some speed consequences:
> require 'benchmark'
> srand> class Application
> attr_reader :ranking
> def initialize
> @ranking = rand
> end
> def <=>(other)
> @ranking <=> other.ranking
> end
> end> applications = Array.new(1000000){Application.new}
> Benchmark.bm do |bmark|
> bmark.report("Sort") { applications.sort }
> bmark.report("Sort By") {applications.sort_by {|o| o.ranking}}
> end> C:\Documents and Settings\flifson\Desktop>ruby sort_test.rb
> user system total real
> Sort 20.782000 0.031000 20.813000 ( 20.844000)
> Sort By 6.687000 0.000000 6.687000 ( 6.687000)> Farrel- Zitierten Text ausblenden -
> - Zitierten Text anzeigen -
I don't understand, can someone please explain this loss of speed?