[Scilab-Dev] Scilab index type should be generalized

[Stéphane Mottelet]

Le 23/03/2016 11:59, Samuel Gougeon a écrit :
> Hello Stéphane,
>
> Le 23/03/2016 10:05, Stéphane Mottelet a écrit :
>> .../...
>> This means that Scilab handles 1:10 as any other vector of 
>> scrambled/duplicate indices without seeing that all the components 
>> are contiguous in memory. In fact, this behavior is a major 
>> bottleneck, as illustrated in the following (Scilab 5.5.2 timings on 
>> a Xeon E5-2660 v2 (2.20 GHz) )
>>
>> --> n=200000;a=rand(n,1);
>>
>> --> timer();for i=1:1000;sum(a(10:100000));end;disp(timer())
>>
>>     1.51426
>>
>> --> timer();for i=1:1000;sum(a($-n+10:$-n+100000));end;disp(timer())
>>
>>     0.588478
>>
>> almost three times faster... 
>
> On my PC, i get with Scilab 6.0b1 / win7_x64, in a ~reproducible way 
> (for the ratio) :
> -->  timer();for i=1:1000;sum(a(10:100000));end;disp(timer())
>    2.1996141
>
> --> timer();for i=1:1000;sum(a($-n+10:$-n+100000));end;disp(timer())
>    1.5756101
>
> Scilab 5.5.2 is slightly faster and the ratio is a bit more balanced:
> --> timer();for i=1:1000;sum(a(10:100000));end;disp(timer())
>     1.716011
>
> -->timer();for i=1:1000;sum(a($-n+10:$-n+100000));end;disp(timer())
>     1.4196091
>
>
> Samuel
on my MacPro mid 2010 (2,8 GHz Quad-Core Intel Xeon) , with Scilab 5.5.2:

-->timer();for i=1:1000;sum(a(10:100000));end;disp(timer())

     1.176976

--> timer();for i=1:1000;sum(a($-n+10:$-n+100000));end;disp(timer())

     0.565811

and with Scilab 6.0b1:

--> timer();for i=1:1000;sum(a(10:100000));end;disp(timer())

    1.22783

--> timer();for i=1:1000;sum(a($-n+10:$-n+100000));end;disp(timer())

    0.728778

The different ratios for different platforms are somehow understandable 
(different os, memory management, ...) but anyway disturbing !

S.

>
>
>
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-- 
Département de Génie Informatique
EA 4297 Transformations Intégrées de la Matière Renouvelable
Université de Technologie de Compiègne -  CS 60319
60203 Compiègne cedex

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