[Scilab-Dev] Scilab index type should be generalized

[Samuel Gougeon]

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

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