[Scilab-users] Ways to speed up simple things in Scilab ?

[Stéphane Mottelet]

Hello,

Ok, I will try dynamic link since I want the project to stay into the 
Scilab world, but another alternative is Julia (http://julialang.org/). 
I have made some tests this night and got a speedup of 25, the 
explanation is JIT compilation. Maybe will we have JIT compilation in 
Scilab 6 ?

Best regards,

S.

Le 24/04/2015 09:30, aweeks at hidglobal.com a écrit :
> Hello Stephane,
>
> We have a Scilab program which performs a  numerical integration on 
> data points in 3-dimensions - it has two nested loops.  When the 
> number of data points was large this was slow so we implemented the 
> calculation function in C and got a speed improvement of about 24 times !
>
> We also found three other improvements:
>
>         using pointer arithmetic was faster than 'for' loops,
>         'pow(x, 2)' was faster than x*x,
>         handling the data as 3 (N x 1) vectors was faster than using 1 
> (N x 3) matrix.
>
> each of these giving something like a 3-4% improvement - small 
> compared to x24 but still worth having.
>
> If you don't mind tackling the dynamic linking it's probably worth the 
> effort if you'll use this program a few times - good luck.
>
> Adrian.
>
> *Adrian Weeks *
> Development Engineer, Hardware Engineering EMEA
> Office: +44 (0)2920 528500 | Desk: +44 (0)2920 528523 | Fax: +44 
> (0)2920 520178_
> __aweeks at hidglobal.com_ <mailto:aweeks at hidglobal.com>
> HID Global Logo <http://www.hidglobal.com/>
> Unit 3, Cae Gwyrdd,
> Green meadow Springs,
> Cardiff, UK,
> CF15 7AB._
> __www.hidglobal.com_ <http://www.hidglobal.com/>
>
>
>
>
>
> From: 	Stéphane Mottelet <stephane.mottelet at utc.fr>
> To: 	"International users mailing list for Scilab." 
> <users at lists.scilab.org>
> Date: 	23/04/2015 22:52
> Subject: 	[Scilab-users] Ways to speed up simple things in Scilab ?
> Sent by: 	"users" <users-bounces at lists.scilab.org>
>
>
> ------------------------------------------------------------------------
>
>
>
> Hello,
>
> I am currently working on a project where Scilab code is automatically
> generated, and after many code optimization, the remaining bottleneck is
> the time that Scilab spends to execute simple code like this (full
> script (where the vector has 839 lines) with timings is attached) :
>
> M1_v=[v(17)
> v(104)
> v(149)
> -(v(18)+v(63)+v(103))
> -(v(18)+v(63)+v(103))
> v(17)
> ...
> v(104)
> v(149)
> ]
>
> This kind of large vectors are the used to build a sparse matrix each
> time the vector v changes, but with a constant sparsity pattern.
> Actually, the time spent by Scilab in the statement
>
> M1=sparse(M1_ij,M1_v,[n1,n2])
>
> is negligible compared to the time spent to build f M1_v...
>
> I have also noticed that if you need to define such a matrix with more
> that one column, the time elapsed is not linear with respect to the
> number of columns: typically 4 times slower for 2 columns. In fact the
> statement
>
> v=[1 1
> ...
> 1000 1000]
>
> is even two times slower than
>
> v1=[1
> ...
> 1000];
> v2=[1
> ....
> 1000];
> v=[v1 v2];
>
> So my question to users who have the experience of dynamic link of user
> code : do you think that using dynamic link of compiled generated C code
> could improve the timings ?
>
> In advance, thanks for your help !
>
> S.
>
>
> [attachment "test.sce" deleted by Adrian Weeks/CWL/EU/ITG] 
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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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