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

[Stéphane Mottelet]

Hello Antoine 

I think your idea is excellent in my context, I Will try it and keep you informed of the actual improvement,

S.

> Le 24 avr. 2015 à 13:31, Antoine Monmayrant <antoine.monmayrant at laas.fr> a écrit :
> 
> Hi again,
> 
> Another way you might improve your code: can you write it as a matrix-vector product?
> Like
> 
> M1_v=A*v; 
> Where A is a matrix of size (839,172) that corresponds to your weird combination of v(i) to build M1_v.
> It seems to me that you should be able to write it that way, which would save a lot of time as matrix product are fast in Scilab.
> 
> Antoine
> 
> 
> Le 04/23/2015 11:51 PM, Stéphane Mottelet a écrit :
>> 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. 
>> 
>> 
>> 
>> 
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