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

[Antoine Monmayrant]

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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