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

[Antoine Monmayrant]

Le 04/24/2015 03:19 PM, Brian Bouterse a écrit :
> I don't know much about scilab optimizations, but trying to 
> hand-optimize auto-generated code almost certainly will result in 
> correctness problems. It's likely better to make your improvements in 
> the software that is generating the scilab code. I think the main 
> feature there is to have it generate a vectorized implementation 
> instead of a procedural one (as you have now).

I agree with you: scilab is fast with linear algebra and slow for the 
rest and so far you have not generated your scilab code with scilab 
strength and weakness in mind.
So if you stick with Scilab, you should go for a matrix form (maybe a 
sparse matrix) or follow Samuel's version.

Cheers,

Antoine

>
> -Brian
>
> On Fri, Apr 24, 2015 at 8:34 AM, Stéphane Mottelet 
> <stephane.mottelet at utc.fr <mailto:stephane.mottelet at utc.fr>> wrote:
>
>     Hello,
>
>     this is not trivial indexing, in fact some terms are linear
>     combination of v's components
>
>     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)
>     ]
>
>     How do you take this into account in your proposed method ? These
>     combinations are sums of influxes in a metabolic network, and the
>     code is automatically generated.
>
>
>     S.
>
>
>
>     Le 24/04/2015 13:48, Samuel Gougeon a écrit :
>>     Le 24/04/2015 13:36, Samuel Gougeon a écrit :
>>>     Hello Stephane,
>>>
>>>     You can speed up by a factor larger than 100 just by calling v
>>>     once (or 3 times) instead of ~1000, as shown by this test:
>>
>>     Actually, to be more accurate, the right comparative test is the
>>     following:
>>
>>     function  test2()
>>          v  =  rand(172,1);
>>          p  =  grand(1,839,"unf",1,173)
>>          // Part 1: 1 call to v()
>>          tic()
>>          for  i=1:1000
>>              m1_v  =  v(p)
>>          end
>>          disp(toc())
>>          
>>          // Part 2 : 839 calls to v()
>>          deff("test3()",  "for i=1:1000, M1_v = ["+strcat("v("+string(p)+")")+"], end")
>>          tic()
>>          test3()
>>          disp(toc())
>>     endfunction
>>
>>     In this version, the compilation time used by execstr() is no
>>     longer taken into account.
>>
>>     The results are still explicit:
>>     -->test2()
>>
>>         0.016
>>
>>         0.78
>>
>>     So, a speed-up by ~x 50
>>
>>     Samuel
>>
>>
>>
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>
>
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>
> -- 
> Brian Bouterse
>
>
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