Re: are cell arrays slow?

[kensmith]

On Monday 27 August 2007 02:13, Bertrand Roessli wrote:
> Hello,
>
> I have tried the following test code and I have the
> feeling that working with cell arrays is slow. Do I make a mistake
> somewhere?

No mistake is obvious to me.
>
>
> nr=1000;
>
> for i=1:nr
>         mom.mx=i;
>         mom.my=2*i;
>         a{i}=mom;
> endfor
>
>
> tic;
> [[a{1:nr}].mx].+[[a{1:nr}].my];
> toc

I am almost surprised that this takes much time at all.  If the 
calculation is done as shown, three arrays need to be allocated.  This 
may take longer than doing the "+".  I would have expected there to be 
some optimizing that would have reduced the amount of allocating and 
de-allocating.  Since this statement produces no result, a very good 
optimizer would have reduced it to nothing.


> tic;
> for i=1:nr
>         a{i}.mx.+a{i}.my;
> endfor
> toc

Here we are looping but not allocating.  Perhaps the loop method has 
been very optimized.

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