slow access to objects within 'cell' variables

[Jaroslav Hajek]

On Thu, Jan 8, 2009 at 4:50 PM, Łukasz Sowiński <lukasz.sowinski at post.pl> wrote:
> Bug report for Octave 3.0.3 configured for i686-pc-linux-gnu
>
> Description:
> -----------
>
>  * Access to objects within cell type depends on their size and can be
> really slow.
>    F.i. if
>       a{1} = zeros(1, 10);
>       b{1} = zeros(1, 10000000);
>    then
>       a{1}(1) = 1;
>    is much faster than
>       b{1}(1) = 1;
>    .
>
> Repeat-By:
> ---------
>
>  * Please execute the following code:
>
>      n_write = 1000;
>      for n_alloc = n_write*[1 10 100 1000]
>         y{1} = zeros(1, n_alloc);
>         timer = -cputime;
>         for i=1:n_write
>            y{1}(:, i) = 1;
>         endfor
>         disp(timer + cputime);
>      endfor
>
>
>

I've uploaded the following patch, which seems to fix this problem:
http://hg.savannah.gnu.org/hgweb/octave/rev/7b25349b32e6

Also, doing
a{1} = zeros(1,10);
a{1:2}(1) = 1
will now give an error as in Matlab.

thanks for this report,

-- 
RNDr. Jaroslav Hajek
computing expert
Aeronautical Research and Test Institute (VZLU)
Prague, Czech Republic
url: www.highegg.matfyz.cz