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<p><font face="Arial">Dear co-scilabers,</font></p>
<p><font face="Arial">The <a href="http://bugzilla.scilab.org/8297">bug
8297</a> reporting the outstanding slowness of the cat()
function was reported in 2010<br>
but lasts since cat() was introduced. As measured and commented
in the report, this<br>
slowness actually makes cat() almost unusable, except for small
sized arrays to be concatenated.<br>
</font></p>
<p><font face="Arial">For instance, after M = rand(500,500);
cat(3,M,M) takes more than 11 days (yes)<br>
with Scilab 5.5.2, and roughly 4 hours with Scilab 6.0.0.</font></p>
<p><font face="Arial">So, everyone could imagine how much Scilab
currently takes just to build a standard<br>
1000x1000 RGB image by stacking its 3 1000x1000 R,G,B layers
using cat(3,R,G,B).<br>
The current algorithm is exponential with respect to the array
size...</font></p>
<p><font face="Arial">Before using GPU routines to process images, a
much simpler thing can be done<br>
to enable cat() for true life usages : rewritting it.<br>
This is what is done here:
<a class="moz-txt-link-freetext" href="https://codereview.scilab.org/#/c/19278/">https://codereview.scilab.org/#/c/19278/</a></font></p>
<p><font face="Arial">Some rewievers are needed to make cat() truly
available in Scilab 6.0.1.<br>
So, do not hesitate to contribute online.<br>
</font></p>
<p><font face="Arial">Thank you.<br>
Samuel<br>
<br>
</font></p>
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