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<div class="moz-cite-prefix">Hi Samuel, et al.<br>
<br>
>Doesn't it fit more to what could be expected?<br>
<br>
Yes. Absolutely. Sorry that I don't know how to help verify the
code.<br>
<br>
/Claus<br>
<br>
On 10-08-2017 20:03, Samuel Gougeon wrote:<br>
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<div class="moz-cite-prefix">Le 10/08/2017 à 19:55, Samuel Gougeon
a écrit :<br>
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cite="mid:504a26d7-5ee5-217f-2e40-302d63a05883@free.fr"
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<p><font face="Arial">Dear co-scilabers,</font></p>
<p><font face="Arial">The <a moz-do-not-send="true"
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 moz-do-not-send="true"
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>
</blockquote>
<br>
To complete: This new implementation spends 0.25 s (instead of 4
hours) to execute<br>
<pre class="bz_comment_text" id="comment_text_5">M = rand(500,500);
cat(3,M,M);
</pre>
and 0.42 s to process<br>
<br>
M = rand(1000,1000);<br>
cat(3,M,M,M);<br>
<br>
Doesn't it fit more to what could be expected?<br>
SG<br>
<br>
<br>
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<p><br>
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