Le 10/08/2017 à 19:55, Samuel Gougeon a écrit :
Dear co-scilabers,
The bug 8297 <http://bugzilla.scilab.org/8297> reporting the
outstanding slowness of the cat() function was reported in 2010
but lasts since cat() was introduced. As measured and commented in the
report, this
slowness actually makes cat() almost unusable, except for small sized
arrays to be concatenated.
For instance, after M = rand(500,500); cat(3,M,M) takes more than 11
days (yes)
with Scilab 5.5.2, and roughly 4 hours with Scilab 6.0.0.
So, everyone could imagine how much Scilab currently takes just to
build a standard
1000x1000 RGB image by stacking its 3 1000x1000 R,G,B layers using
cat(3,R,G,B).
The current algorithm is exponential with respect to the array size...
Before using GPU routines to process images, a much simpler thing can
be done
to enable cat() for true life usages : rewritting it.
This is what is done here: https://codereview.scilab.org/#/c/19278/
Some rewievers are needed to make cat() truly available in Scilab 6.0.1.
So, do not hesitate to contribute online.
To complete: This new implementation spends 0.25 s (instead of 4 hours)
to execute
M = rand(500,500);
cat(3,M,M);
and 0.42 s to process
M = rand(1000,1000);
cat(3,M,M,M);
Doesn't it fit more to what could be expected?
SG
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