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[Octave-bug-tracker] [bug #45447] image package: strel decomposition doe
From: |
H. G. |
Subject: |
[Octave-bug-tracker] [bug #45447] image package: strel decomposition does not speed things up |
Date: |
Tue, 30 Jun 2015 19:52:38 +0000 |
User-agent: |
Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:38.0) Gecko/20100101 Firefox/38.0 |
URL:
<http://savannah.gnu.org/bugs/?45447>
Summary: image package: strel decomposition does not speed
things up
Project: GNU Octave
Submitted by: hardy
Submitted on: Di 30 Jun 2015 19:52:36 GMT
Category: Octave Forge Package
Severity: 3 - Normal
Priority: 5 - Normal
Item Group: Performance
Status: None
Assigned to: None
Originator Name:
Originator Email:
Open/Closed: Open
Discussion Lock: Any
Release: 4.0.0
Operating System: Any
_______________________________________________________
Details:
Here is a little script to show the behavior. It is mostly taken from the
example code for "strel decomposition" that you can find in the help text of
strel.m :
clear
pkg load image
im = randp (5, 2000) > 15;
n=20;
se = strel ("square", n);
% test the speed with imdilate:
t = cputime ();
imdilate (im, se);
cputime () - t
se = strel (ones (n));
t = cputime ();
imdilate (im, se);
cputime () - t
% make sure that the se can be decomposed at all:
se
seq = getsequence(se);
number_of_decomps = max(size((seq))) % returns 2*1 = YES
The help text of strel.m states that there should be a significant difference
in executioin time (0.77 s versus 2.9 s is written there). But if I do this
with Octave-4.0.0 and image-2.4.0. then I see hardyl any differenc in
execution time (mostly around 1.13s versus 1.12s on my elderly laptop).
The last lines of the script tell me, that this se can be decomposed,
getsequence returns 2 parts. But I am not sure that imdilate uses this
decomposition at all.
Note: I had to use "size(se)" in the script, because "length(se)" did not
work, it returned the value 1 instead of 2. Is this a bug on its own, or
intenional?
_______________________________________________________
Reply to this item at:
<http://savannah.gnu.org/bugs/?45447>
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- [Octave-bug-tracker] [bug #45447] image package: strel decomposition does not speed things up,
H. G. <=