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List:       kde-usability
Subject:    Re: Konqueror Thumbnail Generation
From:       "Jamethiel Knorth" <jamethknorth () hotmail ! com>
Date:       2004-03-26 7:34:15
Message-ID: BAY7-F121U393IhJrvJ0000d1fc () hotmail ! com
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>From: Gérard Delafond <gerard@delafond.org>
>Date: Thu, 25 Mar 2004 23:37:12 +0100
>
>If Benoit adds a checking of the file size to decide reloading icons, it is
>ony a workaround, because some different files cans have the same size.
>

This is why I have been recommending using some hashing algorithm. I know 
that the extremely fast hashes are imperfect, but they will overlap FAR less 
than the filesizes will. I know that I run into filesize overlaps fairly 
regularly.

I don't know how well it would work in practice, but I just tested out on my 
system how fast CRC hashes come. It's a really simple method that just shows 
a little, but it seems fast to me. I just ran 'time check *' to generate CRC 
hashes on a variety of directories. It seems largely bound by filesize. 
Also, I did have other programs running, so there's tons of variance from 
that. I did a few huge directories recursively and then many small ones.

I don't like things that slow down the system, but I wonder how much it 
would actually slow things down.

Oh, and for the short version of the results, anything under 100 files 
finished in under 1 second, and it took 27 minutes for 12 gig directory of 
5800 files.

-------------

5875 files (not images)
12 gigabytes
real    27m42.758s
user    1m23.810s
sys     1m16.180s

4408 images
648 megabytes
real    1m12.477s
user    0m26.380s
sys     0m18.280s

68 images
2.9 megabytes
real    0m0.672s
user    0m0.040s
sys     0m0.060s

9 images
316 kilobytes
real    0m0.211s
user    0m0.020s
sys     0m0.010s

68 images
4.0 megabytes
real    0m0.613s
user    0m0.070s
sys     0m0.020s

68 images
5.2 megabytes
real    0m0.638s
user    0m0.050s
sys     0m0.070s

68 images
6.6 megabytes
real    0m0.765s
user    0m0.090s
sys     0m0.020s

31 images
452 kilobytes
real    0m0.103s
user    0m0.000s
sys     0m0.020s

6 images
44 kilobytes
real    0m0.135s
user    0m0.000s
sys     0m0.010s

16 images
568 kilobytes
real    0m0.275s
user    0m0.000s
sys     0m0.010s

By the way, none of these would have been in the cache, I made certain not 
to check any files twice. Also, my system was under decent load during the 
largest check.

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