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List: kde-imaging
Subject: Re: [Kde-imaging] Lossless image compression
From: Christoph Feck <christoph () maxiom ! de>
Date: 2012-02-08 15:42:55
Message-ID: 201202081642.55959.christoph () maxiom ! de
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On Tuesday 07 February 2012 15:43:19 Dmitry Kazakov wrote:
> Probably, I'm a bit outdated.
>
> I've just run the test on my new machine.
> The results are the following:
>
> Compression LZF w/o linearization: 247 memcpy's. Ratio: 0.938
> Compression LZF with linearization: 213 memcpy's. Ratio: 0.769
>
> Decompression LZF w/o linearization: 78 memcpy's.
> Decompression LZF with linearization: 112 memcpy's.
>
I am interested what exactly you are measuring. Either your memcpy is
blazingly fast, or mine is very slow.
I get the following CPU timings (i.e. only "user" part of "time"
output). I tried several times, and listed is the smallest value I
got. Machine is 1.2 GHz ULV Centrino, 32 bit, only one core used. Test
files from http://www.imagecompression.info/test_images/
First test: 7216x5412 "big_building.ppm", RGB 8-bit photo (112 MB)
memcpy: 0.126 s
bytecopy: 0.218 s
compression:
IZ p3: 2.947 s, ratio 0.494
IZ p2: 1.625 s, ratio 0.509
IZ p1: 1.488 s, ratio 0.546
LZF: 1.826 s, ratio 0.989
decompression:
IZ p3: 3.216 s
IZ p2: 1.779 s
IZ p1: 1.670 s
LZF: 0.544 s
Second test: 3072x2048 "artificial.ppm", RGB 8 bit raytraced (18 MB)
memcpy: 0.017 s
bytecopy: 0.035 s
compression:
IZ p3: 0.452 s, ratio 0.119
IZ p2: 0.235 s, ratio 0.139
IZ p1: 0.215 s, ratio 0.122
LZF: 0.114 s, ratio 0.189
decompression:
IZ p3: 0.491 s
IZ p2: 0.264 s
IZ p1: 0.217 s
LZF: 0.073 s
"memcpy" is what gnu libc 2.14.1 + gcc 4.6.2 combo provides in -O2
mode.
"bytecopy" is:
while (p != pend) {
*dest++ = *p++;
}
where dest and p are byte pointers.
"IZ p3" is IZ with (default) 3-pixel predictor. "IZ p2" and "IZ p1"
are IZ with 2-pixel and 1-pixel predictors, which trade some
compression rate for speed (preferred for swap compression).
"LZF" is lzf code copied verbatim from krita master (no linearization,
just to compare speed, not size).
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