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Does KGB Archiver really achieve high compression rates?

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Eóin:
I came across KGB Archiver a while back and really don't know what to make of it.

KGB Archiver is the compression tool with an unbelievably high compression rate. Unfortunately, in spite of its powerful compression rate, it has high hardware requirements (I recommend processor with 1,5GHz clock and 256MB of RAM as an essential minimum). One of the advantages of KGB Archiver is also AES-256 encryption which is used to encrypt the archives. This is one of the strongest encryptions known for human.-http://kgbarchiver.net/
--- End quote ---

Initially I ran a simple test against 7 zip on a small source bundle, it failed miserably but I hadn't used to highest compression so didn't want to discount it nor can I remember to exact figures to post here. Now I have run a second test and it once again it seriously disappoints.

I compressed a VirtualBox VDI (virtual disk image) file of a Server 2008 install. That's 5.8 GB uncompressed. I think these figures speak for themselves.
7 zip (ultra compression)984 MB~45minsKGB Archiver (highest settings)1.19GB~16hrs 30mins
Is it all a scam or have I just happened to pick two very difficult test cases?

mwb1100:
I haven't tried KGB (or even downloaded it), but it seems harsh to even remotely call it a 'scam'.

It's an open-source project that makes some impressive claims about it's compression ratios.  While it might not work as well in your tests as the claims suggest - indeed it may not even be suitable for use (16 hours is a long time to spend compressing) - I think that applying the term 'scam' to software should be reserved for things involving malware or fraud. It should not be used in a situation where a compression utility doesn't perform quite as well as another.

Renegade:
It's using different PAQ flavours for compression...

They are NOT CPU friendly in the least. They are extremely slow, but they do get better compression than pretty much anything else (in general that is). Check out Maximum Compression. You'll see that PAQ compression schemes are always among the top.

PAQ is inefficient and at maximum settings, almost unusable for anything but very small archives. As you have seen with a 16+ hour go at it for 5.8GB of data. Not fun.

Efficiency becomes more important (for humans) with larger archives.

Renegade:
Check out the multi-file compression test at Maximum Compression.

PAQ8O8 at the top takes 43,660 seconds. That's 12 hours, 7 minutes, 40 seconds. Scroll down and you'll see ALZip does ALZ compression in 36 seconds. BIG difference.

Then again, ALZ gets 63% compression, while PAQ8O8 gets 80% -- 17% more, but at a cost of an additional 12 hours, 7 minutes, 4 seconds.

Different formats have different strengths. It's best to know what you're doing when you choose a format. If not, just go for ZIP compression.

Eóin:
I used the word scam because I heard about it on forums with claims of near 1% compression ratios. But in fairness those claims were being made by others, it's own website doesn't make such a claim so I've changed the title of the thread as to not imply deceit on the developers part.

I can imagine an excellent compression ratio even at the expense of seriously heavy cpu costs could be justified if the compression is a one time cost. Say in distributing large downloads, the bandwidth saving could justify the initial compression investment.

But given that in both my tests it underperformed 7 zip even before taking time into account I wondered was it not all it seemed to be :huh:

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