I think we'll continue to find improvements in the optimal parsers over the coming months (optimal parsing is hard!) which should lead to some more tiny gains in the compression ratio in the slow encoder modes.
Silesia , sum of all files
uncompressed : 211,938,580
Kraken 2.1.5 -z6 : 52,366,897
Kraken 2.2.0 -z6 : 51,857,427
Kraken 2.2.0 -z7 : 51,625,488
Oodle Kraken 2.1.5 topped out at -z6 (Optimal2). There's a new -z7 (Optimal3) mode which gets a bit
more compression at the cost of a bit of speed,
which is why it's on a separate option instead of just part of -z6.
Results on some individual files (Kraken 220 is -z7) :
-------------------------------------------------------
"silesia_mozilla"
by ratio:
lzma : 3.88:1 , 2.0 enc mb/s , 63.7 dec mb/s
Kraken 220 : 3.60:1 , 1.1 enc mb/s , 896.5 dec mb/s
lzham : 3.56:1 , 1.5 enc mb/s , 186.4 dec mb/s
Kraken 215 : 3.51:1 , 1.2 enc mb/s , 928.0 dec mb/s
zstdmax : 3.24:1 , 2.8 enc mb/s , 401.0 dec mb/s
zlib9 : 2.51:1 , 12.4 enc mb/s , 291.5 dec mb/s
lz4hc : 2.32:1 , 36.4 enc mb/s , 2351.6 dec mb/s
-------------------------------------------------------
"lzt99"
by ratio:
lzma : 2.65:1 , 3.1 enc mb/s , 42.3 dec mb/s
Kraken 220 : 2.53:1 , 2.0 enc mb/s , 912.0 dec mb/s
Kraken 215 : 2.46:1 , 2.3 enc mb/s , 957.1 dec mb/s
lzham : 2.44:1 , 1.9 enc mb/s , 166.0 dec mb/s
zstdmax : 2.27:1 , 3.8 enc mb/s , 482.3 dec mb/s
zlib9 : 1.77:1 , 13.3 enc mb/s , 286.2 dec mb/s
lz4hc : 1.67:1 , 30.3 enc mb/s , 2737.4 dec mb/s
-------------------------------------------------------
"all_dds"
by ratio:
lzma : 2.37:1 , 2.1 enc mb/s , 40.8 dec mb/s
Kraken 220 : 2.23:1 , 1.0 enc mb/s , 650.6 dec mb/s
Kraken 215 : 2.18:1 , 1.0 enc mb/s , 684.6 dec mb/s
lzham : 2.17:1 , 1.3 enc mb/s , 127.7 dec mb/s
zstdmax : 2.02:1 , 3.3 enc mb/s , 289.4 dec mb/s
zlib9 : 1.83:1 , 13.3 enc mb/s , 242.9 dec mb/s
lz4hc : 1.67:1 , 20.4 enc mb/s , 2226.9 dec mb/s
-------------------------------------------------------
"baby_robot_shell.gr2"
by ratio:
lzma : 4.35:1 , 3.1 enc mb/s , 59.3 dec mb/s
Kraken 220 : 3.82:1 , 1.4 enc mb/s , 837.2 dec mb/s
Kraken 215 : 3.77:1 , 1.5 enc mb/s , 878.3 dec mb/s
lzham : 3.77:1 , 1.6 enc mb/s , 162.5 dec mb/s
zstdmax : 2.77:1 , 5.7 enc mb/s , 405.7 dec mb/s
zlib9 : 2.19:1 , 13.9 enc mb/s , 332.9 dec mb/s
lz4hc : 1.78:1 , 40.1 enc mb/s , 2364.4 dec mb
-------------------------------------------------------
"win81"
by ratio:
lzma : 2.95:1 , 2.5 enc mb/s , 51.9 dec mb/s
lzham : 2.77:1 , 1.6 enc mb/s , 177.6 dec mb/s
Kraken 220 : 2.77:1 , 1.0 enc mb/s , 818.0 dec mb/s
Kraken 215 : 2.70:1 , 1.0 enc mb/s , 877.0 dec mb/s
zstdmax : 2.64:1 , 3.5 enc mb/s , 417.8 dec mb/s
zlib9 : 2.07:1 , 16.8 enc mb/s , 269.6 dec mb/s
lz4hc : 1.91:1 , 28.8 enc mb/s , 2297.6 dec mb/s
-------------------------------------------------------
"enwik7"
by ratio:
lzma : 3.64:1 , 1.8 enc mb/s , 79.5 dec mb/s
lzham : 3.60:1 , 1.4 enc mb/s , 196.5 dec mb/s
zstdmax : 3.56:1 , 2.2 enc mb/s , 394.6 dec mb/s
Kraken 220 : 3.51:1 , 1.4 enc mb/s , 702.8 dec mb/s
Kraken 215 : 3.49:1 , 1.5 enc mb/s , 789.7 dec mb/s
zlib9 : 2.38:1 , 22.2 enc mb/s , 234.3 dec mb/s
lz4hc : 2.35:1 , 27.5 enc mb/s , 2059.6 dec mb/s
-------------------------------------------------------
You can see that encode & decode speed is slightly worse at level -z7 , and compression ratio si
improved. (most of the other compression levels have roughly the same decode speed; -z7 enables
some special options that can hurt decode speed a bit). Of course even at -z7 Kraken is way faster
than anything else comparable!
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