Lzma Vs Lzma2 Vs Ppmd Vs Bzip2
Teodolinda Mattson
I do not trust non Mr. Igor 7-zip forks. Custom methods may backfire.
bzip2, if done right, it appears, is very fast and has decent compression ratio.
lzma2 on fastest settings does not saturate USB3.0 on laptop i5, even i7-4800mq
if not bzip2, deflate will be sufficient. Please bring back deflate to 7-zip GUI
2-core mobile cpu is too weak in 7-Zip.
7-Zip supports multithreading for lzma2 and bzip2.
So you can compare these methods in fast/fastest modes.
7-Zip doesn't support multithreading for deflate in 7z. So it's slow.
But 7-Zip supports some multithreading for deflate in zip.
7-Zip will use Unicode for ZIP, if you write cu in Parameters field when you create zip archive.
For some reason, "bzip2 -6" took more time than even "bzip -9". Theresult didn't change when the test was repeated. The extreme mode oflzmash creates a few bytes bigger files; seems that using "lzmash -e"makes compression both slower and less efficient with smaller files.Speed tables are omitted because the smaller test file makes measuringthe elapsed time with 'time' command too inaccurate.
In terms of speed, gzip is the winner again. lzma comes rightbehind it two to three times slower than gzip. bzip2 is a lotslower taking usually two to six times more time than lzma, that is, fourto twelve times more than gzip. One interesting thing is that gzip andlzma decompress the faster the smaller the compressed size is, whilebzip2 gets slower when the compression ratio gets better.
The memory usage of lzma stays competitive with bzip2 when files havebeen compressed with "lzmash -6" or with a smaller option. The filescompressed with the default "lzmash -7" can still be decompressed, evenon machines with only 16 MB of RAM, but sometimes you don't have eventhat much memory available. If you compress with "lzmash -8" or"lzmash -9", you should think if the users need to be able todecompress your files also on "ancient" computers.
Of course, it depends on the intended application. gzip is very fastand has small memory footprint. According to this benchmark, neitherbzip2 nor lzma can compete with gzip in terms of speed or memoryusage. bzip2 has notably better compression ratio than gzip, whichhas to be the reason for the popularity of bzip2; it is slower thangzip especially in decompression and uses more memory. However thememory requirements of bzip2 should be nowadays no problem even onolder hardware.
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