What does the number after 7-zip's -m switch mean?

Posted by AndreKR on Super User See other posts from Super User or by AndreKR
Published on 2013-10-25T03:50:54Z Indexed on 2013/10/25 3:59 UTC
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compression

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7-zip

7-zip has a command line switch to set the compression method, -m followed by a number, e.g.
-m0=LZMA.

What does the number (0 in the example) mean? Different numbers produce slightly different compression results and performance:

time 7z -m0=LZMA -mx=9 -ms=on -mmt=off
real    0m2.292s
user    0m2.190s
sys     0m0.080s

time 7z -m1=LZMA -mx=9 -ms=on -mmt=off
real    0m2.405s
user    0m3.240s
sys     0m0.070s

time 7z -m0=LZMA -mx=9 -ms=on -mmt=on
real    0m1.038s
user    0m1.920s
sys     0m0.150s

time 7z -m1=LZMA -mx=9 -ms=on -mmt=on
real    0m1.187s
user    0m2.800s
sys     0m0.130s

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