4
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:
Parameters Wall User System
-m0=LZMA -mx=9 -ms=on -mmt=off 28.4 27.48 0.85
-m1=LZMA -mx=9 -ms=on -mmt=off 27.45 33.06 0.90
-m0=LZMA -mx=9 -ms=on -mmt=on 12.74 24.39 1.14
-m1=LZMA -mx=9 -ms=on -mmt=on 15.08 33.14 1.28
-m0=LZMA -mx=9 -ms=on -mmt=off 26.5 25.58 0.65
-m1=LZMA -mx=9 -ms=on -mmt=off 27.07 32.84 0.87
-m0=LZMA -mx=9 -ms=on -mmt=on 13.27 24.99 1.00
-m1=LZMA -mx=9 -ms=on -mmt=on 15.32 33.28 1.47
Does the time to run each command replicated exactly after every run? I don't believe changing the -m0 or -m1 would make a difference as (to the best of my knowledge after reading through the 7zip documentation) the -m{n} are simply to indicate the sequence of method you use to compress, and various filters that you can apply. So the -m{n} make sense if you use more than 1 in a single command line. If you only use 1, it shouldn't make any difference. – Darius – 2013-10-25T04:47:25.917
Yep, I'd say somehow reproducible. I replaced the output with a table where I repeated the set. I noticed that with
-m1
the CPU time is more than the wall time, so there must be some multithreading at work. – AndreKR – 2013-10-25T09:07:36.400