Hello Mark,
[email protected] wrote:
lzip's initial memory check seems to be too conservative. Or does lzip
uses more memory than xz and lzma_alone with the same dictionary size?
IIRC lzip 1.11 does use a few MB more than lzma-utils for the same
dictionary size. I don't know the amount used by other lzma_alone
implementations.
Lzip 1.11 does not perform any memory check. It tries to assign the
needed memory, and if it can't, it prints the "Not enough memory. Try a
smaller dictionary size." message. I think xz does perform a memory
check and adjusts the dictionary size accordingly.
From http://www.nongnu.org/lzip/manual/lzip_manual.html#Introduction
"The amount of memory required for compression is about 5 MiB plus 1 or
2 times the dictionary size limit (1 if input file size is less than
dictionary size limit, else 2) plus 8 times the dictionary size really
used. The option `-0' is special and only requires about 1.5 MiB at most."
So for that specific file, lzip took about 2.5 times as long as xz.
I guess your system is swapping slightly because of the large dictionary
size. As you can see, for example here[1], lzip and xz are comparable
both in compression time and size, with "lzip -9" tending to be slower
than "xz -9" but compressing a little more.
[1] http://martin-steigerwald.de/computer/programme/packbench/index.html
Any idea what causes the time difference? Could
different compiler options have that large an effect? I think I compiled
xz with -O3 but lzip with -O2.
I have only noticed small speed changes in lzip between -O2 and -O3. I
don't know the effects on xz, but I don't think they can be so large.
Regards,
Antonio.
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