Re: plzip: manual gives very false numbers, real defaults are huge!

[Antonio Diaz Diaz]

Hello Steffen,

Steffen Nurpmeso wrote:
> plzip: manual gives very false numbers, real defaults are huge!

But if you pass options to plzip (-9 -n4) then you are no longer using the 
defaults. ;-)

> but while compressing a 70MB file i realized it was not multithreaded.

At compression level 9 and 4 threads you need at least a 256 MiB file. See 
http://www.nongnu.org/lzip/manual/plzip_manual.html#Minimum-file-sizes

> (-n4 i never did; the manual however says two is default, which is
> not true, mind you)

The man page (plzip.1) is a short reference created automatically with 
help2man from 'plzip --help', and reports the number of processors in my 
machine. You need to run 'plzip --help' yourself to see the number of 
processors in your machine. The real manual can be accessed with 'info 
plzip' or at http://www.nongnu.org/lzip/manual/plzip_manual.html

> But the thing is, if i do
>
>    plzip -9 -n4 -B16000000 -c < 76-MiB-file > au.lz
>
> aka use the values the manual describes, then i get 263 and then
> 400 until the end, in my poor man's top(1).

Correct. The command above first sets a --dictionary-size of 32 MiB and a 
--data-size of 64 MiB (with -9), then reduces the --data-size to 16MB (with -B).

> Please let me make the statement that a default of 67 MiB for data
> size is really too much,

The default (if you don't specify a compression level) is 16 MiB as 
documented. If you want a high compression level without altering the 
default --dictionary-size and --data-size, you can use

  plzip -m273 -n4 -c < 76-MiB-file > au.lz

> In *my* opinion, the defaults should satisfy the occasional "i wanna
> compress something" lady (Diaz is south of Texas, is it?), instead of
> those "i want to compress my 10 GiB scientific database file" specialists.

Maybe the occasional "i wanna compress something" lady would be better 
served by using plain lzip, which compresses equally well files of any size.

About malloc, my plan is to stick to standard usage. I do not plan to play 
with it in any way.

Best regards,
Antonio.