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Re: about the compression level in svndiff

From: Andreas Stieger <andreas.stieger_at_gmx.de>
Date: Mon, 15 Apr 2013 23:27:08 +0100

Hello,

On 15/04/13 23:14, Bo Chen wrote:
> SVN uses zlib to compress the new data in delta. By default, the
> compression level in the current implementation is 5, right? I am
> wondering what are differences by choosing different compression
> level? Is is a trade-off between compression rate and computational
> overhead?

Yes, obviously. Please read /usr/include/zlib.h, or anything about
compression levels?

#define Z_NO_COMPRESSION 0
#define Z_BEST_SPEED 1
#define Z_BEST_COMPRESSION 9
#define Z_DEFAULT_COMPRESSION (-1)
[...]
1 gives best speed, 9 gives best compression, 0 gives no compression at all
(the input data is simply copied a block at a time). Z_DEFAULT_COMPRESSION
requests a default compromise between speed and compression (currently
equivalent to level 6).

Andreas
Received on 2013-04-16 00:27:43 CEST

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