[OSM-dev] Compression types in PBF Format

[Stefan de Konink]

On Wed, 1 Dec 2010, Anthony wrote:

> Not in an embedded system, which is where a small difference like 10%
> is going to matter.

Please elaborate? Either the memory is used for a block cache or for the 
program.


>>> I'm interested now in seeing how the full history compression goes,
>>> though.  If it can achieve 70, 80, 90% on top of zlib, then it might
>>> be worth embedding the compression as opposed to just using it for
>>> transfer over the Internet.
>>
>> The dictionary is compressed per block, so it greatly depends if the trick
>> works.
>
> 32 megs is a lot better than 900K, though.  900K is how much zlib uses, right?

I don't get your point here, what do you mean? Do you mean that the memory 
requirements for zlib is lower? Because don't forget that the extracted 
piece is kept in memory + the deserialised version. Which is basically 
much bigger right?


Stefan