Re: [Algorithms] sparse bitset compression

[Oscar F. <os...@tr...>]

Just a random though, so apologies if i'm talking about my arse, but ...
couldn't you just use something like the bit plane compression from Wavelet
Difference Reduction (WDR)?

A lot depends on your data, I appreciate, so this may not work out as any
significant saving ...

I wrote about the compression method in my blog a few years back:

http://trueharmoniccolours.co.uk/Blog/?p=55

Obviously thats in the context of a full wavelet image compressor so you
will have to just grab the part I explain in the link above.

Also apologies for the code formatting on my blog ... ill fix it one day ;)

Oscar

On 14 January 2014 12:37, Richard Fabian <ra...@gm...> wrote:

> The web is full of different solutions for compressing things, but some of
> you have probably already done this and found a really good ratio
> compression scheme that fits what I'm asking about.
>
> I've got a load of entites, (4-7k) that live on a grid (1024x1024), and I
> need to persist them to a savegame which gets sent across the network to
> keep the save safe. I need to compress it. I'm compressing the entities in
> the world already, ones that have been affected cost a few bytes, but the
> but for the ones that don't have any changes, all I'm left with is the
> coords. There are only a few that need the fatter compression, but at the
> numbers I'm looking at, those "unchanged entity" coords add up to a lot of
> data when storing as 20 bit structs. This is too much for sending over the
> network regularly as part of a save.
>
> I've had some ideas on how to compress the data, but they might be crap. I
> don't know.
>
> I can't easily regenerate the set so thought someone who wanted to
> compress consumables might know the name of a good solution for sparse
> bitset compression. The bits are clumped around different areas of the
> grid, so I feel that something that leverages spatial coherence might do
> well.
>
> Any leads would be highly appreciated.
>
> --
> fabs();
> "The fact that an opinion has been widely held is no evidence whatever
> that it is not utterly absurd." - Bertrand Russell
>
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