Re: [Algorithms] sparse bitset compression

[Richard F. <ra...@gm...>]

That sounds good. Something like the JPEG VLC for the actual distance
between entries and just store deltas on a space filling curve should be
good then.


On 14 January 2014 13:11, Oscar Forth <os...@tr...>wrote:

> 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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-- 
fabs();
"The fact that an opinion has been widely held is no evidence whatever that
it is not utterly absurd." - Bertrand Russell