Re: Bloom filters.

[Jorge <xxopxe@...>]

On 01/10/2014 02:05 PM, Philipp Janda wrote:
> > http://lua.2524044.n2.nabble.com/bloom-filter-td7611346.html
>
> A nice piece of code, actually. The bitset is a table mapping positive
> integer keys to boolean values, but instead of just using
> ...

Great explanation, thanks! Now I get it. I think I was confused by the 
"packbits" word, I thought it was some kind of RLE compression.

> Now you just need to figure out how to do a bitwise "or" of two 52-bit
> wide numbers in Lua (you can probably reuse some code from the `test`
> function) ...

I think I have some code around for bitwise operations...

> How do you hash arbitrary Lua values (e.g. tables) from within Lua? Or
> do you limit yourself to certain keys? I thought about implementing
> Bloom filters for fun not long ago, but I couldn't figure out how to
> hash a table value (or userdata, etc.) from within Lua ...

Luckily, I only have to store strings (unique identifiers). Also, out of 
lack of imagination I used CRC32 as hash function, not sure a good match.
If you need to store arbitrary data, I guess it turns into a 
serialization problem.

I uploaded my code at https://github.com/xopxe/bloomini . Notice how I 
left the lua-bloom project name available ;-)

Thanks again for the help,

Jorge