Hi,
Sure:
The data is a 3d medical image, however we are only interested in a part of
it (say the skeleton). Usually a medical
image has 3 dimensions (x, y, z), and there are nx, ny, nz pixels in each
dimension. We only
wish to store information about the skeletal voxels, as this might make up
only 10% of the volume of the whole
scan.
Each of these voxels will have a 3d index (x, y, z) which gets mapped to 1d
(using say row major order idx1d = z*nx*ny + y*nx + x).
Thus we store only the 1d indexes in sequential order, and any associated
data arrays.
So
idx1d.at(0) = 1001 (say)
idx1d.at(1) = 1005
idx1d.at(2) = 1017
idx1d.at(3) = 1021
.
.
But we need to invert this array in order to do certain operations on the
data, which is where Judy
comes in (or a hash table, or whatever). In terms of memory used, I am
usually indexing between 3-15 million
numbers.
The CPU is an Intel Quad core machine, Q6600, 2.4GHz, 2.75 GB of memory. Not
sure about
cache and stuff.
Note that in the run times most of the computation is doing lots of math
stuff, so its not a direct comparison,
however I think its quite 'real world'
About using gcc - I would prefer to do that too, and be working on a Linux
machine, however the
company I'm developing the code for is a Microsoft shop, so I'm stuck with
it :-((
2009/3/17 zooko <[email protected]>
> On Mar 17, 2009, at 8:19 AM, Richard Boyes wrote:
>
> The headline results were that the Judy array used ~1/4 - 1/3rd of the
>> memory of my hash table (which had a load of about 50%), while there was a
>> slight improvement in the speed (average hash run time = x, average judy run
>> time = y), which was statistically significant in a t-test.
>>
>
> Sweet! Have you written down more details that others can read?
>
> I don't have experience building Judy on Windows, but I have the following
> comments:
>
> 1. I don't think it should matter which compiler was used to generate
> JudyLTablesGen (but I'm not sure).
> 2. Why not just use gcc everywhere instead of the Microsoft compiler? :-)
>
> Regards,
>
> Zooko
> ---
> Tahoe, the Least-Authority Filesystem -- http://allmydata.org
> store your data: $10/month -- http://allmydata.com/?tracking=zsig
>
>
--
Richard
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