[PD] SOM experts...

[zmoelnig at iem.at]

Quoting "B. Bogart" <bbogart at goto10.org>:

> Hey all, Johannes in particular,
>
> According to Medler:
> http://neuron-ai.tuke.sk/NCS/VOL1/P3_html/node28.html#SECTION00045000000000000000
>
> "...Consequently, more frequently occurring stimuli will be represented
> by larger areas in the map than infrequently occurring stimuli."
>

> If I send the same pattern to the som 10000 times, only one node will
> fire for that duration.
>
> Am I misinterpreting the text?

i think so.
[ann_som] will only output 1 winner at a time (probably it will output  
severeal winners if they all have the same distance; but i doubt  
that...)
so the neighbours of the original (and consequent) winner will adapt  
to the pattern, but they will always be a "tiny bit" less adapted than  
the winner (because originally, they were father away)
at some point, the finite precision of the numeric representation will  
eventually make the nodes _really_ equal.

> Also by default does ann_som using time-seeded random numbers or regular
> random numbers? I ask because it appears the same node always wins at
> the start... (the biggest number).

hmm, i cannot remember; i don't think that the random numbers are  
time-seeded; but most likely you can specify the seed.
you could also initialize the nodes with a constant value.
i might have a look at it within the next days.
for now, just save the SOM after initialization and compare 2 SOMs in  
your favourite numeric program....

> Is there a FANN mailinglist for the discussion of such issues?

i don't know, georg should be able to help you here.
nevertheless, bear in mind that [ann_som] is a standalone  
implementation and has nothing to do with FANN (well both are dealing  
with ann, obviously but that's it; i didn't know of fann when i wrote  
[ann_som])


mg.st
IOhannes

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