GSoC Accelerometer-based Gestures Update 3

[Koen Kooi]

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Op 15 jun 2008, om 14:51 heeft Paul-Valentin Borza het volgende  
geschreven:

> I've re-implemented hidden Markov Models. The evaluation algorithm
> Viterbi that decodes the observation sequence works perfectly.
> I've made a terrible mistake by using floats instead of doubles (I've
> used doubles on Windows) and even with scaling, to prevent underflow,
> underflow still happens.

Floating point operations are *very* slow, you can get a 50 time  
speedup by avoiding floats in your code.

> Viterbi uses float representations and logarithms and doesn't need
> scaling as underflow doesn't happen.
> Underflow happens only at the training of the gestures and I'll have
> to change the types to double.
> I've tried a different approach when I created four models, than the
> one I had on Windows, where each model used 27 states.
> The Spoken Language Processing books says that it's a better to have
> the number of states dependent of the model (on how compex the model
> gets).
> I've given some initial estimates to four models (left, right, forward
> and up) and mapped these models to actions in Amarok (next, prev,
> volumeUp and mute) with dcop.
> For example, I've modeled right with 3 states (one state is the
> initial state where you hold the Wii in your hand, the second is when
> you make your push to your right and the final state is when you stop
> moving your hand).
>
> In currently working on gesture training to change the types to
> double. Another thing I miss is Matlab (which I don't have on Ubuntu)
> and can't seem to find it anywhere.
> However, I've found Mathematica on Linux - I'm not familiar with
> Mathematica, but this one seems to have a better syntax and it draws
> antialiased plots (Matlab can't do antialias unfortunately).

Try octave.

>
>
> Everything was checked in to SVN.
>
> -- 
> http://www.borza.ro
>
>

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