On Feb 14, 2007, at 12:11 , Herbert König wrote:

> Hello Bert
>
> BF> What are you using #withIndexDo: for? One third is a rather large
> BF> percentage (provided this is not an aliasing error with the
> BF> floatarray prims).
>
> First: I have an Array of Neurons and I have to train its
> neighbourhood (seen in 2D or 1D) So for every neuron I have an array
> (neighbours) pointing to its neighbours.
>
> Second: the learnrate depends on the proximity of two neurons and they
> also are stored in a precalculated array.
>
> This results in a method like:
>
> learnOneStepAtVariableRate
>         "find the neuron with the strongest reaction, train this  
> one and its
>          neighbourhood with the SOFM rule. The learning rate for  
> each neuron
>         comes from an array"
>
>         | mostExcited trainees |
>         mostExcited := outputs indexOf: outputs max.

So this goes through outputs twice ... you might add an optimized  
#indexOfMax method that does it only once.

>         trainees := neighbours at: mostExcited.
>         trainees withIndexDo:
>                         [:each :index |
>                         (neurons at: each)
>                                 sofmLearnAtLearnRate: (learnRates  
> at: index);
>                                 normalizeCoefficients]

Oh, you could use "trainees with: learnRates do: []" to avoid  
indexing by hand. Wouldn't help speed-wise of course. The only really  
fast loop is #to:do:.

Also ... why are you juggling with indices instead of putting actual  
neuron objects into the neighbors, for example? This would become

	outputs max neighbours with: learnRates do: [:neuron :rate |
		neuron sofmLearnAtLearnRate: rate;
			normalizeCoefficients]


> To get rid of a bit of this overhead in other places, I changed:
>
> "sample normalizedInputs
>         withIndexDo: [:input :indx | network inputs at: indx put:  
> input]."
>
> into:
> network inputs replaceFrom: 1  to: network inputs size with: sample  
> normalizedInputs startingAt: 1.
>
> which is a private method in FloatArray and bad style.

Actually, #replaceFrom:to:with:startingAt: is standard  
SequenceableCollection protocol, you can safely use it.

> I'm happy for every suggestion to do it speedier!
>
> If Tim reads this, I'll get scolded for premature optimisation if  
> not worse :-))

He'd be right of course ;)

- Bert -