[Haskell-beginners] Avoiding stack space overflow

[David McBride]

I don't think the problem is with trainNetwork, but rather epoch.  You
might try adjusting your network datatype and sub datatypes in the manner
of data Network = Network !Int !Int until you narrow down which piece is
causing the problem.

On Mon, Jan 26, 2015 at 7:19 AM, Hans Georg Schaathun <
georg+haskell at schaathun.net> wrote:

> Hi,
>
> can someone give some hints on how to get around a stack space
> overflow?
>
> My problem is with the training function for a neural network:
>
> trainNetwork :: Double -> Samples -> Int -> Network -> Network
> trainNetwork _ _ 0 n = n
> trainNetwork eta samples c n = trainNetwork eta samples (c-1) $!
>                              epoch eta n samples
> epoch :: Double -> Network -> Samples -> Network
>
> So trainNetwork runs epoch c times, each time taking a Network
> in and modifying the Network as output.  Clearly, space complexity
> can be made constant in c, but I get stack overflow if and only
> if c is too large.
>
> As you can see, I have tried to make the epoch evaluation strict
> ($!).  I have also tried bang patterns on the input parameter n,
> and I have tried rewriting with foldr/foldl/foldl', and I have
> tried switchin the inner and outer calls (epoch vs. trainNetwork),
> all to no avail.
>
> I reckon this loop like pattern should be fairly common ...
> does it have a common solution too?
>
> TIA
> --
> :-- Hans Georg
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