| Re: NaNs all over the place [message #54858 is a reply to message #54856] |
Tue, 17 July 2007 05:16  |
Conor
Messages: 138
Registered: February 2007
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Senior Member |
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On Jul 17, 7:01 am, mort canty <m.ca...@fz-juelich.de> wrote:
> OK this one is embarassing, but here goes:
>
> I've written a neural network routine in IDL which, on my laptop (XP IDL
> 6.3) chugs along just fine. On my desktop (same OS, same IDL version) it
> chugs along fine, too, but then (suddenly) slows down. Setting
> breakpoints, I find that the slowdown is due to the fact that it's
> breeding NaNs. Since IDL doesn't throw an exception, I haven't yet found
> out what's going on. Can I make IDL tell me the code line at which the
> first undefined operation generating a NaN occurs, or do I have to
> sprinkle the code with IF ~FINITE(A) - type statements?
>
> I had a similar experience long ago with Delphi (object Pascal) and it
> turned out that I was making (what else?) a pointer error. On one
> machine it didn't overwrite anything important, on the other it did and
> crashed. Is this kind of behavior even _possible_ in IDL, i.e., can
> pointer errors generate NaNs in one memory configuration and not in
> another? Or should I buy a new desktop?
>
> Any tips would be highly appreciated.
>
> Mort
Is your program generating any math errors (divide by zero or
something similar)? If it is, you can set !EXCEPT = 2 in order to see
precisely what line the math errors are occuring. If you don't have
any math errors (I'm not sure if IDL generates them when creating
NaNs. That's my only suggestion.
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