Re: [Genesis-sim-users] Weird arithmetic error in Genesis

[Cengiz G. <cg...@em...>]

Thanks, Dieter. I realized it must be an integer overflow after I sent out
the message.

Also the discrepancy I was working on to debug was totally my fault! :) It
turns out I missed to update the values in some compartments.

-Cengiz

On Wed, Jul 22, 2015 at 5:50 PM, Jaeger, Dieter <dj...@em...> wrote:

>  I think you overflowed your integer welcome.   If you shorten your
> numbers by a few digits you will do much better.  Of course forcing to
> float is even better.  Not sure where the digits that an int can’t hold
> actually go.  It could be bad, i.e. random memory overwrite.  -Dieter
>
>
>
> *From:* Cengiz Günay [mailto:cg...@em...]
> *Sent:* Wednesday, July 22, 2015 4:49 PM
> *To:* gen...@li...
> *Subject:* [Genesis-sim-users] Weird arithmetic error in Genesis
>
>
>
> Hi,
>
> I have been pulling my hair trying to debug arithmetic inconsistencies in
> Genesis that are caused by large truncation errors from simplest
> calculations and inconsistent PI definitions, which I realize have been
> known and we need to be cautious about. However, I wanted to report
> something really disturbing:
>
> > echo { 2012303744.1 / 3658733824.0 }
> 0.5500000385
> > echo { 2012303744.1 / 3658733824 <%203658733824> }
> 0.9370519524
>
> Does anyone have an explanation for this behavior? This can cause
> seriously wrong calculations and hidden bugs.
>
> I think the take home message is to always put a .0 behind integer numbers
> that are going to be in floating point calculations. :)
>
> Best,
>
> -Cengiz
>
> --
> Cengiz Gunay
> Postdoctoral Fellow, Dept. of Biology
> Visiting Faculty, Dept. of Math & CS
> Emory University
> http://www.biology.emory.edu/research/Prinz/Cengiz/
>