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

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

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 }
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/