# Floating point math issues

From Geos-chem

## Safe floating-point division

From http://groups.google.com/group/comp.lang.fortran/browse_thread/thread/8b367f44c419fa1d/

- Thank you to all that offered their suggestions for a "safe division" routine to prevent overflow. For those that are curious about the solution to the problem, I found useful to adopt a subroutine along the lines suggested by William Long:

if(exponent(a) - exponent (b) >= maxexponent(a) .OR. b==0)Then q=altv else q=a/b endif

- The = in the >= is to take into account the case when the fractional part of a is 1.111... and that of b is 1.

- It works very well.

- Thank you again,
- Julio.