[SOSlib-devel] variable compartment bug

[Rainer M. <ra...@tb...>]

Folks

Lukas has identified another serious bug!

SOSlib doesn't support variable compartments.

We initialize sundials with ODEs for concentrations d[A]/dt, and sundials 
calculates [A] + (d[A]/dt)*h, where h is a small time step and [A] is the 
initial condition or the current value.

If we have a variable, e.g time-dependent compartment, then d[A]/dt will 
change with changing compartment because the compartment size is part of 
the right hand side.

However, not only d[A]/dt is dependent on the volume, but also [A], i.e. 
the current value in data->value!

The attached example file exemplifies this.

So we actually should use an ODE system in amount/time instead of 
concentration/time, and have a second data->value array for concentrations 
to be used in formula evaluation.

Didn't we discuss this once? I remember that I had started to do this 
(ODEs in amount/time), but then it got more complicated then I 
thought and something else came up.

Can you think of any problems we will run into? Andrew, how about the 
compiling version?

Rainer