[Ifeffit] sum path NAN?

[Matt Newville]

Hi Mauro,

I don't know exactly what the 'sum path # # # # ' in Artemis is
supposed to display, but I'd guess that some variable or fit parameter
is being unstable.

> I've already posted this issue in a post dated 2006/10/04 and Bruce
> asked to me to give him something to reproduce this issue on his
> computer but this behavior is very unstable and I don't understand how
> to exactly reproduce it.

I think we'd need to see a project that could be made to have this
problem, even if it happens only occasionally.

> I would like to know in your opinion what could bring a variable during
> the minimization process to NAN.

Divide-by-zero and log(-1) come to mind, but I think we'd need to
determine whether a variable is being brought to NAN by the
minimization process before speculating why.

Cheers,

--Matt