[ADMB Users] eigenvectors of the Hessian and parameter errors

[dave fournier]

I sent this once but it seems to have disappeared .. so again

The error gets printed out in two cases I think.  1.) if the eigenvalues 
of the Hessian are not positive.
2) If the  std dev of a dependent variables computed by the delta method 
is not positive. However
if that parameter is not active then the message will get produced since 
its gradient is 0.
There was some attempt to make this a bit less confusing at some time, 
but maybe it died somewhere.