[Help-gsl] Possible multiroot shortcoming

[Mark Martin]

I've been attempting to use the multiroot facility and may have discovered an 
unpleasant feature.  The documentation states that the solvers will return an 
error code if the function or its derivative evaluate to Inf or NaN or if the 
iteration is not making progress toward a root.  However, it appears that the 
solver can also fail if it calculates some components of the approximation, 
i.e. next guess, to be NaN when it did not detect aberrant behavior in the 
function or its derivative.  The only warning that such a failure occurred is 
when the solver later indicates that it is not making progress toward a 
solution.  Unfortunately, I cannot post any reasonably simple code that 
demonstrates this problem, which is partially why I'm not submitting a formal 
bug report.  But I thought that you might want to know in case this isn't 
already a known feature.