A minimization procedure should stop when one of the following conditions is true:
The handling of these conditions is under user control. The functions below allow the user to test the precision of the current result.
This function tests the norm of the gradient g against the
absolute tolerance epsabs. The gradient of a multidimensional
function goes to zero at a minimum. The test returns
if the following condition is achieved,
|g| < epsabs
GSL_CONTINUE otherwise. A suitable choice of
epsabs can be made from the desired accuracy in the function for
small variations in x. The relationship between these quantities
is given by \delta f = g \delta x.
This function tests the minimizer specific characteristic
size (if applicable to the used minimizer) against absolute tolerance epsabs.
The test returns
GSL_SUCCESS if the size is smaller than tolerance,
GSL_CONTINUE is returned.