gsl_root_test_residual(double f, double epsabs)

[Brian Gough]

Karsten Howes writes:
 > I am working with the 1D root finder framework and I am trying to figure 
 > out how to get the value of my function at the current best root estimate 
 > (without re-evaluating my function of course).  

You do need to evaluate the function f(root).  Depending on the
algorithm it may not be a reevaluation (see e.g. bisection).

-- 
Brian Gough

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