57 lines
1.2 KiB
C++
57 lines
1.2 KiB
C++
|
/*+
|
||
|
|
ARES/HADES/BORG Package -- ./libLSS/tools/bisection.hpp
|
||
|
|
Copyright (C) 2014-2020 Guilhem Lavaux <guilhem.lavaux@iap.fr>
|
||
|
|
Copyright (C) 2009-2020 Jens Jasche <jens.jasche@fysik.su.se>
|
||
|
|
|
||
|
|
Additional contributions from:
|
||
|
|
Guilhem Lavaux <guilhem.lavaux@iap.fr> (2023)
|
||
|
|
|
||
|
|
+*/
|
||
|
|
#ifndef __LIBLSS_BISECTION_HPP
|
||
|
|
#define __LIBLSS_BISECTION_HPP
|
||
|
|
|
||
|
|
#include <cmath>
|
||
|
|
|
||
|
|
namespace LibLSS {
|
||
|
|
|
||
|
|
template <typename Function>
|
||
|
|
double
|
||
|
|
bisection(double a, double b, double feps, double ftarget, Function f) {
|
||
|
|
double c = 0;
|
||
|
|
// Bisection Method
|
||
|
|
double epsilon = 1e-6;
|
||
|
|
double f_a = f(a);
|
||
|
|
double f_b = f(b);
|
||
|
|
|
||
|
|
if ((f_a < f_b && f_b < ftarget) || (f_a > f_b && f_b > ftarget)) {
|
||
|
|
return b;
|
||
|
|
}
|
||
|
|
|
||
|
|
if ((f_a < f_b && f_a > ftarget) || (f_a > f_b && f_a < ftarget)) {
|
||
|
|
return a;
|
||
|
|
}
|
||
|
|
|
||
|
|
while (std::abs(a - b) > 2 * epsilon) {
|
||
|
|
// Calculate midpoint of domain
|
||
|
|
c = (a + b) / 2.;
|
||
|
|
double f_c = f(c);
|
||
|
|
double fc = ftarget - f_c;
|
||
|
|
double fa = ftarget - f_a;
|
||
|
|
|
||
|
|
if (std::abs(fc) < feps)
|
||
|
|
break; //break if tolerance has been reached
|
||
|
|
if ((fa * fc) < 0.)
|
||
|
|
b = c;
|
||
|
|
else {
|
||
|
|
a = c;
|
||
|
|
f_a = f_c;
|
||
|
|
}
|
||
|
|
}
|
||
|
|
return c;
|
||
|
|
}
|
||
|
|
|
||
|
|
} // namespace LibLSS
|
||
|
|
|
||
|
|
#endif
|
||
|
|
|