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Reference Guide
exampleMultiRoot.C File Reference

Detailed Description

View in nbviewer Open in SWAN Example of using multiroot finder based on GSL algorithm.

Find the root of Rosenbrock system of equations:

\[ f1(x,y) = a(1-x) \]

\[ f2(x,y) = b(y-x^2) \]


\[ a = 1, b=10 \]

The MultiRootFinder is based on GSL and it requires the MathMore library installed


>.x exampleMultiRoot.C()


>.x exampleMultiRoot(algoname,printlevel)

where algoname is for an algorithm not using the derivatives: hybridS (default) , hybrid, dnewton, broyden

GSLMultiRootFinder::Solve:hybrids max iterations 100 and tolerance 1e-06
GSL Algorithm used is : hybrids
Number of iterations = 19
Root values = x[0] = 1 x[1] = 1
Function values = f[0] = 0 f[1] = -6.17162e-11
#include "RConfigure.h"
#error libMathMore is not available - cannot run this tutorial
#include "TF2.h"
#include "TError.h"
// example of using multi root finder based on GSL
// need to use an algorithm not requiring the derivative
//like hybrids (default), hybrid, dnewton, broyden
using namespace ROOT::Math;
void exampleMultiRoot(const char * algo = 0, int printlevel = 1) {
//defining the function
// use Rosenbrock functions
TF2 * f1 = new TF2("f1","[0]*(1-x)+[1]*y");
TF2 * f2 = new TF2("f2","[0]*(y-x*x)");
// wrap the functions
// starting point
double x0[2]={-1,-1};
ROOT::R::TRInterface & r
Definition: Object.C:4
Class for Multidimensional root finding algorithms bassed on GSL.
Class to Wrap a ROOT Function class (like TF1) in a IParamMultiFunction interface of multi-dimensions...
virtual void SetParameters(const Double_t *params)
Definition: TF1.h:644
virtual void SetParameter(Int_t param, Double_t value)
Definition: TF1.h:634
A 2-Dim function with parameters.
Definition: TF2.h:29
TF1 * f1
Definition: legend1.C:11
Lorenzo Moneta

Definition in file exampleMultiRoot.C.