exampleMultiRoot.C: example of using multiroot finder

// 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)
//  with 1 = 1, b=10
//
// The MultiRootFinder is based on GSL and it requires the MathMore library
// installed
//
// Usage:
//  >.x exampleMultiRoot.C()
// or
// >.x exampleMultiRoot(algoname,printlevel)
//
// where algoname is for an algorithm not using the derivatives:
//  hybridS (default) , hybrid, dnewton, broyden
//
#include "RConfigure.h"

#ifdef R__HAS_MATHMORE
#include "Math/MultiRootFinder.h"
#endif
#include "Math/WrappedMultiTF1.h"
#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) {

#ifndef R__HAS_MATHMORE
   Error("exampleMultiRoot","libMathMore is not available - cannot run this tutorial");
#else


   ROOT::Math::MultiRootFinder r(algo);
    //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)");
   f1->SetParameters(1,0);
   f2->SetParameter(0,10);
   // wrap the functions
   ROOT::Math::WrappedMultiTF1 g1(*f1,2);
   ROOT::Math::WrappedMultiTF1 g2(*f2,2);
   r.AddFunction(g1);
   r.AddFunction(g2);
   r.SetPrintLevel(printlevel);

   // starting point
   double x0[2]={-1,-1};
   r.Solve(x0);
#endif

}