// This file is part of Eigen, a lightweight C++ template library
// for linear algebra.
//
// Copyright (C) 2009 Thomas Capricelli <orzel@freehackers.org>
// Copyright (C) 2012 desire Nuentsa <desire.nuentsa_wakam@inria.fr
//
// This Source Code Form is subject to the terms of the Mozilla
// Public License v. 2.0. If a copy of the MPL was not distributed
// with this file, You can obtain one at http://mozilla.org/MPL/2.0/.


#include <stdio.h>

#include "main.h"
#include <Eigen/LevenbergMarquardt>

// This disables some useless Warnings on MSVC.
// It is intended to be done for this test only.
#include <Eigen/src/Core/util/DisableStupidWarnings.h>

using std::sqrt;

struct lmder_functor : DenseFunctor<double>
{
    lmder_functor(void): DenseFunctor<double>(3,15) {}
    int operator()(const VectorXd &x, VectorXd &fvec) const
    {
        double tmp1, tmp2, tmp3;
        static const double y[15] = {1.4e-1, 1.8e-1, 2.2e-1, 2.5e-1, 2.9e-1, 3.2e-1, 3.5e-1,
            3.9e-1, 3.7e-1, 5.8e-1, 7.3e-1, 9.6e-1, 1.34, 2.1, 4.39};

        for (int i = 0; i < values(); i++)
        {
            tmp1 = i+1;
            tmp2 = 16 - i - 1;
            tmp3 = (i>=8)? tmp2 : tmp1;
            fvec[i] = y[i] - (x[0] + tmp1/(x[1]*tmp2 + x[2]*tmp3));
        }
        return 0;
    }

    int df(const VectorXd &x, MatrixXd &fjac) const
    {
        double tmp1, tmp2, tmp3, tmp4;
        for (int i = 0; i < values(); i++)
        {
            tmp1 = i+1;
            tmp2 = 16 - i - 1;
            tmp3 = (i>=8)? tmp2 : tmp1;
            tmp4 = (x[1]*tmp2 + x[2]*tmp3); tmp4 = tmp4*tmp4;
            fjac(i,0) = -1;
            fjac(i,1) = tmp1*tmp2/tmp4;
            fjac(i,2) = tmp1*tmp3/tmp4;
        }
        return 0;
    }
};

void testLmder1()
{
  int n=3, info;

  VectorXd x;

  /* the following starting values provide a rough fit. */
  x.setConstant(n, 1.);

  // do the computation
  lmder_functor functor;
  LevenbergMarquardt<lmder_functor> lm(functor);
  info = lm.lmder1(x);

  // check return value
  VERIFY_IS_EQUAL(info, 1);
  VERIFY_IS_EQUAL(lm.nfev(), 6);
  VERIFY_IS_EQUAL(lm.njev(), 5);

  // check norm
  VERIFY_IS_APPROX(lm.fvec().blueNorm(), 0.09063596);

  // check x
  VectorXd x_ref(n);
  x_ref << 0.08241058, 1.133037, 2.343695;
  VERIFY_IS_APPROX(x, x_ref);
}

void testLmder()
{
  const int m=15, n=3;
  int info;
  double fnorm, covfac;
  VectorXd x;

  /* the following starting values provide a rough fit. */
  x.setConstant(n, 1.);

  // do the computation
  lmder_functor functor;
  LevenbergMarquardt<lmder_functor> lm(functor);
  info = lm.minimize(x);

  // check return values
  VERIFY_IS_EQUAL(info, 1);
  VERIFY_IS_EQUAL(lm.nfev(), 6);
  VERIFY_IS_EQUAL(lm.njev(), 5);

  // check norm
  fnorm = lm.fvec().blueNorm();
  VERIFY_IS_APPROX(fnorm, 0.09063596);

  // check x
  VectorXd x_ref(n);
  x_ref << 0.08241058, 1.133037, 2.343695;
  VERIFY_IS_APPROX(x, x_ref);

  // check covariance
  covfac = fnorm*fnorm/(m-n);
  internal::covar(lm.fjac(), lm.permutation().indices()); // TODO : move this as a function of lm

  MatrixXd cov_ref(n,n);
  cov_ref <<
      0.0001531202,   0.002869941,  -0.002656662,
      0.002869941,    0.09480935,   -0.09098995,
      -0.002656662,   -0.09098995,    0.08778727;

//  std::cout << fjac*covfac << std::endl;

  MatrixXd cov;
  cov =  covfac*lm.fjac().topLeftCorner<n,n>();
  VERIFY_IS_APPROX( cov, cov_ref);
  // TODO: why isn't this allowed ? :
  // VERIFY_IS_APPROX( covfac*fjac.topLeftCorner<n,n>() , cov_ref);
}

struct lmdif_functor : DenseFunctor<double>
{
    lmdif_functor(void) : DenseFunctor<double>(3,15) {}
    int operator()(const VectorXd &x, VectorXd &fvec) const
    {
        int i;
        double tmp1,tmp2,tmp3;
        static const double y[15]={1.4e-1,1.8e-1,2.2e-1,2.5e-1,2.9e-1,3.2e-1,3.5e-1,3.9e-1,
            3.7e-1,5.8e-1,7.3e-1,9.6e-1,1.34e0,2.1e0,4.39e0};

        assert(x.size()==3);
        assert(fvec.size()==15);
        for (i=0; i<15; i++)
        {
            tmp1 = i+1;
            tmp2 = 15 - i;
            tmp3 = tmp1;

            if (i >= 8) tmp3 = tmp2;
            fvec[i] = y[i] - (x[0] + tmp1/(x[1]*tmp2 + x[2]*tmp3));
        }
        return 0;
    }
};

void testLmdif1()
{
  const int n=3;
  int info;

  VectorXd x(n), fvec(15);

  /* the following starting values provide a rough fit. */
  x.setConstant(n, 1.);

  // do the computation
  lmdif_functor functor;
  DenseIndex nfev;
  info = LevenbergMarquardt<lmdif_functor>::lmdif1(functor, x, &nfev);

  // check return value
  VERIFY_IS_EQUAL(info, 1);
  VERIFY_IS_EQUAL(nfev, 26);

  // check norm
  functor(x, fvec);
  VERIFY_IS_APPROX(fvec.blueNorm(), 0.09063596);

  // check x
  VectorXd x_ref(n);
  x_ref << 0.0824106, 1.1330366, 2.3436947;
  VERIFY_IS_APPROX(x, x_ref);

}

void testLmdif()
{
  const int m=15, n=3;
  int info;
  double fnorm, covfac;
  VectorXd x(n);

  /* the following starting values provide a rough fit. */
  x.setConstant(n, 1.);

  // do the computation
  lmdif_functor functor;
  NumericalDiff<lmdif_functor> numDiff(functor);
  LevenbergMarquardt<NumericalDiff<lmdif_functor> > lm(numDiff);
  info = lm.minimize(x);

  // check return values
  VERIFY_IS_EQUAL(info, 1);
  VERIFY_IS_EQUAL(lm.nfev(), 26);

  // check norm
  fnorm = lm.fvec().blueNorm();
  VERIFY_IS_APPROX(fnorm, 0.09063596);

  // check x
  VectorXd x_ref(n);
  x_ref << 0.08241058, 1.133037, 2.343695;
  VERIFY_IS_APPROX(x, x_ref);

  // check covariance
  covfac = fnorm*fnorm/(m-n);
  internal::covar(lm.fjac(), lm.permutation().indices()); // TODO : move this as a function of lm

  MatrixXd cov_ref(n,n);
  cov_ref <<
      0.0001531202,   0.002869942,  -0.002656662,
      0.002869942,    0.09480937,   -0.09098997,
      -0.002656662,   -0.09098997,    0.08778729;

//  std::cout << fjac*covfac << std::endl;

  MatrixXd cov;
  cov =  covfac*lm.fjac().topLeftCorner<n,n>();
  VERIFY_IS_APPROX( cov, cov_ref);
  // TODO: why isn't this allowed ? :
  // VERIFY_IS_APPROX( covfac*fjac.topLeftCorner<n,n>() , cov_ref);
}

struct chwirut2_functor : DenseFunctor<double>
{
    chwirut2_functor(void) : DenseFunctor<double>(3,54) {}
    static const double m_x[54];
    static const double m_y[54];
    int operator()(const VectorXd &b, VectorXd &fvec)
    {
        int i;

        assert(b.size()==3);
        assert(fvec.size()==54);
        for(i=0; i<54; i++) {
            double x = m_x[i];
            fvec[i] = exp(-b[0]*x)/(b[1]+b[2]*x) - m_y[i];
        }
        return 0;
    }
    int df(const VectorXd &b, MatrixXd &fjac)
    {
        assert(b.size()==3);
        assert(fjac.rows()==54);
        assert(fjac.cols()==3);
        for(int i=0; i<54; i++) {
            double x = m_x[i];
            double factor = 1./(b[1]+b[2]*x);
            double e = exp(-b[0]*x);
            fjac(i,0) = -x*e*factor;
            fjac(i,1) = -e*factor*factor;
            fjac(i,2) = -x*e*factor*factor;
        }
        return 0;
    }
};
const double chwirut2_functor::m_x[54] = { 0.500E0, 1.000E0, 1.750E0, 3.750E0, 5.750E0, 0.875E0, 2.250E0, 3.250E0, 5.250E0, 0.750E0, 1.750E0, 2.750E0, 4.750E0, 0.625E0, 1.250E0, 2.250E0, 4.250E0, .500E0, 3.000E0, .750E0, 3.000E0, 1.500E0, 6.000E0, 3.000E0, 6.000E0, 1.500E0, 3.000E0, .500E0, 2.000E0, 4.000E0, .750E0, 2.000E0, 5.000E0, .750E0, 2.250E0, 3.750E0, 5.750E0, 3.000E0, .750E0, 2.500E0, 4.000E0, .750E0, 2.500E0, 4.000E0, .750E0, 2.500E0, 4.000E0, .500E0, 6.000E0, 3.000E0, .500E0, 2.750E0, .500E0, 1.750E0};
const double chwirut2_functor::m_y[54] = { 92.9000E0 ,57.1000E0 ,31.0500E0 ,11.5875E0 ,8.0250E0 ,63.6000E0 ,21.4000E0 ,14.2500E0 ,8.4750E0 ,63.8000E0 ,26.8000E0 ,16.4625E0 ,7.1250E0 ,67.3000E0 ,41.0000E0 ,21.1500E0 ,8.1750E0 ,81.5000E0 ,13.1200E0 ,59.9000E0 ,14.6200E0 ,32.9000E0 ,5.4400E0 ,12.5600E0 ,5.4400E0 ,32.0000E0 ,13.9500E0 ,75.8000E0 ,20.0000E0 ,10.4200E0 ,59.5000E0 ,21.6700E0 ,8.5500E0 ,62.0000E0 ,20.2000E0 ,7.7600E0 ,3.7500E0 ,11.8100E0 ,54.7000E0 ,23.7000E0 ,11.5500E0 ,61.3000E0 ,17.7000E0 ,8.7400E0 ,59.2000E0 ,16.3000E0 ,8.6200E0 ,81.0000E0 ,4.8700E0 ,14.6200E0 ,81.7000E0 ,17.1700E0 ,81.3000E0 ,28.9000E0  };

// http://www.itl.nist.gov/div898/strd/nls/data/chwirut2.shtml
void testNistChwirut2(void)
{
  const int n=3;
  int info;

  VectorXd x(n);

  /*
   * First try
   */
  x<< 0.1, 0.01, 0.02;
  // do the computation
  chwirut2_functor functor;
  LevenbergMarquardt<chwirut2_functor> lm(functor);
  info = lm.minimize(x);

  // check return value
  VERIFY_IS_EQUAL(info, 1);
  VERIFY_IS_EQUAL(lm.nfev(), 10);
  VERIFY_IS_EQUAL(lm.njev(), 8);
  // check norm^2
  VERIFY_IS_APPROX(lm.fvec().squaredNorm(), 5.1304802941E+02);
  // check x
  VERIFY_IS_APPROX(x[0], 1.6657666537E-01);
  VERIFY_IS_APPROX(x[1], 5.1653291286E-03);
  VERIFY_IS_APPROX(x[2], 1.2150007096E-02);

  /*
   * Second try
   */
  x<< 0.15, 0.008, 0.010;
  // do the computation
  lm.resetParameters();
  lm.setFtol(1.E6*NumTraits<double>::epsilon());
  lm.setXtol(1.E6*NumTraits<double>::epsilon());
  info = lm.minimize(x);

  // check return value
  VERIFY_IS_EQUAL(info, 1);
  VERIFY_IS_EQUAL(lm.nfev(), 7);
  VERIFY_IS_EQUAL(lm.njev(), 6);
  // check norm^2
  VERIFY_IS_APPROX(lm.fvec().squaredNorm(), 5.1304802941E+02);
  // check x
  VERIFY_IS_APPROX(x[0], 1.6657666537E-01);
  VERIFY_IS_APPROX(x[1], 5.1653291286E-03);
  VERIFY_IS_APPROX(x[2], 1.2150007096E-02);
}


struct misra1a_functor : DenseFunctor<double>
{
    misra1a_functor(void) : DenseFunctor<double>(2,14) {}
    static const double m_x[14];
    static const double m_y[14];
    int operator()(const VectorXd &b, VectorXd &fvec)
    {
        assert(b.size()==2);
        assert(fvec.size()==14);
        for(int i=0; i<14; i++) {
            fvec[i] = b[0]*(1.-exp(-b[1]*m_x[i])) - m_y[i] ;
        }
        return 0;
    }
    int df(const VectorXd &b, MatrixXd &fjac)
    {
        assert(b.size()==2);
        assert(fjac.rows()==14);
        assert(fjac.cols()==2);
        for(int i=0; i<14; i++) {
            fjac(i,0) = (1.-exp(-b[1]*m_x[i]));
            fjac(i,1) = (b[0]*m_x[i]*exp(-b[1]*m_x[i]));
        }
        return 0;
    }
};
const double misra1a_functor::m_x[14] = { 77.6E0, 114.9E0, 141.1E0, 190.8E0, 239.9E0, 289.0E0, 332.8E0, 378.4E0, 434.8E0, 477.3E0, 536.8E0, 593.1E0, 689.1E0, 760.0E0};
const double misra1a_functor::m_y[14] = { 10.07E0, 14.73E0, 17.94E0, 23.93E0, 29.61E0, 35.18E0, 40.02E0, 44.82E0, 50.76E0, 55.05E0, 61.01E0, 66.40E0, 75.47E0, 81.78E0};

// http://www.itl.nist.gov/div898/strd/nls/data/misra1a.shtml
void testNistMisra1a(void)
{
  const int n=2;
  int info;

  VectorXd x(n);

  /*
   * First try
   */
  x<< 500., 0.0001;
  // do the computation
  misra1a_functor functor;
  LevenbergMarquardt<misra1a_functor> lm(functor);
  info = lm.minimize(x);

  // check return value
  VERIFY_IS_EQUAL(info, 1);
  VERIFY_IS_EQUAL(lm.nfev(), 19);
  VERIFY_IS_EQUAL(lm.njev(), 15);
  // check norm^2
  VERIFY_IS_APPROX(lm.fvec().squaredNorm(), 1.2455138894E-01);
  // check x
  VERIFY_IS_APPROX(x[0], 2.3894212918E+02);
  VERIFY_IS_APPROX(x[1], 5.5015643181E-04);

  /*
   * Second try
   */
  x<< 250., 0.0005;
  // do the computation
  info = lm.minimize(x);

  // check return value
  VERIFY_IS_EQUAL(info, 1);
  VERIFY_IS_EQUAL(lm.nfev(), 5);
  VERIFY_IS_EQUAL(lm.njev(), 4);
  // check norm^2
  VERIFY_IS_APPROX(lm.fvec().squaredNorm(), 1.2455138894E-01);
  // check x
  VERIFY_IS_APPROX(x[0], 2.3894212918E+02);
  VERIFY_IS_APPROX(x[1], 5.5015643181E-04);
}

struct hahn1_functor : DenseFunctor<double>
{
    hahn1_functor(void) : DenseFunctor<double>(7,236) {}
    static const double m_x[236];
    int operator()(const VectorXd &b, VectorXd &fvec)
    {
        static const double m_y[236] = { .591E0 , 1.547E0 , 2.902E0 , 2.894E0 , 4.703E0 , 6.307E0 , 7.03E0  , 7.898E0 , 9.470E0 , 9.484E0 , 10.072E0 , 10.163E0 , 11.615E0 , 12.005E0 , 12.478E0 , 12.982E0 , 12.970E0 , 13.926E0 , 14.452E0 , 14.404E0 , 15.190E0 , 15.550E0 , 15.528E0 , 15.499E0 , 16.131E0 , 16.438E0 , 16.387E0 , 16.549E0 , 16.872E0 , 16.830E0 , 16.926E0 , 16.907E0 , 16.966E0 , 17.060E0 , 17.122E0 , 17.311E0 , 17.355E0 , 17.668E0 , 17.767E0 , 17.803E0 , 17.765E0 , 17.768E0 , 17.736E0 , 17.858E0 , 17.877E0 , 17.912E0 , 18.046E0 , 18.085E0 , 18.291E0 , 18.357E0 , 18.426E0 , 18.584E0 , 18.610E0 , 18.870E0 , 18.795E0 , 19.111E0 , .367E0 , .796E0 , 0.892E0 , 1.903E0 , 2.150E0 , 3.697E0 , 5.870E0 , 6.421E0 , 7.422E0 , 9.944E0 , 11.023E0 , 11.87E0  , 12.786E0 , 14.067E0 , 13.974E0 , 14.462E0 , 14.464E0 , 15.381E0 , 15.483E0 , 15.59E0  , 16.075E0 , 16.347E0 , 16.181E0 , 16.915E0 , 17.003E0 , 16.978E0 , 17.756E0 , 17.808E0 , 17.868E0 , 18.481E0 , 18.486E0 , 19.090E0 , 16.062E0 , 16.337E0 , 16.345E0 ,
        16.388E0 , 17.159E0 , 17.116E0 , 17.164E0 , 17.123E0 , 17.979E0 , 17.974E0 , 18.007E0 , 17.993E0 , 18.523E0 , 18.669E0 , 18.617E0 , 19.371E0 , 19.330E0 , 0.080E0 , 0.248E0 , 1.089E0 , 1.418E0 , 2.278E0 , 3.624E0 , 4.574E0 , 5.556E0 , 7.267E0 , 7.695E0 , 9.136E0 , 9.959E0 , 9.957E0 , 11.600E0 , 13.138E0 , 13.564E0 , 13.871E0 , 13.994E0 , 14.947E0 , 15.473E0 , 15.379E0 , 15.455E0 , 15.908E0 , 16.114E0 , 17.071E0 , 17.135E0 , 17.282E0 , 17.368E0 , 17.483E0 , 17.764E0 , 18.185E0 , 18.271E0 , 18.236E0 , 18.237E0 , 18.523E0 , 18.627E0 , 18.665E0 , 19.086E0 , 0.214E0 , 0.943E0 , 1.429E0 , 2.241E0 , 2.951E0 , 3.782E0 , 4.757E0 , 5.602E0 , 7.169E0 , 8.920E0 , 10.055E0 , 12.035E0 , 12.861E0 , 13.436E0 , 14.167E0 , 14.755E0 , 15.168E0 , 15.651E0 , 15.746E0 , 16.216E0 , 16.445E0 , 16.965E0 , 17.121E0 , 17.206E0 , 17.250E0 , 17.339E0 , 17.793E0 , 18.123E0 , 18.49E0  , 18.566E0 , 18.645E0 , 18.706E0 , 18.924E0 , 19.1E0   , 0.375E0 , 0.471E0 , 1.504E0 , 2.204E0 , 2.813E0 , 4.765E0 , 9.835E0 , 10.040E0 , 11.946E0 , 
12.596E0 , 
13.303E0 , 13.922E0 , 14.440E0 , 14.951E0 , 15.627E0 , 15.639E0 , 15.814E0 , 16.315E0 , 16.334E0 , 16.430E0 , 16.423E0 , 17.024E0 , 17.009E0 , 17.165E0 , 17.134E0 , 17.349E0 , 17.576E0 , 17.848E0 , 18.090E0 , 18.276E0 , 18.404E0 , 18.519E0 , 19.133E0 , 19.074E0 , 19.239E0 , 19.280E0 , 19.101E0 , 19.398E0 , 19.252E0 , 19.89E0  , 20.007E0 , 19.929E0 , 19.268E0 , 19.324E0 , 20.049E0 , 20.107E0 , 20.062E0 , 20.065E0 , 19.286E0 , 19.972E0 , 20.088E0 , 20.743E0 , 20.83E0  , 20.935E0 , 21.035E0 , 20.93E0  , 21.074E0 , 21.085E0 , 20.935E0 };

        //        int called=0; printf("call hahn1_functor with  iflag=%d, called=%d\n", iflag, called); if (iflag==1) called++;

        assert(b.size()==7);
        assert(fvec.size()==236);
        for(int i=0; i<236; i++) {
            double x=m_x[i], xx=x*x, xxx=xx*x;
            fvec[i] = (b[0]+b[1]*x+b[2]*xx+b[3]*xxx) / (1.+b[4]*x+b[5]*xx+b[6]*xxx) - m_y[i];
        }
        return 0;
    }

    int df(const VectorXd &b, MatrixXd &fjac)
    {
        assert(b.size()==7);
        assert(fjac.rows()==236);
        assert(fjac.cols()==7);
        for(int i=0; i<236; i++) {
            double x=m_x[i], xx=x*x, xxx=xx*x;
            double fact = 1./(1.+b[4]*x+b[5]*xx+b[6]*xxx);
            fjac(i,0) = 1.*fact;
            fjac(i,1) = x*fact;
            fjac(i,2) = xx*fact;
            fjac(i,3) = xxx*fact;
            fact = - (b[0]+b[1]*x+b[2]*xx+b[3]*xxx) * fact * fact;
            fjac(i,4) = x*fact;
            fjac(i,5) = xx*fact;
            fjac(i,6) = xxx*fact;
        }
        return 0;
    }
};
const double hahn1_functor::m_x[236] = { 24.41E0 , 34.82E0 , 44.09E0 , 45.07E0 , 54.98E0 , 65.51E0 , 70.53E0 , 75.70E0 , 89.57E0 , 91.14E0 , 96.40E0 , 97.19E0 , 114.26E0 , 120.25E0 , 127.08E0 , 133.55E0 , 133.61E0 , 158.67E0 , 172.74E0 , 171.31E0 , 202.14E0 , 220.55E0 , 221.05E0 , 221.39E0 , 250.99E0 , 268.99E0 , 271.80E0 , 271.97E0 , 321.31E0 , 321.69E0 , 330.14E0 , 333.03E0 , 333.47E0 , 340.77E0 , 345.65E0 , 373.11E0 , 373.79E0 , 411.82E0 , 419.51E0 , 421.59E0 , 422.02E0 , 422.47E0 , 422.61E0 , 441.75E0 , 447.41E0 , 448.7E0  , 472.89E0 , 476.69E0 , 522.47E0 , 522.62E0 , 524.43E0 , 546.75E0 , 549.53E0 , 575.29E0 , 576.00E0 , 625.55E0 , 20.15E0 , 28.78E0 , 29.57E0 , 37.41E0 , 39.12E0 , 50.24E0 , 61.38E0 , 66.25E0 , 73.42E0 , 95.52E0 , 107.32E0 , 122.04E0 , 134.03E0 , 163.19E0 , 163.48E0 , 175.70E0 , 179.86E0 , 211.27E0 , 217.78E0 , 219.14E0 , 262.52E0 , 268.01E0 , 268.62E0 , 336.25E0 , 337.23E0 , 339.33E0 , 427.38E0 , 428.58E0 , 432.68E0 , 528.99E0 , 531.08E0 , 628.34E0 , 253.24E0 , 273.13E0 , 273.66E0 ,
282.10E0 , 346.62E0 , 347.19E0 , 348.78E0 , 351.18E0 , 450.10E0 , 450.35E0 , 451.92E0 , 455.56E0 , 552.22E0 , 553.56E0 , 555.74E0 , 652.59E0 , 656.20E0 , 14.13E0 , 20.41E0 , 31.30E0 , 33.84E0 , 39.70E0 , 48.83E0 , 54.50E0 , 60.41E0 , 72.77E0 , 75.25E0 , 86.84E0 , 94.88E0 , 96.40E0 , 117.37E0 , 139.08E0 , 147.73E0 , 158.63E0 , 161.84E0 , 192.11E0 , 206.76E0 , 209.07E0 , 213.32E0 , 226.44E0 , 237.12E0 , 330.90E0 , 358.72E0 , 370.77E0 , 372.72E0 , 396.24E0 , 416.59E0 , 484.02E0 , 495.47E0 , 514.78E0 , 515.65E0 , 519.47E0 , 544.47E0 , 560.11E0 , 620.77E0 , 18.97E0 , 28.93E0 , 33.91E0 , 40.03E0 , 44.66E0 , 49.87E0 , 55.16E0 , 60.90E0 , 72.08E0 , 85.15E0 , 97.06E0 , 119.63E0 , 133.27E0 , 143.84E0 , 161.91E0 , 180.67E0 , 198.44E0 , 226.86E0 , 229.65E0 , 258.27E0 , 273.77E0 , 339.15E0 , 350.13E0 , 362.75E0 , 371.03E0 , 393.32E0 , 448.53E0 , 473.78E0 , 511.12E0 , 524.70E0 , 548.75E0 , 551.64E0 , 574.02E0 , 623.86E0 , 21.46E0 , 24.33E0 , 33.43E0 , 39.22E0 , 44.18E0 , 55.02E0 , 94.33E0 , 96.44E0 , 118.82E0 , 128.48E0 ,
141.94E0 , 156.92E0 , 171.65E0 , 190.00E0 , 223.26E0 , 223.88E0 , 231.50E0 , 265.05E0 , 269.44E0 , 271.78E0 , 273.46E0 , 334.61E0 , 339.79E0 , 349.52E0 , 358.18E0 , 377.98E0 , 394.77E0 , 429.66E0 , 468.22E0 , 487.27E0 , 519.54E0 , 523.03E0 , 612.99E0 , 638.59E0 , 641.36E0 , 622.05E0 , 631.50E0 , 663.97E0 , 646.9E0  , 748.29E0 , 749.21E0 , 750.14E0 , 647.04E0 , 646.89E0 , 746.9E0  , 748.43E0 , 747.35E0 , 749.27E0 , 647.61E0 , 747.78E0 , 750.51E0 , 851.37E0 , 845.97E0 , 847.54E0 , 849.93E0 , 851.61E0 , 849.75E0 , 850.98E0 , 848.23E0};

// http://www.itl.nist.gov/div898/strd/nls/data/hahn1.shtml
void testNistHahn1(void)
{
  const int  n=7;
  int info;

  VectorXd x(n);

  /*
   * First try
   */
  x<< 10., -1., .05, -.00001, -.05, .001, -.000001;
  // do the computation
  hahn1_functor functor;
  LevenbergMarquardt<hahn1_functor> lm(functor);
  info = lm.minimize(x);

  // check return value
  VERIFY_IS_EQUAL(info, 1);
  VERIFY_IS_EQUAL(lm.nfev(), 11);
  VERIFY_IS_EQUAL(lm.njev(), 10);
  // check norm^2
  VERIFY_IS_APPROX(lm.fvec().squaredNorm(), 1.5324382854E+00);
  // check x
  VERIFY_IS_APPROX(x[0], 1.0776351733E+00);
  VERIFY_IS_APPROX(x[1],-1.2269296921E-01);
  VERIFY_IS_APPROX(x[2], 4.0863750610E-03);
  VERIFY_IS_APPROX(x[3],-1.426264e-06); // shoulde be : -1.4262662514E-06
  VERIFY_IS_APPROX(x[4],-5.7609940901E-03);
  VERIFY_IS_APPROX(x[5], 2.4053735503E-04);
  VERIFY_IS_APPROX(x[6],-1.2314450199E-07);

  /*
   * Second try
   */
  x<< .1, -.1, .005, -.000001, -.005, .0001, -.0000001;
  // do the computation
  info = lm.minimize(x);

  // check return value
  VERIFY_IS_EQUAL(info, 1);
  VERIFY_IS_EQUAL(lm.nfev(), 11);
  VERIFY_IS_EQUAL(lm.njev(), 10);
  // check norm^2
  VERIFY_IS_APPROX(lm.fvec().squaredNorm(), 1.5324382854E+00);
  // check x
  VERIFY_IS_APPROX(x[0], 1.077640); // should be :  1.0776351733E+00
  VERIFY_IS_APPROX(x[1], -0.1226933); // should be : -1.2269296921E-01
  VERIFY_IS_APPROX(x[2], 0.004086383); // should be : 4.0863750610E-03
  VERIFY_IS_APPROX(x[3], -1.426277e-06); // shoulde be : -1.4262662514E-06
  VERIFY_IS_APPROX(x[4],-5.7609940901E-03);
  VERIFY_IS_APPROX(x[5], 0.00024053772); // should be : 2.4053735503E-04
  VERIFY_IS_APPROX(x[6], -1.231450e-07); // should be : -1.2314450199E-07

}

struct misra1d_functor : DenseFunctor<double>
{
    misra1d_functor(void) : DenseFunctor<double>(2,14) {}
    static const double x[14];
    static const double y[14];
    int operator()(const VectorXd &b, VectorXd &fvec)
    {
        assert(b.size()==2);
        assert(fvec.size()==14);
        for(int i=0; i<14; i++) {
            fvec[i] = b[0]*b[1]*x[i]/(1.+b[1]*x[i]) - y[i];
        }
        return 0;
    }
    int df(const VectorXd &b, MatrixXd &fjac)
    {
        assert(b.size()==2);
        assert(fjac.rows()==14);
        assert(fjac.cols()==2);
        for(int i=0; i<14; i++) {
            double den = 1.+b[1]*x[i];
            fjac(i,0) = b[1]*x[i] / den;
            fjac(i,1) = b[0]*x[i]*(den-b[1]*x[i])/den/den;
        }
        return 0;
    }
};
const double misra1d_functor::x[14] = { 77.6E0, 114.9E0, 141.1E0, 190.8E0, 239.9E0, 289.0E0, 332.8E0, 378.4E0, 434.8E0, 477.3E0, 536.8E0, 593.1E0, 689.1E0, 760.0E0};
const double misra1d_functor::y[14] = { 10.07E0, 14.73E0, 17.94E0, 23.93E0, 29.61E0, 35.18E0, 40.02E0, 44.82E0, 50.76E0, 55.05E0, 61.01E0, 66.40E0, 75.47E0, 81.78E0};

// http://www.itl.nist.gov/div898/strd/nls/data/misra1d.shtml
void testNistMisra1d(void)
{
  const int n=2;
  int info;

  VectorXd x(n);

  /*
   * First try
   */
  x<< 500., 0.0001;
  // do the computation
  misra1d_functor functor;
  LevenbergMarquardt<misra1d_functor> lm(functor);
  info = lm.minimize(x);

  // check return value
  VERIFY_IS_EQUAL(info, 1);
  VERIFY_IS_EQUAL(lm.nfev(), 9);
  VERIFY_IS_EQUAL(lm.njev(), 7);
  // check norm^2
  VERIFY_IS_APPROX(lm.fvec().squaredNorm(), 5.6419295283E-02);
  // check x
  VERIFY_IS_APPROX(x[0], 4.3736970754E+02);
  VERIFY_IS_APPROX(x[1], 3.0227324449E-04);

  /*
   * Second try
   */
  x<< 450., 0.0003;
  // do the computation
  info = lm.minimize(x);

  // check return value
  VERIFY_IS_EQUAL(info, 1);
  VERIFY_IS_EQUAL(lm.nfev(), 4);
  VERIFY_IS_EQUAL(lm.njev(), 3);
  // check norm^2
  VERIFY_IS_APPROX(lm.fvec().squaredNorm(), 5.6419295283E-02);
  // check x
  VERIFY_IS_APPROX(x[0], 4.3736970754E+02);
  VERIFY_IS_APPROX(x[1], 3.0227324449E-04);
}


struct lanczos1_functor : DenseFunctor<double>
{
    lanczos1_functor(void) : DenseFunctor<double>(6,24) {}
    static const double x[24];
    static const double y[24];
    int operator()(const VectorXd &b, VectorXd &fvec)
    {
        assert(b.size()==6);
        assert(fvec.size()==24);
        for(int i=0; i<24; i++)
            fvec[i] = b[0]*exp(-b[1]*x[i]) + b[2]*exp(-b[3]*x[i]) + b[4]*exp(-b[5]*x[i])  - y[i];
        return 0;
    }
    int df(const VectorXd &b, MatrixXd &fjac)
    {
        assert(b.size()==6);
        assert(fjac.rows()==24);
        assert(fjac.cols()==6);
        for(int i=0; i<24; i++) {
            fjac(i,0) = exp(-b[1]*x[i]);
            fjac(i,1) = -b[0]*x[i]*exp(-b[1]*x[i]);
            fjac(i,2) = exp(-b[3]*x[i]);
            fjac(i,3) = -b[2]*x[i]*exp(-b[3]*x[i]);
            fjac(i,4) = exp(-b[5]*x[i]);
            fjac(i,5) = -b[4]*x[i]*exp(-b[5]*x[i]);
        }
        return 0;
    }
};
const double lanczos1_functor::x[24] = { 0.000000000000E+00, 5.000000000000E-02, 1.000000000000E-01, 1.500000000000E-01, 2.000000000000E-01, 2.500000000000E-01, 3.000000000000E-01, 3.500000000000E-01, 4.000000000000E-01, 4.500000000000E-01, 5.000000000000E-01, 5.500000000000E-01, 6.000000000000E-01, 6.500000000000E-01, 7.000000000000E-01, 7.500000000000E-01, 8.000000000000E-01, 8.500000000000E-01, 9.000000000000E-01, 9.500000000000E-01, 1.000000000000E+00, 1.050000000000E+00, 1.100000000000E+00, 1.150000000000E+00 };
const double lanczos1_functor::y[24] = { 2.513400000000E+00 ,2.044333373291E+00 ,1.668404436564E+00 ,1.366418021208E+00 ,1.123232487372E+00 ,9.268897180037E-01 ,7.679338563728E-01 ,6.388775523106E-01 ,5.337835317402E-01 ,4.479363617347E-01 ,3.775847884350E-01 ,3.197393199326E-01 ,2.720130773746E-01 ,2.324965529032E-01 ,1.996589546065E-01 ,1.722704126914E-01 ,1.493405660168E-01 ,1.300700206922E-01 ,1.138119324644E-01 ,1.000415587559E-01 ,8.833209084540E-02 ,7.833544019350E-02 ,6.976693743449E-02 ,6.239312536719E-02 };

// http://www.itl.nist.gov/div898/strd/nls/data/lanczos1.shtml
void testNistLanczos1(void)
{
  const int n=6;
  int info;

  VectorXd x(n);

  /*
   * First try
   */
  x<< 1.2, 0.3, 5.6, 5.5, 6.5, 7.6;
  // do the computation
  lanczos1_functor functor;
  LevenbergMarquardt<lanczos1_functor> lm(functor);
  info = lm.minimize(x);

  // check return value
  VERIFY_IS_EQUAL(info, 2);
  VERIFY_IS_EQUAL(lm.nfev(), 79);
  VERIFY_IS_EQUAL(lm.njev(), 72);
  // check norm^2
//   VERIFY_IS_APPROX(lm.fvec().squaredNorm(), 1.430899764097e-25);  // should be 1.4307867721E-25, but nist results are on 128-bit floats
  // check x
  VERIFY_IS_APPROX(x[0], 9.5100000027E-02);
  VERIFY_IS_APPROX(x[1], 1.0000000001E+00);
  VERIFY_IS_APPROX(x[2], 8.6070000013E-01);
  VERIFY_IS_APPROX(x[3], 3.0000000002E+00);
  VERIFY_IS_APPROX(x[4], 1.5575999998E+00);
  VERIFY_IS_APPROX(x[5], 5.0000000001E+00);

  /*
   * Second try
   */
  x<< 0.5, 0.7, 3.6, 4.2, 4., 6.3;
  // do the computation
  info = lm.minimize(x);

  // check return value
  VERIFY_IS_EQUAL(info, 2);
  VERIFY_IS_EQUAL(lm.nfev(), 9);
  VERIFY_IS_EQUAL(lm.njev(), 8);
  // check norm^2
//   VERIFY_IS_APPROX(lm.fvec().squaredNorm(), 1.428595533845e-25);  // should be 1.4307867721E-25, but nist results are on 128-bit floats
  // check x
  VERIFY_IS_APPROX(x[0], 9.5100000027E-02);
  VERIFY_IS_APPROX(x[1], 1.0000000001E+00);
  VERIFY_IS_APPROX(x[2], 8.6070000013E-01);
  VERIFY_IS_APPROX(x[3], 3.0000000002E+00);
  VERIFY_IS_APPROX(x[4], 1.5575999998E+00);
  VERIFY_IS_APPROX(x[5], 5.0000000001E+00);

}

struct rat42_functor : DenseFunctor<double>
{
    rat42_functor(void) : DenseFunctor<double>(3,9) {}
    static const double x[9];
    static const double y[9];
    int operator()(const VectorXd &b, VectorXd &fvec)
    {
        assert(b.size()==3);
        assert(fvec.size()==9);
        for(int i=0; i<9; i++) {
            fvec[i] = b[0] / (1.+exp(b[1]-b[2]*x[i])) - y[i];
        }
        return 0;
    }

    int df(const VectorXd &b, MatrixXd &fjac)
    {
        assert(b.size()==3);
        assert(fjac.rows()==9);
        assert(fjac.cols()==3);
        for(int i=0; i<9; i++) {
            double e = exp(b[1]-b[2]*x[i]);
            fjac(i,0) = 1./(1.+e);
            fjac(i,1) = -b[0]*e/(1.+e)/(1.+e);
            fjac(i,2) = +b[0]*e*x[i]/(1.+e)/(1.+e);
        }
        return 0;
    }
};
const double rat42_functor::x[9] = { 9.000E0, 14.000E0, 21.000E0, 28.000E0, 42.000E0, 57.000E0, 63.000E0, 70.000E0, 79.000E0 };
const double rat42_functor::y[9] = { 8.930E0 ,10.800E0 ,18.590E0 ,22.330E0 ,39.350E0 ,56.110E0 ,61.730E0 ,64.620E0 ,67.080E0 };

// http://www.itl.nist.gov/div898/strd/nls/data/ratkowsky2.shtml
void testNistRat42(void)
{
  const int n=3;
  int info;

  VectorXd x(n);

  /*
   * First try
   */
  x<< 100., 1., 0.1;
  // do the computation
  rat42_functor functor;
  LevenbergMarquardt<rat42_functor> lm(functor);
  info = lm.minimize(x);

  // check return value
  VERIFY_IS_EQUAL(info, 1);
  VERIFY_IS_EQUAL(lm.nfev(), 10);
  VERIFY_IS_EQUAL(lm.njev(), 8);
  // check norm^2
  VERIFY_IS_APPROX(lm.fvec().squaredNorm(), 8.0565229338E+00);
  // check x
  VERIFY_IS_APPROX(x[0], 7.2462237576E+01);
  VERIFY_IS_APPROX(x[1], 2.6180768402E+00);
  VERIFY_IS_APPROX(x[2], 6.7359200066E-02);

  /*
   * Second try
   */
  x<< 75., 2.5, 0.07;
  // do the computation
  info = lm.minimize(x);

  // check return value
  VERIFY_IS_EQUAL(info, 1);
  VERIFY_IS_EQUAL(lm.nfev(), 6);
  VERIFY_IS_EQUAL(lm.njev(), 5);
  // check norm^2
  VERIFY_IS_APPROX(lm.fvec().squaredNorm(), 8.0565229338E+00);
  // check x
  VERIFY_IS_APPROX(x[0], 7.2462237576E+01);
  VERIFY_IS_APPROX(x[1], 2.6180768402E+00);
  VERIFY_IS_APPROX(x[2], 6.7359200066E-02);
}

struct MGH10_functor : DenseFunctor<double>
{
    MGH10_functor(void) : DenseFunctor<double>(3,16) {}
    static const double x[16];
    static const double y[16];
    int operator()(const VectorXd &b, VectorXd &fvec)
    {
        assert(b.size()==3);
        assert(fvec.size()==16);
        for(int i=0; i<16; i++)
            fvec[i] =  b[0] * exp(b[1]/(x[i]+b[2])) - y[i];
        return 0;
    }
    int df(const VectorXd &b, MatrixXd &fjac)
    {
        assert(b.size()==3);
        assert(fjac.rows()==16);
        assert(fjac.cols()==3);
        for(int i=0; i<16; i++) {
            double factor = 1./(x[i]+b[2]);
            double e = exp(b[1]*factor);
            fjac(i,0) = e;
            fjac(i,1) = b[0]*factor*e;
            fjac(i,2) = -b[1]*b[0]*factor*factor*e;
        }
        return 0;
    }
};
const double MGH10_functor::x[16] = { 5.000000E+01, 5.500000E+01, 6.000000E+01, 6.500000E+01, 7.000000E+01, 7.500000E+01, 8.000000E+01, 8.500000E+01, 9.000000E+01, 9.500000E+01, 1.000000E+02, 1.050000E+02, 1.100000E+02, 1.150000E+02, 1.200000E+02, 1.250000E+02 };
const double MGH10_functor::y[16] = { 3.478000E+04, 2.861000E+04, 2.365000E+04, 1.963000E+04, 1.637000E+04, 1.372000E+04, 1.154000E+04, 9.744000E+03, 8.261000E+03, 7.030000E+03, 6.005000E+03, 5.147000E+03, 4.427000E+03, 3.820000E+03, 3.307000E+03, 2.872000E+03 };

// http://www.itl.nist.gov/div898/strd/nls/data/mgh10.shtml
void testNistMGH10(void)
{
  const int n=3;
  int info;

  VectorXd x(n);

  /*
   * First try
   */
  x<< 2., 400000., 25000.;
  // do the computation
  MGH10_functor functor;
  LevenbergMarquardt<MGH10_functor> lm(functor);
  info = lm.minimize(x);

  // check return value
  VERIFY_IS_EQUAL(info, 1); 
  VERIFY_IS_EQUAL(lm.nfev(), 284 ); 
  VERIFY_IS_EQUAL(lm.njev(), 249 ); 
  // check norm^2
  VERIFY_IS_APPROX(lm.fvec().squaredNorm(), 8.7945855171E+01);
  // check x
  VERIFY_IS_APPROX(x[0], 5.6096364710E-03);
  VERIFY_IS_APPROX(x[1], 6.1813463463E+03);
  VERIFY_IS_APPROX(x[2], 3.4522363462E+02);

  /*
   * Second try
   */
  x<< 0.02, 4000., 250.;
  // do the computation
  info = lm.minimize(x);

  // check return value
  VERIFY_IS_EQUAL(info, 1);
  VERIFY_IS_EQUAL(lm.nfev(), 126);
  VERIFY_IS_EQUAL(lm.njev(), 116);
  // check norm^2
  VERIFY_IS_APPROX(lm.fvec().squaredNorm(), 8.7945855171E+01);
  // check x
  VERIFY_IS_APPROX(x[0], 5.6096364710E-03);
  VERIFY_IS_APPROX(x[1], 6.1813463463E+03);
  VERIFY_IS_APPROX(x[2], 3.4522363462E+02);
}


struct BoxBOD_functor : DenseFunctor<double>
{
    BoxBOD_functor(void) : DenseFunctor<double>(2,6) {}
    static const double x[6];
    int operator()(const VectorXd &b, VectorXd &fvec)
    {
        static const double y[6] = { 109., 149., 149., 191., 213., 224. };
        assert(b.size()==2);
        assert(fvec.size()==6);
        for(int i=0; i<6; i++)
            fvec[i] =  b[0]*(1.-exp(-b[1]*x[i])) - y[i];
        return 0;
    }
    int df(const VectorXd &b, MatrixXd &fjac)
    {
        assert(b.size()==2);
        assert(fjac.rows()==6);
        assert(fjac.cols()==2);
        for(int i=0; i<6; i++) {
            double e = exp(-b[1]*x[i]);
            fjac(i,0) = 1.-e;
            fjac(i,1) = b[0]*x[i]*e;
        }
        return 0;
    }
};
const double BoxBOD_functor::x[6] = { 1., 2., 3., 5., 7., 10. };

// http://www.itl.nist.gov/div898/strd/nls/data/boxbod.shtml
void testNistBoxBOD(void)
{
  const int n=2;
  int info;

  VectorXd x(n);

  /*
   * First try
   */
  x<< 1., 1.;
  // do the computation
  BoxBOD_functor functor;
  LevenbergMarquardt<BoxBOD_functor> lm(functor);
  lm.setFtol(1.E6*NumTraits<double>::epsilon());
  lm.setXtol(1.E6*NumTraits<double>::epsilon());
  lm.setFactor(10);
  info = lm.minimize(x);

  // check return value
  VERIFY_IS_EQUAL(info, 1);
  VERIFY_IS_EQUAL(lm.nfev(), 31);
  VERIFY_IS_EQUAL(lm.njev(), 25);
  // check norm^2
  VERIFY_IS_APPROX(lm.fvec().squaredNorm(), 1.1680088766E+03);
  // check x
  VERIFY_IS_APPROX(x[0], 2.1380940889E+02);
  VERIFY_IS_APPROX(x[1], 5.4723748542E-01);

  /*
   * Second try
   */
  x<< 100., 0.75;
  // do the computation
  lm.resetParameters();
  lm.setFtol(NumTraits<double>::epsilon());
  lm.setXtol( NumTraits<double>::epsilon());
  info = lm.minimize(x);

  // check return value
  VERIFY_IS_EQUAL(info, 1); 
  VERIFY_IS_EQUAL(lm.nfev(), 15 ); 
  VERIFY_IS_EQUAL(lm.njev(), 14 ); 
  // check norm^2
  VERIFY_IS_APPROX(lm.fvec().squaredNorm(), 1.1680088766E+03);
  // check x
  VERIFY_IS_APPROX(x[0], 2.1380940889E+02);
  VERIFY_IS_APPROX(x[1], 5.4723748542E-01);
}

struct MGH17_functor : DenseFunctor<double>
{
    MGH17_functor(void) : DenseFunctor<double>(5,33) {}
    static const double x[33];
    static const double y[33];
    int operator()(const VectorXd &b, VectorXd &fvec)
    {
        assert(b.size()==5);
        assert(fvec.size()==33);
        for(int i=0; i<33; i++)
            fvec[i] =  b[0] + b[1]*exp(-b[3]*x[i]) +  b[2]*exp(-b[4]*x[i]) - y[i];
        return 0;
    }
    int df(const VectorXd &b, MatrixXd &fjac)
    {
        assert(b.size()==5);
        assert(fjac.rows()==33);
        assert(fjac.cols()==5);
        for(int i=0; i<33; i++) {
            fjac(i,0) = 1.;
            fjac(i,1) = exp(-b[3]*x[i]);
            fjac(i,2) = exp(-b[4]*x[i]);
            fjac(i,3) = -x[i]*b[1]*exp(-b[3]*x[i]);
            fjac(i,4) = -x[i]*b[2]*exp(-b[4]*x[i]);
        }
        return 0;
    }
};
const double MGH17_functor::x[33] = { 0.000000E+00, 1.000000E+01, 2.000000E+01, 3.000000E+01, 4.000000E+01, 5.000000E+01, 6.000000E+01, 7.000000E+01, 8.000000E+01, 9.000000E+01, 1.000000E+02, 1.100000E+02, 1.200000E+02, 1.300000E+02, 1.400000E+02, 1.500000E+02, 1.600000E+02, 1.700000E+02, 1.800000E+02, 1.900000E+02, 2.000000E+02, 2.100000E+02, 2.200000E+02, 2.300000E+02, 2.400000E+02, 2.500000E+02, 2.600000E+02, 2.700000E+02, 2.800000E+02, 2.900000E+02, 3.000000E+02, 3.100000E+02, 3.200000E+02 };
const double MGH17_functor::y[33] = { 8.440000E-01, 9.080000E-01, 9.320000E-01, 9.360000E-01, 9.250000E-01, 9.080000E-01, 8.810000E-01, 8.500000E-01, 8.180000E-01, 7.840000E-01, 7.510000E-01, 7.180000E-01, 6.850000E-01, 6.580000E-01, 6.280000E-01, 6.030000E-01, 5.800000E-01, 5.580000E-01, 5.380000E-01, 5.220000E-01, 5.060000E-01, 4.900000E-01, 4.780000E-01, 4.670000E-01, 4.570000E-01, 4.480000E-01, 4.380000E-01, 4.310000E-01, 4.240000E-01, 4.200000E-01, 4.140000E-01, 4.110000E-01, 4.060000E-01 };

// http://www.itl.nist.gov/div898/strd/nls/data/mgh17.shtml
void testNistMGH17(void)
{
  const int n=5;
  int info;

  VectorXd x(n);

  /*
   * First try
   */
  x<< 50., 150., -100., 1., 2.;
  // do the computation
  MGH17_functor functor;
  LevenbergMarquardt<MGH17_functor> lm(functor);
  lm.setFtol(NumTraits<double>::epsilon());
  lm.setXtol(NumTraits<double>::epsilon());
  lm.setMaxfev(1000);
  info = lm.minimize(x);

  // check return value
  VERIFY_IS_EQUAL(info, 2); 
//   VERIFY_IS_EQUAL(lm.nfev(), 602 ); 
  VERIFY_IS_EQUAL(lm.njev(), 545 ); 
  // check norm^2
  VERIFY_IS_APPROX(lm.fvec().squaredNorm(), 5.4648946975E-05);
  // check x
  VERIFY_IS_APPROX(x[0], 3.7541005211E-01);
  VERIFY_IS_APPROX(x[1], 1.9358469127E+00);
  VERIFY_IS_APPROX(x[2], -1.4646871366E+00);
  VERIFY_IS_APPROX(x[3], 1.2867534640E-02);
  VERIFY_IS_APPROX(x[4], 2.2122699662E-02);

  /*
   * Second try
   */
  x<< 0.5  ,1.5  ,-1   ,0.01 ,0.02;
  // do the computation
  lm.resetParameters();
  info = lm.minimize(x);

  // check return value
  VERIFY_IS_EQUAL(info, 1);
  VERIFY_IS_EQUAL(lm.nfev(), 18);
  VERIFY_IS_EQUAL(lm.njev(), 15);
  // check norm^2
  VERIFY_IS_APPROX(lm.fvec().squaredNorm(), 5.4648946975E-05);
  // check x
  VERIFY_IS_APPROX(x[0], 3.7541005211E-01);
  VERIFY_IS_APPROX(x[1], 1.9358469127E+00);
  VERIFY_IS_APPROX(x[2], -1.4646871366E+00);
  VERIFY_IS_APPROX(x[3], 1.2867534640E-02);
  VERIFY_IS_APPROX(x[4], 2.2122699662E-02);
}

struct MGH09_functor : DenseFunctor<double>
{
    MGH09_functor(void) : DenseFunctor<double>(4,11) {}
    static const double _x[11];
    static const double y[11];
    int operator()(const VectorXd &b, VectorXd &fvec)
    {
        assert(b.size()==4);
        assert(fvec.size()==11);
        for(int i=0; i<11; i++) {
            double x = _x[i], xx=x*x;
            fvec[i] = b[0]*(xx+x*b[1])/(xx+x*b[2]+b[3]) - y[i];
        }
        return 0;
    }
    int df(const VectorXd &b, MatrixXd &fjac)
    {
        assert(b.size()==4);
        assert(fjac.rows()==11);
        assert(fjac.cols()==4);
        for(int i=0; i<11; i++) {
            double x = _x[i], xx=x*x;
            double factor = 1./(xx+x*b[2]+b[3]);
            fjac(i,0) = (xx+x*b[1]) * factor;
            fjac(i,1) = b[0]*x* factor;
            fjac(i,2) = - b[0]*(xx+x*b[1]) * x * factor * factor;
            fjac(i,3) = - b[0]*(xx+x*b[1]) * factor * factor;
        }
        return 0;
    }
};
const double MGH09_functor::_x[11] = { 4., 2., 1., 5.E-1 , 2.5E-01, 1.670000E-01, 1.250000E-01,  1.E-01, 8.330000E-02, 7.140000E-02, 6.250000E-02 };
const double MGH09_functor::y[11] = { 1.957000E-01, 1.947000E-01, 1.735000E-01, 1.600000E-01, 8.440000E-02, 6.270000E-02, 4.560000E-02, 3.420000E-02, 3.230000E-02, 2.350000E-02, 2.460000E-02 };

// http://www.itl.nist.gov/div898/strd/nls/data/mgh09.shtml
void testNistMGH09(void)
{
  const int n=4;
  int info;

  VectorXd x(n);

  /*
   * First try
   */
  x<< 25., 39, 41.5, 39.;
  // do the computation
  MGH09_functor functor;
  LevenbergMarquardt<MGH09_functor> lm(functor);
  lm.setMaxfev(1000);
  info = lm.minimize(x);

  // check return value
  VERIFY_IS_EQUAL(info, 1); 
  VERIFY_IS_EQUAL(lm.nfev(), 490 ); 
  VERIFY_IS_EQUAL(lm.njev(), 376 ); 
  // check norm^2
  VERIFY_IS_APPROX(lm.fvec().squaredNorm(), 3.0750560385E-04);
  // check x
  VERIFY_IS_APPROX(x[0], 0.1928077089); // should be 1.9280693458E-01
  VERIFY_IS_APPROX(x[1], 0.19126423573); // should be 1.9128232873E-01
  VERIFY_IS_APPROX(x[2], 0.12305309914); // should be 1.2305650693E-01
  VERIFY_IS_APPROX(x[3], 0.13605395375); // should be 1.3606233068E-01

  /*
   * Second try
   */
  x<< 0.25, 0.39, 0.415, 0.39;
  // do the computation
  lm.resetParameters();
  info = lm.minimize(x);

  // check return value
  VERIFY_IS_EQUAL(info, 1);
  VERIFY_IS_EQUAL(lm.nfev(), 18);
  VERIFY_IS_EQUAL(lm.njev(), 16);
  // check norm^2
  VERIFY_IS_APPROX(lm.fvec().squaredNorm(), 3.0750560385E-04);
  // check x
  VERIFY_IS_APPROX(x[0], 0.19280781); // should be 1.9280693458E-01
  VERIFY_IS_APPROX(x[1], 0.19126265); // should be 1.9128232873E-01
  VERIFY_IS_APPROX(x[2], 0.12305280); // should be 1.2305650693E-01
  VERIFY_IS_APPROX(x[3], 0.13605322); // should be 1.3606233068E-01
}


struct Bennett5_functor : DenseFunctor<double>
{
    Bennett5_functor(void) : DenseFunctor<double>(3,154) {}
    static const double x[154];
    static const double y[154];
    int operator()(const VectorXd &b, VectorXd &fvec)
    {
        assert(b.size()==3);
        assert(fvec.size()==154);
        for(int i=0; i<154; i++)
            fvec[i] = b[0]* pow(b[1]+x[i],-1./b[2]) - y[i];
        return 0;
    }
    int df(const VectorXd &b, MatrixXd &fjac)
    {
        assert(b.size()==3);
        assert(fjac.rows()==154);
        assert(fjac.cols()==3);
        for(int i=0; i<154; i++) {
            double e = pow(b[1]+x[i],-1./b[2]);
            fjac(i,0) = e;
            fjac(i,1) = - b[0]*e/b[2]/(b[1]+x[i]);
            fjac(i,2) = b[0]*e*log(b[1]+x[i])/b[2]/b[2];
        }
        return 0;
    }
};
const double Bennett5_functor::x[154] = { 7.447168E0, 8.102586E0, 8.452547E0, 8.711278E0, 8.916774E0, 9.087155E0, 9.232590E0, 9.359535E0, 9.472166E0, 9.573384E0, 9.665293E0, 9.749461E0, 9.827092E0, 9.899128E0, 9.966321E0, 10.029280E0, 10.088510E0, 10.144430E0, 10.197380E0, 10.247670E0, 10.295560E0, 10.341250E0, 10.384950E0, 10.426820E0, 10.467000E0, 10.505640E0, 10.542830E0, 10.578690E0, 10.613310E0, 10.646780E0, 10.679150E0, 10.710520E0, 10.740920E0, 10.770440E0, 10.799100E0, 10.826970E0, 10.854080E0, 10.880470E0, 10.906190E0, 10.931260E0, 10.955720E0, 10.979590E0, 11.002910E0, 11.025700E0, 11.047980E0, 11.069770E0, 11.091100E0, 11.111980E0, 11.132440E0, 11.152480E0, 11.172130E0, 11.191410E0, 11.210310E0, 11.228870E0, 11.247090E0, 11.264980E0, 11.282560E0, 11.299840E0, 11.316820E0, 11.333520E0, 11.349940E0, 11.366100E0, 11.382000E0, 11.397660E0, 11.413070E0, 11.428240E0, 11.443200E0, 11.457930E0, 11.472440E0, 11.486750E0, 11.500860E0, 11.514770E0, 11.528490E0, 11.542020E0, 11.555380E0, 11.568550E0,
11.581560E0, 11.594420E0, 11.607121E0, 11.619640E0, 11.632000E0, 11.644210E0, 11.656280E0, 11.668200E0, 11.679980E0, 11.691620E0, 11.703130E0, 11.714510E0, 11.725760E0, 11.736880E0, 11.747890E0, 11.758780E0, 11.769550E0, 11.780200E0, 11.790730E0, 11.801160E0, 11.811480E0, 11.821700E0, 11.831810E0, 11.841820E0, 11.851730E0, 11.861550E0, 11.871270E0, 11.880890E0, 11.890420E0, 11.899870E0, 11.909220E0, 11.918490E0, 11.927680E0, 11.936780E0, 11.945790E0, 11.954730E0, 11.963590E0, 11.972370E0, 11.981070E0, 11.989700E0, 11.998260E0, 12.006740E0, 12.015150E0, 12.023490E0, 12.031760E0, 12.039970E0, 12.048100E0, 12.056170E0, 12.064180E0, 12.072120E0, 12.080010E0, 12.087820E0, 12.095580E0, 12.103280E0, 12.110920E0, 12.118500E0, 12.126030E0, 12.133500E0, 12.140910E0, 12.148270E0, 12.155570E0, 12.162830E0, 12.170030E0, 12.177170E0, 12.184270E0, 12.191320E0, 12.198320E0, 12.205270E0, 12.212170E0, 12.219030E0, 12.225840E0, 12.232600E0, 12.239320E0, 12.245990E0, 12.252620E0, 12.259200E0, 12.265750E0, 12.272240E0 };
const double Bennett5_functor::y[154] = { -34.834702E0 ,-34.393200E0 ,-34.152901E0 ,-33.979099E0 ,-33.845901E0 ,-33.732899E0 ,-33.640301E0 ,-33.559200E0 ,-33.486801E0 ,-33.423100E0 ,-33.365101E0 ,-33.313000E0 ,-33.260899E0 ,-33.217400E0 ,-33.176899E0 ,-33.139198E0 ,-33.101601E0 ,-33.066799E0 ,-33.035000E0 ,-33.003101E0 ,-32.971298E0 ,-32.942299E0 ,-32.916302E0 ,-32.890202E0 ,-32.864101E0 ,-32.841000E0 ,-32.817799E0 ,-32.797501E0 ,-32.774300E0 ,-32.757000E0 ,-32.733799E0 ,-32.716400E0 ,-32.699100E0 ,-32.678799E0 ,-32.661400E0 ,-32.644001E0 ,-32.626701E0 ,-32.612202E0 ,-32.597698E0 ,-32.583199E0 ,-32.568699E0 ,-32.554298E0 ,-32.539799E0 ,-32.525299E0 ,-32.510799E0 ,-32.499199E0 ,-32.487598E0 ,-32.473202E0 ,-32.461601E0 ,-32.435501E0 ,-32.435501E0 ,-32.426800E0 ,-32.412300E0 ,-32.400799E0 ,-32.392101E0 ,-32.380501E0 ,-32.366001E0 ,-32.357300E0 ,-32.348598E0 ,-32.339901E0 ,-32.328400E0 ,-32.319698E0 ,-32.311001E0 ,-32.299400E0 ,-32.290699E0 ,-32.282001E0 ,-32.273300E0 ,-32.264599E0 ,-32.256001E0 ,-32.247299E0
,-32.238602E0 ,-32.229900E0 ,-32.224098E0 ,-32.215401E0 ,-32.203800E0 ,-32.198002E0 ,-32.189400E0 ,-32.183601E0 ,-32.174900E0 ,-32.169102E0 ,-32.163300E0 ,-32.154598E0 ,-32.145901E0 ,-32.140099E0 ,-32.131401E0 ,-32.125599E0 ,-32.119801E0 ,-32.111198E0 ,-32.105400E0 ,-32.096699E0 ,-32.090900E0 ,-32.088001E0 ,-32.079300E0 ,-32.073502E0 ,-32.067699E0 ,-32.061901E0 ,-32.056099E0 ,-32.050301E0 ,-32.044498E0 ,-32.038799E0 ,-32.033001E0 ,-32.027199E0 ,-32.024300E0 ,-32.018501E0 ,-32.012699E0 ,-32.004002E0 ,-32.001099E0 ,-31.995300E0 ,-31.989500E0 ,-31.983700E0 ,-31.977900E0 ,-31.972099E0 ,-31.969299E0 ,-31.963501E0 ,-31.957701E0 ,-31.951900E0 ,-31.946100E0 ,-31.940300E0 ,-31.937401E0 ,-31.931601E0 ,-31.925800E0 ,-31.922899E0 ,-31.917101E0 ,-31.911301E0 ,-31.908400E0 ,-31.902599E0 ,-31.896900E0 ,-31.893999E0 ,-31.888201E0 ,-31.885300E0 ,-31.882401E0 ,-31.876600E0 ,-31.873699E0 ,-31.867901E0 ,-31.862101E0 ,-31.859200E0 ,-31.856300E0 ,-31.850500E0 ,-31.844700E0 ,-31.841801E0 ,-31.838900E0 ,-31.833099E0 ,-31.830200E0 ,
-31.827299E0 ,-31.821600E0 ,-31.818701E0 ,-31.812901E0 ,-31.809999E0 ,-31.807100E0 ,-31.801300E0 ,-31.798401E0 ,-31.795500E0 ,-31.789700E0 ,-31.786800E0 };

// http://www.itl.nist.gov/div898/strd/nls/data/bennett5.shtml
void testNistBennett5(void)
{
  const int  n=3;
  int info;

  VectorXd x(n);

  /*
   * First try
   */
  x<< -2000., 50., 0.8;
  // do the computation
  Bennett5_functor functor;
  LevenbergMarquardt<Bennett5_functor> lm(functor);
  lm.setMaxfev(1000);
  info = lm.minimize(x);

  // check return value
  VERIFY_IS_EQUAL(info, 1);
  VERIFY_IS_EQUAL(lm.nfev(), 758);
  VERIFY_IS_EQUAL(lm.njev(), 744);
  // check norm^2
  VERIFY_IS_APPROX(lm.fvec().squaredNorm(), 5.2404744073E-04);
  // check x
  VERIFY_IS_APPROX(x[0], -2.5235058043E+03);
  VERIFY_IS_APPROX(x[1], 4.6736564644E+01);
  VERIFY_IS_APPROX(x[2], 9.3218483193E-01);
  /*
   * Second try
   */
  x<< -1500., 45., 0.85;
  // do the computation
  lm.resetParameters();
  info = lm.minimize(x);

  // check return value
  VERIFY_IS_EQUAL(info, 1);
  VERIFY_IS_EQUAL(lm.nfev(), 203);
  VERIFY_IS_EQUAL(lm.njev(), 192);
  // check norm^2
  VERIFY_IS_APPROX(lm.fvec().squaredNorm(), 5.2404744073E-04);
  // check x
  VERIFY_IS_APPROX(x[0], -2523.3007865); // should be -2.5235058043E+03
  VERIFY_IS_APPROX(x[1], 46.735705771); // should be 4.6736564644E+01);
  VERIFY_IS_APPROX(x[2], 0.93219881891); // should be 9.3218483193E-01);
}

struct thurber_functor : DenseFunctor<double>
{
    thurber_functor(void) : DenseFunctor<double>(7,37) {}
    static const double _x[37];
    static const double _y[37];
    int operator()(const VectorXd &b, VectorXd &fvec)
    {
        //        int called=0; printf("call hahn1_functor with  iflag=%d, called=%d\n", iflag, called); if (iflag==1) called++;
        assert(b.size()==7);
        assert(fvec.size()==37);
        for(int i=0; i<37; i++) {
            double x=_x[i], xx=x*x, xxx=xx*x;
            fvec[i] = (b[0]+b[1]*x+b[2]*xx+b[3]*xxx) / (1.+b[4]*x+b[5]*xx+b[6]*xxx) - _y[i];
        }
        return 0;
    }
    int df(const VectorXd &b, MatrixXd &fjac)
    {
        assert(b.size()==7);
        assert(fjac.rows()==37);
        assert(fjac.cols()==7);
        for(int i=0; i<37; i++) {
            double x=_x[i], xx=x*x, xxx=xx*x;
            double fact = 1./(1.+b[4]*x+b[5]*xx+b[6]*xxx);
            fjac(i,0) = 1.*fact;
            fjac(i,1) = x*fact;
            fjac(i,2) = xx*fact;
            fjac(i,3) = xxx*fact;
            fact = - (b[0]+b[1]*x+b[2]*xx+b[3]*xxx) * fact * fact;
            fjac(i,4) = x*fact;
            fjac(i,5) = xx*fact;
            fjac(i,6) = xxx*fact;
        }
        return 0;
    }
};
const double thurber_functor::_x[37] = { -3.067E0, -2.981E0, -2.921E0, -2.912E0, -2.840E0, -2.797E0, -2.702E0, -2.699E0, -2.633E0, -2.481E0, -2.363E0, -2.322E0, -1.501E0, -1.460E0, -1.274E0, -1.212E0, -1.100E0, -1.046E0, -0.915E0, -0.714E0, -0.566E0, -0.545E0, -0.400E0, -0.309E0, -0.109E0, -0.103E0, 0.010E0, 0.119E0, 0.377E0, 0.790E0, 0.963E0, 1.006E0, 1.115E0, 1.572E0, 1.841E0, 2.047E0, 2.200E0 };
const double thurber_functor::_y[37] = { 80.574E0, 84.248E0, 87.264E0, 87.195E0, 89.076E0, 89.608E0, 89.868E0, 90.101E0, 92.405E0, 95.854E0, 100.696E0, 101.060E0, 401.672E0, 390.724E0, 567.534E0, 635.316E0, 733.054E0, 759.087E0, 894.206E0, 990.785E0, 1090.109E0, 1080.914E0, 1122.643E0, 1178.351E0, 1260.531E0, 1273.514E0, 1288.339E0, 1327.543E0, 1353.863E0, 1414.509E0, 1425.208E0, 1421.384E0, 1442.962E0, 1464.350E0, 1468.705E0, 1447.894E0, 1457.628E0};

// http://www.itl.nist.gov/div898/strd/nls/data/thurber.shtml
void testNistThurber(void)
{
  const int n=7;
  int info;

  VectorXd x(n);

  /*
   * First try
   */
  x<< 1000 ,1000 ,400 ,40 ,0.7,0.3,0.0 ;
  // do the computation
  thurber_functor functor;
  LevenbergMarquardt<thurber_functor> lm(functor);
  lm.setFtol(1.E4*NumTraits<double>::epsilon());
  lm.setXtol(1.E4*NumTraits<double>::epsilon());
  info = lm.minimize(x);

  // check return value
  VERIFY_IS_EQUAL(info, 1);
  VERIFY_IS_EQUAL(lm.nfev(), 39);
  VERIFY_IS_EQUAL(lm.njev(), 36);
  // check norm^2
  VERIFY_IS_APPROX(lm.fvec().squaredNorm(), 5.6427082397E+03);
  // check x
  VERIFY_IS_APPROX(x[0], 1.2881396800E+03);
  VERIFY_IS_APPROX(x[1], 1.4910792535E+03);
  VERIFY_IS_APPROX(x[2], 5.8323836877E+02);
  VERIFY_IS_APPROX(x[3], 7.5416644291E+01);
  VERIFY_IS_APPROX(x[4], 9.6629502864E-01);
  VERIFY_IS_APPROX(x[5], 3.9797285797E-01);
  VERIFY_IS_APPROX(x[6], 4.9727297349E-02);

  /*
   * Second try
   */
  x<< 1300 ,1500 ,500  ,75   ,1    ,0.4  ,0.05  ;
  // do the computation
  lm.resetParameters();
  lm.setFtol(1.E4*NumTraits<double>::epsilon());
  lm.setXtol(1.E4*NumTraits<double>::epsilon());
  info = lm.minimize(x);

  // check return value
  VERIFY_IS_EQUAL(info, 1);
  VERIFY_IS_EQUAL(lm.nfev(), 29);
  VERIFY_IS_EQUAL(lm.njev(), 28);
  // check norm^2
  VERIFY_IS_APPROX(lm.fvec().squaredNorm(), 5.6427082397E+03);
  // check x
  VERIFY_IS_APPROX(x[0], 1.2881396800E+03);
  VERIFY_IS_APPROX(x[1], 1.4910792535E+03);
  VERIFY_IS_APPROX(x[2], 5.8323836877E+02);
  VERIFY_IS_APPROX(x[3], 7.5416644291E+01);
  VERIFY_IS_APPROX(x[4], 9.6629502864E-01);
  VERIFY_IS_APPROX(x[5], 3.9797285797E-01);
  VERIFY_IS_APPROX(x[6], 4.9727297349E-02);
}

struct rat43_functor : DenseFunctor<double>
{
    rat43_functor(void) : DenseFunctor<double>(4,15) {}
    static const double x[15];
    static const double y[15];
    int operator()(const VectorXd &b, VectorXd &fvec)
    {
        assert(b.size()==4);
        assert(fvec.size()==15);
        for(int i=0; i<15; i++)
            fvec[i] = b[0] * pow(1.+exp(b[1]-b[2]*x[i]),-1./b[3]) - y[i];
        return 0;
    }
    int df(const VectorXd &b, MatrixXd &fjac)
    {
        assert(b.size()==4);
        assert(fjac.rows()==15);
        assert(fjac.cols()==4);
        for(int i=0; i<15; i++) {
            double e = exp(b[1]-b[2]*x[i]);
            double power = -1./b[3];
            fjac(i,0) = pow(1.+e, power);
            fjac(i,1) = power*b[0]*e*pow(1.+e, power-1.);
            fjac(i,2) = -power*b[0]*e*x[i]*pow(1.+e, power-1.);
            fjac(i,3) = b[0]*power*power*log(1.+e)*pow(1.+e, power);
        }
        return 0;
    }
};
const double rat43_functor::x[15] = { 1., 2., 3., 4., 5., 6., 7., 8., 9., 10., 11., 12., 13., 14., 15. };
const double rat43_functor::y[15] = { 16.08, 33.83, 65.80, 97.20, 191.55, 326.20, 386.87, 520.53, 590.03, 651.92, 724.93, 699.56, 689.96, 637.56, 717.41 };

// http://www.itl.nist.gov/div898/strd/nls/data/ratkowsky3.shtml
void testNistRat43(void)
{
  const int n=4;
  int info;

  VectorXd x(n);

  /*
   * First try
   */
  x<< 100., 10., 1., 1.;
  // do the computation
  rat43_functor functor;
  LevenbergMarquardt<rat43_functor> lm(functor);
  lm.setFtol(1.E6*NumTraits<double>::epsilon());
  lm.setXtol(1.E6*NumTraits<double>::epsilon());
  info = lm.minimize(x);

  // check return value
  VERIFY_IS_EQUAL(info, 1);
  VERIFY_IS_EQUAL(lm.nfev(), 27);
  VERIFY_IS_EQUAL(lm.njev(), 20);
  // check norm^2
  VERIFY_IS_APPROX(lm.fvec().squaredNorm(), 8.7864049080E+03);
  // check x
  VERIFY_IS_APPROX(x[0], 6.9964151270E+02);
  VERIFY_IS_APPROX(x[1], 5.2771253025E+00);
  VERIFY_IS_APPROX(x[2], 7.5962938329E-01);
  VERIFY_IS_APPROX(x[3], 1.2792483859E+00);

  /*
   * Second try
   */
  x<< 700., 5., 0.75, 1.3;
  // do the computation
  lm.resetParameters();
  lm.setFtol(1.E5*NumTraits<double>::epsilon());
  lm.setXtol(1.E5*NumTraits<double>::epsilon());
  info = lm.minimize(x);

  // check return value
  VERIFY_IS_EQUAL(info, 1);
  VERIFY_IS_EQUAL(lm.nfev(), 9);
  VERIFY_IS_EQUAL(lm.njev(), 8);
  // check norm^2
  VERIFY_IS_APPROX(lm.fvec().squaredNorm(), 8.7864049080E+03);
  // check x
  VERIFY_IS_APPROX(x[0], 6.9964151270E+02);
  VERIFY_IS_APPROX(x[1], 5.2771253025E+00);
  VERIFY_IS_APPROX(x[2], 7.5962938329E-01);
  VERIFY_IS_APPROX(x[3], 1.2792483859E+00);
}


struct eckerle4_functor : DenseFunctor<double>
{
    eckerle4_functor(void) : DenseFunctor<double>(3,35) {}
    static const double x[35];
    static const double y[35];
    int operator()(const VectorXd &b, VectorXd &fvec)
    {
        assert(b.size()==3);
        assert(fvec.size()==35);
        for(int i=0; i<35; i++)
            fvec[i] = b[0]/b[1] * exp(-0.5*(x[i]-b[2])*(x[i]-b[2])/(b[1]*b[1])) - y[i];
        return 0;
    }
    int df(const VectorXd &b, MatrixXd &fjac)
    {
        assert(b.size()==3);
        assert(fjac.rows()==35);
        assert(fjac.cols()==3);
        for(int i=0; i<35; i++) {
            double b12 = b[1]*b[1];
            double e = exp(-0.5*(x[i]-b[2])*(x[i]-b[2])/b12);
            fjac(i,0) = e / b[1];
            fjac(i,1) = ((x[i]-b[2])*(x[i]-b[2])/b12-1.) * b[0]*e/b12;
            fjac(i,2) = (x[i]-b[2])*e*b[0]/b[1]/b12;
        }
        return 0;
    }
};
const double eckerle4_functor::x[35] = { 400.0, 405.0, 410.0, 415.0, 420.0, 425.0, 430.0, 435.0, 436.5, 438.0, 439.5, 441.0, 442.5, 444.0, 445.5, 447.0, 448.5, 450.0, 451.5, 453.0, 454.5, 456.0, 457.5, 459.0, 460.5, 462.0, 463.5, 465.0, 470.0, 475.0, 480.0, 485.0, 490.0, 495.0, 500.0};
const double eckerle4_functor::y[35] = { 0.0001575, 0.0001699, 0.0002350, 0.0003102, 0.0004917, 0.0008710, 0.0017418, 0.0046400, 0.0065895, 0.0097302, 0.0149002, 0.0237310, 0.0401683, 0.0712559, 0.1264458, 0.2073413, 0.2902366, 0.3445623, 0.3698049, 0.3668534, 0.3106727, 0.2078154, 0.1164354, 0.0616764, 0.0337200, 0.0194023, 0.0117831, 0.0074357, 0.0022732, 0.0008800, 0.0004579, 0.0002345, 0.0001586, 0.0001143, 0.0000710 };

// http://www.itl.nist.gov/div898/strd/nls/data/eckerle4.shtml
void testNistEckerle4(void)
{
  const int n=3;
  int info;

  VectorXd x(n);

  /*
   * First try
   */
  x<< 1., 10., 500.;
  // do the computation
  eckerle4_functor functor;
  LevenbergMarquardt<eckerle4_functor> lm(functor);
  info = lm.minimize(x);

  // check return value
  VERIFY_IS_EQUAL(info, 1);
  VERIFY_IS_EQUAL(lm.nfev(), 18);
  VERIFY_IS_EQUAL(lm.njev(), 15);
  // check norm^2
  VERIFY_IS_APPROX(lm.fvec().squaredNorm(), 1.4635887487E-03);
  // check x
  VERIFY_IS_APPROX(x[0], 1.5543827178);
  VERIFY_IS_APPROX(x[1], 4.0888321754);
  VERIFY_IS_APPROX(x[2], 4.5154121844E+02);

  /*
   * Second try
   */
  x<< 1.5, 5., 450.;
  // do the computation
  info = lm.minimize(x);

  // check return value
  VERIFY_IS_EQUAL(info, 1);
  VERIFY_IS_EQUAL(lm.nfev(), 7);
  VERIFY_IS_EQUAL(lm.njev(), 6);
  // check norm^2
  VERIFY_IS_APPROX(lm.fvec().squaredNorm(), 1.4635887487E-03);
  // check x
  VERIFY_IS_APPROX(x[0], 1.5543827178);
  VERIFY_IS_APPROX(x[1], 4.0888321754);
  VERIFY_IS_APPROX(x[2], 4.5154121844E+02);
}

void test_levenberg_marquardt()
{
    // Tests using the examples provided by (c)minpack
    CALL_SUBTEST(testLmder1());
    CALL_SUBTEST(testLmder());
    CALL_SUBTEST(testLmdif1());
//     CALL_SUBTEST(testLmstr1());
//     CALL_SUBTEST(testLmstr());
    CALL_SUBTEST(testLmdif());

    // NIST tests, level of difficulty = "Lower"
    CALL_SUBTEST(testNistMisra1a());
    CALL_SUBTEST(testNistChwirut2());

    // NIST tests, level of difficulty = "Average"
    CALL_SUBTEST(testNistHahn1());
    CALL_SUBTEST(testNistMisra1d());
    CALL_SUBTEST(testNistMGH17());
    CALL_SUBTEST(testNistLanczos1());

//     // NIST tests, level of difficulty = "Higher"
    CALL_SUBTEST(testNistRat42());
    CALL_SUBTEST(testNistMGH10());
    CALL_SUBTEST(testNistBoxBOD());
//     CALL_SUBTEST(testNistMGH09());
    CALL_SUBTEST(testNistBennett5());
    CALL_SUBTEST(testNistThurber());
    CALL_SUBTEST(testNistRat43());
    CALL_SUBTEST(testNistEckerle4());
}