Esempio n. 1
0
//--------------------------------------------------------------------------------------
//
void fourier_direct  (GF_Bloc_ImTime const & Gt, GF_Bloc_ImFreq & Gw, bool time_mesh_starts_at_half_bin) { 
 double Beta = Gw.Beta;
 //assert(Gw.Statistic==Fermion); // Boson not implemented.
 check_have_same_structure (Gw,Gt,false,true);
 assert (Gw.mesh.index_min==0);

 Gw.zero();
 Array<COMPLEX,1>  G_out(Range(Gw.mesh.index_min, Gw.mesh.index_max)), 
  G_in(Range(Gt.mesh.index_min, Gt.mesh.index_max));//G_in(Gt.mesh.len());

 Gw.tail = Gt.tail;
 int N1 = Gt.N1, N2 = Gt.N2;

 double t;

 for (int n1=1; n1<=N1;n1++)
  for(int n2=1; n2<=N2;n2++)
  {
   COMPLEX d= Gw.tail[1](n1,n2), A= Gw.tail[2](n1,n2),B = Gw.tail[3](n1,n2);
   double b1, b2, b3;
   COMPLEX a1, a2, a3;
   if (Gw.Statistic == Fermion){ 
      b1 = 0; b2 =1; b3 =-1;
      a1 = d-B; a2 = (A+B)/2; a3 = (B-A)/2;
   }
   else {
      b1 = -0.5; b2 =-1; b3 =1;
      a1=4*(d-B)/3; a2=B-(d+A)/2; a3=d/6+A/2+B/3;
      }
   G_in = 0;

   for (int i =Gt.mesh.index_min; i <= Gt.mesh.index_max ; i++)
   {
    t = real(Gt.mesh[i]);
    if  (Gw.Statistic == Fermion){
    G_in(i) = Gt.data_const(n1,n2,i) - ( oneFermion(a1,b1,t,Beta) + oneFermion(a2,b2,t,Beta)+ oneFermion(a3,b3,t,Beta) );
    G_in(i) *= exp(I*Pi*t/Beta);
    }
    else {
     G_in(i) = Gt.data_const(n1,n2,i) - ( oneBoson(a1,b1,t,Beta) + oneBoson(a2,b2,t,Beta)+ oneBoson(a3,b3,t,Beta) );
    }
   }
   G_in *= Beta/Gt.numberTimeSlices;

   fourier_base(G_in, G_out, true);

   //	const COMPLEX C(I*Pi/Gt.mesh.lenTotal());
   for (int om = Gw.mesh.index_min; om<= Gw.mesh.index_max ; om++)
   {
    COMPLEX om1 = Gw.mesh[om];
    if (time_mesh_starts_at_half_bin) {
      Gw.data(n1,n2,om) = G_out(om)*exp(I*om*Pi/Gt.numberTimeSlices) + a1/(om1 - b1) + a2 / (om1-b2) + a3/(om1-b3);
    } else {
      Gw.data(n1,n2,om) = G_out(om) + a1/(om1 - b1) + a2 / (om1-b2) + a3/(om1-b3); 
    }
     

   }
  }
}
Esempio n. 2
0
void fourier_inverse (GF_Bloc_ImFreq const & Gw, GF_Bloc_ImTime & Gt, bool time_mesh_starts_at_half_bin) {

 if (abs(Gw.Beta - Gt.Beta)> 1.e-10) TRIQS_RUNTIME_ERROR<<"The time and frequency Green function are not at the same Beta";
 double Beta = Gw.Beta;
 //assert(Gw.Statistic==Fermion); // Boson not implemented.
 check_have_same_structure (Gw,Gt,false,true);
 assert (Gw.mesh.index_min==0);

 Gt.zero();
 Array<COMPLEX,1>  G_out(Range(Gt.mesh.index_min, Gt.mesh.index_max));
 Array<COMPLEX,1>  G_in(Range(Gw.mesh.index_min, Gw.mesh.index_max));

 Gt.tail = Gw.tail;
 int N1 = Gw.N1, N2 = Gw.N2;


 for (int n1=1; n1<=N1;n1++) 
  for (int n2=1; n2<=N2;n2++) 
  {
   COMPLEX d= Gt.tail[1](n1,n2), A= Gt.tail[2](n1,n2),B = Gt.tail[3](n1,n2);
   //double b1 = 0,b2 =1, b3 =-1;
   //COMPLEX a1 = d-B, a2 = (A+B)/2, a3 = (B-A)/2;
   double b1, b2, b3;
   COMPLEX a1, a2, a3;
   if (Gw.Statistic == Fermion){ 
      b1 = 0; b2 =1; b3 =-1;
      a1 = d-B; a2 = (A+B)/2; a3 = (B-A)/2;
   }
   else {
      b1 = -0.5; b2 =-1; b3 =1;
      a1=4*(d-B)/3; a2=B-(d+A)/2; a3=d/6+A/2+B/3;
      }
   G_in = 0;
   for (int i = Gw.mesh.index_min; i <= Gw.mesh.index_max ; i++) 
   {
    COMPLEX om1 = Gw.mesh[i];
    G_in(i) =  Gw.data_const(n1,n2,i) - ( a1/(om1 - b1) + a2 / (om1-b2) + a3/(om1-b3) );
    // you need an extra factor if the time mesh starts at 0.5*Beta/L
    if (time_mesh_starts_at_half_bin) G_in(i) *=  exp(-i*I*Pi/Gt.numberTimeSlices);
   }
   // for bosons GF(w=0) is divided by 2 to avoid counting it twice
   if (Gw.Statistic == Boson && !Green_Function_Are_Complex_in_time ) G_in(Gw.mesh.index_min) *= 0.5; 

   G_out = 0;
   fourier_base(G_in, G_out, false);

   // If  the Green function are NOT complex, then one use the symmetry property
   // fold the sum and get a factor 2
   double fact = (Green_Function_Are_Complex_in_time ? 1 : 2),t;
   G_out = G_out*(fact/Beta);
   for (int i =Gt.mesh.index_min; i<= Gt.mesh.index_max ; i++) 
   { 
    t= real(Gt.mesh[i]);
    if(Gw.Statistic == Fermion){
      Gt.data(n1,n2,i) = convert_green(G_out(i)*exp(-I*Pi*t/Beta) + oneFermion(a1,b1,t,Beta) + oneFermion(a2,b2,t,Beta)+ oneFermion(a3,b3,t,Beta) );}
    else {
      Gt.data(n1,n2,i) = convert_green(G_out(i) + oneBoson(a1,b1,t,Beta) + oneBoson(a2,b2,t,Beta)+ oneBoson(a3,b3,t,Beta) );}
   }
  }
}
Esempio n. 3
0
void fourier_direct(GF_Bloc_ReTime const & Gt, GF_Bloc_ReFreq & Gw)
{
  assert(Gw.Statistic==Fermion); // Boson not implemented.
  check_have_same_structure (Gw,Gt,false,true);
  assert (Gw.mesh.index_min==0);
  assert (Gt.mesh.index_min==0);
  
  const int N(Gw.mesh.len());
  const int Nt(Gt.mesh.len());
  const double omega0(2*pi/(Gt.TimeMax - Gt.TimeMin));
  const double tmin( Gt.TimeMin);
  const double Deltat((Gt.TimeMax - Gt.TimeMin));
  const double fact(Deltat/N);
  test_conformity(Gt,Gw);

  Gw.zero();

  Array<COMPLEX,1>  G_out(N),G_in(N);
  double t; COMPLEX om;

  // check the frequency grid
  for (int i = 0; i <= N/2 ; i++) {
   om = Gw.mesh[i];
   assert ( abs (om - (-N/2 + i)*omega0) < 1.e-5);
  }
  for (int i = N/2+1; i < N ; i++) {
   om = Gw.mesh[i];
   assert ( abs (om - (-N/2  + i)*omega0) < 1.e-5);
  }

  Gw.tail = Gt.tail;
  int N1 = Gw.N1, N2 = Gw.N2;

  for (int n1=1; n1<=N1;n1++)
   for (int n2=1; n2<=N2;n2++)
   {
    COMPLEX t1= Gw.tail[1](n1,n2), t2= Gw.tail[2](n1,n2); // t3 = tail[3](n1,n2);
    COMPLEX a1 = (t1 - I * t2)/2, a2 = (t1 + I * t2)/2;
    G_in = 0;
    for (int i =0; i<N ; i++) {
     t= real(Gt.mesh[i]);
     G_in(i) =  Gt.data_const(n1,n2,i) - (  a1*TH_EXPO(t,1) + a2 * TH_EXPO_NEG(t,1) );
    }

    fourier_base(G_in, G_out, true);

    for (int i = 0; i < N ; i++) {
     om = Gw.mesh[i];
     int p = (i+ N/2)%N;
     Gw.data(n1,n2,i) = G_out(p)*exp(I*om*(tmin+ fact/2))*fact + ( a1/(om + I) + a2 / (om - I)) ;
    }

   }
}
Esempio n. 4
0
void fourier_inverse (GF_Bloc_ReFreq const & Gw, GF_Bloc_ReTime & Gt ) {
 assert(Gw.Statistic==Fermion); // Boson not implemented.
 check_have_same_structure (Gw,Gt,false,true);
 assert (Gw.mesh.index_min==0);

 const int N(Gw.mesh.index_max - Gw.mesh.index_min+1);
 const int Nt(Gt.mesh.index_max - Gt.mesh.index_min+1);
 const double tmin( Gt.TimeMin);
 const double Deltat((Gt.TimeMax - Gt.TimeMin));
 const double fact(Deltat/N);
 const double pi = acos(-1);
 test_conformity(Gt,Gw);

 Gt.zero();

 Array<COMPLEX,1>  G_out(N),G_in(N);
 double t; COMPLEX om;

 Gt.tail = Gw.tail;
 int N1 = Gt.N1, N2 = Gt.N2;

 for (int n1=1; n1<=N1;n1++) 
  for (int n2=1; n2<=N2;n2++) 
  {
   COMPLEX t1= Gt.tail[1](n1,n2), t2= Gt.tail[2](n1,n2); // t3 = tail[3](n1,n2);
   COMPLEX a1 = (t1 - I * t2)/2, a2 = (t1 + I * t2)/2;
   G_in = 0;
   for (int i = 0; i < N ; i++) {
    om = Gw.mesh[i];
    int p = (i+ N/2)%N;
    G_in(p) =  Gw.data_const(n1,n2,i)/(exp(I*om*(tmin + fact/2))*fact) - ( a1/(om + I) + a2 / (om - I)) ;
   }

   fourier_base(G_in, G_out, false);

   const double corr(1.0/N);
   for (int i =0; i<N ; i++) {
    t= real(Gt.mesh[i]);
    Gt.data(n1,n2,i)  = corr*( G_out(i) + (  a1*TH_EXPO(t,1) + a2 * TH_EXPO_NEG(t,1) ) );
   }
  }
}
  void CollocationIntegratorInternal::setupFG() {

    // Interpolation order
    deg_ = getOption("interpolation_order");

    // All collocation time points
    std::vector<long double> tau_root = collocationPointsL(deg_, getOption("collocation_scheme"));

    // Coefficients of the collocation equation
    vector<vector<double> > C(deg_+1, vector<double>(deg_+1, 0));

    // Coefficients of the continuity equation
    vector<double> D(deg_+1, 0);

    // Coefficients of the quadratures
    vector<double> B(deg_+1, 0);

    // For all collocation points
    for (int j=0; j<deg_+1; ++j) {

      // Construct Lagrange polynomials to get the polynomial basis at the collocation point
      Polynomial p = 1;
      for (int r=0; r<deg_+1; ++r) {
        if (r!=j) {
          p *= Polynomial(-tau_root[r], 1)/(tau_root[j]-tau_root[r]);
        }
      }

      // Evaluate the polynomial at the final time to get the
      // coefficients of the continuity equation
      D[j] = zeroIfSmall(p(1.0L));

      // Evaluate the time derivative of the polynomial at all collocation points to
      // get the coefficients of the continuity equation
      Polynomial dp = p.derivative();
      for (int r=0; r<deg_+1; ++r) {
        C[j][r] = zeroIfSmall(dp(tau_root[r]));
      }

      // Integrate polynomial to get the coefficients of the quadratures
      Polynomial ip = p.anti_derivative();
      B[j] = zeroIfSmall(ip(1.0L));
    }

    // Symbolic inputs
    MX x0 = MX::sym("x0", f_.input(DAE_X).sparsity());
    MX p = MX::sym("p", f_.input(DAE_P).sparsity());
    MX t = MX::sym("t", f_.input(DAE_T).sparsity());

    // Implicitly defined variables (z and x)
    MX v = MX::sym("v", deg_*(nx_+nz_));
    vector<int> v_offset(1, 0);
    for (int d=0; d<deg_; ++d) {
      v_offset.push_back(v_offset.back()+nx_);
      v_offset.push_back(v_offset.back()+nz_);
    }
    vector<MX> vv = vertsplit(v, v_offset);
    vector<MX>::const_iterator vv_it = vv.begin();

    // Collocated states
    vector<MX> x(deg_+1), z(deg_+1);
    for (int d=1; d<=deg_; ++d) {
      x[d] = reshape(*vv_it++, this->x0().shape());
      z[d] = reshape(*vv_it++, this->z0().shape());
    }
    casadi_assert(vv_it==vv.end());

    // Collocation time points
    vector<MX> tt(deg_+1);
    for (int d=0; d<=deg_; ++d) {
      tt[d] = t + h_*tau_root[d];
    }

    // Equations that implicitly define v
    vector<MX> eq;

    // Quadratures
    MX qf = MX::zeros(f_.output(DAE_QUAD).sparsity());

    // End state
    MX xf = D[0]*x0;

    // For all collocation points
    for (int j=1; j<deg_+1; ++j) {
      //for (int j=deg_; j>=1; --j) {

      // Evaluate the DAE
      vector<MX> f_arg(DAE_NUM_IN);
      f_arg[DAE_T] = tt[j];
      f_arg[DAE_P] = p;
      f_arg[DAE_X] = x[j];
      f_arg[DAE_Z] = z[j];
      vector<MX> f_res = f_.call(f_arg);

      // Get an expression for the state derivative at the collocation point
      MX xp_j = C[0][j] * x0;
      for (int r=1; r<deg_+1; ++r) {
        xp_j += C[r][j] * x[r];
      }

      // Add collocation equation
      eq.push_back(vec(h_*f_res[DAE_ODE] - xp_j));

      // Add the algebraic conditions
      eq.push_back(vec(f_res[DAE_ALG]));

      // Add contribution to the final state
      xf += D[j]*x[j];

      // Add contribution to quadratures
      qf += (B[j]*h_)*f_res[DAE_QUAD];
    }

    // Form forward discrete time dynamics
    vector<MX> F_in(DAE_NUM_IN);
    F_in[DAE_T] = t;
    F_in[DAE_X] = x0;
    F_in[DAE_P] = p;
    F_in[DAE_Z] = v;
    vector<MX> F_out(DAE_NUM_OUT);
    F_out[DAE_ODE] = xf;
    F_out[DAE_ALG] = vertcat(eq);
    F_out[DAE_QUAD] = qf;
    F_ = MXFunction(F_in, F_out);
    F_.init();

    // Backwards dynamics
    // NOTE: The following is derived so that it will give the exact adjoint
    // sensitivities whenever g is the reverse mode derivative of f.
    if (!g_.isNull()) {

      // Symbolic inputs
      MX rx0 = MX::sym("x0", g_.input(RDAE_RX).sparsity());
      MX rp = MX::sym("p", g_.input(RDAE_RP).sparsity());

      // Implicitly defined variables (rz and rx)
      MX rv = MX::sym("v", deg_*(nrx_+nrz_));
      vector<int> rv_offset(1, 0);
      for (int d=0; d<deg_; ++d) {
        rv_offset.push_back(rv_offset.back()+nrx_);
        rv_offset.push_back(rv_offset.back()+nrz_);
      }
      vector<MX> rvv = vertsplit(rv, rv_offset);
      vector<MX>::const_iterator rvv_it = rvv.begin();

      // Collocated states
      vector<MX> rx(deg_+1), rz(deg_+1);
      for (int d=1; d<=deg_; ++d) {
        rx[d] = reshape(*rvv_it++, this->rx0().shape());
        rz[d] = reshape(*rvv_it++, this->rz0().shape());
      }
      casadi_assert(rvv_it==rvv.end());

      // Equations that implicitly define v
      eq.clear();

      // Quadratures
      MX rqf = MX::zeros(g_.output(RDAE_QUAD).sparsity());

      // End state
      MX rxf = D[0]*rx0;

      // For all collocation points
      for (int j=1; j<deg_+1; ++j) {

        // Evaluate the backward DAE
        vector<MX> g_arg(RDAE_NUM_IN);
        g_arg[RDAE_T] = tt[j];
        g_arg[RDAE_P] = p;
        g_arg[RDAE_X] = x[j];
        g_arg[RDAE_Z] = z[j];
        g_arg[RDAE_RX] = rx[j];
        g_arg[RDAE_RZ] = rz[j];
        g_arg[RDAE_RP] = rp;
        vector<MX> g_res = g_.call(g_arg);

        // Get an expression for the state derivative at the collocation point
        MX rxp_j = -D[j]*rx0;
        for (int r=1; r<deg_+1; ++r) {
          rxp_j += (B[r]*C[j][r]) * rx[r];
        }

        // Add collocation equation
        eq.push_back(vec(h_*B[j]*g_res[RDAE_ODE] - rxp_j));

        // Add the algebraic conditions
        eq.push_back(vec(g_res[RDAE_ALG]));

        // Add contribution to the final state
        rxf += -B[j]*C[0][j]*rx[j];

        // Add contribution to quadratures
        rqf += h_*B[j]*g_res[RDAE_QUAD];
      }

      // Form backward discrete time dynamics
      vector<MX> G_in(RDAE_NUM_IN);
      G_in[RDAE_T] = t;
      G_in[RDAE_X] = x0;
      G_in[RDAE_P] = p;
      G_in[RDAE_Z] = v;
      G_in[RDAE_RX] = rx0;
      G_in[RDAE_RP] = rp;
      G_in[RDAE_RZ] = rv;
      vector<MX> G_out(RDAE_NUM_OUT);
      G_out[RDAE_ODE] = rxf;
      G_out[RDAE_ALG] = vertcat(eq);
      G_out[RDAE_QUAD] = rqf;
      G_ = MXFunction(G_in, G_out);
      G_.init();
    }
  }
Esempio n. 6
0
void LiftedSQPInternal::init(){
  // Call the init method of the base class
  NlpSolverInternal::init();

  // Number of lifted variables
  nv = getOption("num_lifted");
  if(verbose_){
    cout << "Initializing SQP method with " << nx_ << " variables and " << ng_ << " constraints." << endl;
    cout << "Lifting " << nv << " variables." << endl;
    if(gauss_newton_){
      cout << "Gauss-Newton objective with " << F_.input().numel() << " terms." << endl;
    }
  }
  
  // Read options
  max_iter_ = getOption("max_iter");
  max_iter_ls_ = getOption("max_iter_ls");
  toldx_ = getOption("toldx");
  tolgl_ = getOption("tolgl");
  sigma_ = getOption("sigma");
  rho_ = getOption("rho");
  mu_safety_ = getOption("mu_safety");
  eta_ = getOption("eta");
  tau_ = getOption("tau");
    
  // Assume SXFunction for now
  SXFunction ffcn = shared_cast<SXFunction>(F_);
  casadi_assert(!ffcn.isNull());
  SXFunction gfcn = shared_cast<SXFunction>(G_);
  casadi_assert(!gfcn.isNull());
  
  // Extract the free variables and split into independent and dependent variables
  SX x = ffcn.inputExpr(0);
  int nx = x.size();
  nu = nx-nv;
  SX u = x[Slice(0,nu)];
  SX v = x[Slice(nu,nu+nv)];

  // Extract the constraint equations and split into constraints and definitions of dependent variables
  SX f1 = ffcn.outputExpr(0);
  int nf1 = f1.numel();
  SX g = gfcn.outputExpr(0);
  int nf2 = g.numel()-nv;
  SX v_eq = g(Slice(0,nv));
  SX f2 = g(Slice(nv,nv+nf2));
  
  // Definition of v
  SX v_def = v_eq + v;

  // Objective function
  SX f;
  
  // Multipliers
  SX lam_x, lam_g, lam_f2;
  if(gauss_newton_){
    
    // Least square objective
    f = inner_prod(f1,f1)/2;
    
  } else {
    
    // Scalar objective function
    f = f1;
    
    // Lagrange multipliers for the simple bounds on u
    SX lam_u = ssym("lam_u",nu);
    
    // Lagrange multipliers for the simple bounds on v
    SX lam_v = ssym("lam_v",nv);
    
    // Lagrange multipliers for the simple bounds on x
    lam_x = vertcat(lam_u,lam_v);

    // Lagrange multipliers corresponding to the definition of the dependent variables
    SX lam_v_eq = ssym("lam_v_eq",nv);

    // Lagrange multipliers for the nonlinear constraints that aren't eliminated
    lam_f2 = ssym("lam_f2",nf2);

    if(verbose_){
      cout << "Allocated intermediate variables." << endl;
    }
    
    // Lagrange multipliers for constraints
    lam_g = vertcat(lam_v_eq,lam_f2);
    
    // Lagrangian function
    SX lag = f + inner_prod(lam_x,x);
    if(!f2.empty()) lag += inner_prod(lam_f2,f2);
    if(!v.empty()) lag += inner_prod(lam_v_eq,v_def);
    
    // Gradient of the Lagrangian
    SX lgrad = casadi::gradient(lag,x);
    if(!v.empty()) lgrad -= vertcat(SX::zeros(nu),lam_v_eq); // Put here to ensure that lgrad is of the form "h_extended -v_extended"
    makeDense(lgrad);
    if(verbose_){
      cout << "Generated the gradient of the Lagrangian." << endl;
    }

    // Condensed gradient of the Lagrangian
    f1 = lgrad[Slice(0,nu)];
    nf1 = nu;
    
    // Gradient of h
    SX v_eq_grad = lgrad[Slice(nu,nu+nv)];
    
    // Reverse lam_v_eq and v_eq_grad
    SX v_eq_grad_reversed = v_eq_grad;
    copy(v_eq_grad.rbegin(),v_eq_grad.rend(),v_eq_grad_reversed.begin());
    SX lam_v_eq_reversed = lam_v_eq;
    copy(lam_v_eq.rbegin(),lam_v_eq.rend(),lam_v_eq_reversed.begin());
    
    // Augment h and lam_v_eq
    v_eq.append(v_eq_grad_reversed);
    v.append(lam_v_eq_reversed);
  }

  // Residual function G
  SXVector G_in(G_NUM_IN);
  G_in[G_X] = x;
  G_in[G_LAM_X] = lam_x;
  G_in[G_LAM_G] = lam_g;

  SXVector G_out(G_NUM_OUT);
  G_out[G_D] = v_eq;
  G_out[G_G] = g;
  G_out[G_F] = f;

  rfcn_ = SXFunction(G_in,G_out);
  rfcn_.setOption("number_of_fwd_dir",0);
  rfcn_.setOption("number_of_adj_dir",0);
  rfcn_.setOption("live_variables",true);
  rfcn_.init();
  if(verbose_){
    cout << "Generated residual function ( " << shared_cast<SXFunction>(rfcn_).getAlgorithmSize() << " nodes)." << endl;
  }
  
  // Difference vector d
  SX d = ssym("d",nv);
  if(!gauss_newton_){
    vector<SX> dg = ssym("dg",nv).data();
    reverse(dg.begin(),dg.end());
    d.append(dg);
  }

  // Substitute out the v from the h
  SX d_def = (v_eq + v)-d;
  SXVector ex(3);
  ex[0] = f1;
  ex[1] = f2;
  ex[2] = f;
  substituteInPlace(v, d_def, ex, false);
  SX f1_z = ex[0];
  SX f2_z = ex[1];
  SX f_z = ex[2];
  
  // Modified function Z
  enum ZIn{Z_U,Z_D,Z_LAM_X,Z_LAM_F2,Z_NUM_IN};
  SXVector zfcn_in(Z_NUM_IN);
  zfcn_in[Z_U] = u;
  zfcn_in[Z_D] = d;
  zfcn_in[Z_LAM_X] = lam_x;
  zfcn_in[Z_LAM_F2] = lam_f2;
  
  enum ZOut{Z_D_DEF,Z_F12,Z_NUM_OUT};
  SXVector zfcn_out(Z_NUM_OUT);
  zfcn_out[Z_D_DEF] = d_def;
  zfcn_out[Z_F12] = vertcat(f1_z,f2_z);
  
  SXFunction zfcn(zfcn_in,zfcn_out);
  zfcn.init();
  if(verbose_){
    cout << "Generated reconstruction function ( " << zfcn.getAlgorithmSize() << " nodes)." << endl;
  }

  // Matrix A and B in lifted Newton
  SX B = zfcn.jac(Z_U,Z_F12);
  SX B1 = B(Slice(0,nf1),Slice(0,B.size2()));
  SX B2 = B(Slice(nf1,B.size1()),Slice(0,B.size2()));
  if(verbose_){
    cout << "Formed B1 (dimension " << B1.size1() << "-by-" << B1.size2() << ", "<< B1.size() << " nonzeros) " <<
    "and B2 (dimension " << B2.size1() << "-by-" << B2.size2() << ", "<< B2.size() << " nonzeros)." << endl;
  }
  
  // Step in u
  SX du = ssym("du",nu);
  SX dlam_f2 = ssym("dlam_f2",lam_f2.sparsity());
  
  SX b1 = f1_z;
  SX b2 = f2_z;
  SX e;
  if(nv > 0){
    
    // Directional derivative of Z
    vector<vector<SX> > Z_fwdSeed(2,zfcn_in);
    vector<vector<SX> > Z_fwdSens(2,zfcn_out);
    vector<vector<SX> > Z_adjSeed;
    vector<vector<SX> > Z_adjSens;
    
    Z_fwdSeed[0][Z_U].setZero();
    Z_fwdSeed[0][Z_D] = -d;
    Z_fwdSeed[0][Z_LAM_X].setZero();
    Z_fwdSeed[0][Z_LAM_F2].setZero();
    
    Z_fwdSeed[1][Z_U] = du;
    Z_fwdSeed[1][Z_D] = -d;
    Z_fwdSeed[1][Z_LAM_X].setZero();
    Z_fwdSeed[1][Z_LAM_F2] = dlam_f2;
    
    zfcn.eval(zfcn_in,zfcn_out,Z_fwdSeed,Z_fwdSens,Z_adjSeed,Z_adjSens);
    
    b1 += Z_fwdSens[0][Z_F12](Slice(0,nf1));
    b2 += Z_fwdSens[0][Z_F12](Slice(nf1,B.size1()));
    e = Z_fwdSens[1][Z_D_DEF];
  }
  if(verbose_){
    cout << "Formed b1 (dimension " << b1.size1() << "-by-" << b1.size2() << ", "<< b1.size() << " nonzeros) " <<
    "and b2 (dimension " << b2.size1() << "-by-" << b2.size2() << ", "<< b2.size() << " nonzeros)." << endl;
  }
  
  // Generate Gauss-Newton Hessian
  if(gauss_newton_){
    b1 = mul(trans(B1),b1);
    B1 = mul(trans(B1),B1);
    if(verbose_){
      cout << "Gauss Newton Hessian (dimension " << B1.size1() << "-by-" << B1.size2() << ", "<< B1.size() << " nonzeros)." << endl;
    }
  }
  
  // Make sure b1 and b2 are dense vectors
  makeDense(b1);
  makeDense(b2);
  
  // Quadratic approximation
  SXVector lfcn_in(LIN_NUM_IN);
  lfcn_in[LIN_X] = x;
  lfcn_in[LIN_D] = d;
  lfcn_in[LIN_LAM_X] = lam_x;
  lfcn_in[LIN_LAM_G] = lam_g;
  
  SXVector lfcn_out(LIN_NUM_OUT);
  lfcn_out[LIN_F1] = b1;
  lfcn_out[LIN_J1] = B1;
  lfcn_out[LIN_F2] = b2;
  lfcn_out[LIN_J2] = B2;
  lfcn_ = SXFunction(lfcn_in,lfcn_out);
//   lfcn_.setOption("verbose",true);
  lfcn_.setOption("number_of_fwd_dir",0);
  lfcn_.setOption("number_of_adj_dir",0);
  lfcn_.setOption("live_variables",true);
  lfcn_.init();
  if(verbose_){
    cout << "Generated linearization function ( " << shared_cast<SXFunction>(lfcn_).getAlgorithmSize() << " nodes)." << endl;
  }
    
  // Step expansion
  SXVector efcn_in(EXP_NUM_IN);
  copy(lfcn_in.begin(),lfcn_in.end(),efcn_in.begin());
  efcn_in[EXP_DU] = du;
  efcn_in[EXP_DLAM_F2] = dlam_f2;
  efcn_ = SXFunction(efcn_in,e);
  efcn_.setOption("number_of_fwd_dir",0);
  efcn_.setOption("number_of_adj_dir",0);
  efcn_.setOption("live_variables",true);
  efcn_.init();
  if(verbose_){
    cout << "Generated step expansion function ( " << shared_cast<SXFunction>(efcn_).getAlgorithmSize() << " nodes)." << endl;
  }
  
  // Current guess for the primal solution
  DMatrix &x_k = output(NLP_SOLVER_X);
  
  // Current guess for the dual solution
  DMatrix &lam_x_k = output(NLP_SOLVER_LAM_X);
  DMatrix &lam_g_k = output(NLP_SOLVER_LAM_G);

  // Allocate a QP solver
  QpSolverCreator qp_solver_creator = getOption("qp_solver");
  qp_solver_ = qp_solver_creator(B1.sparsity(),B2.sparsity());
  
  // Set options if provided
  if(hasSetOption("qp_solver_options")){
    Dictionary qp_solver_options = getOption("qp_solver_options");
    qp_solver_.setOption(qp_solver_options);
  }
  
  // Initialize the QP solver
  qp_solver_.init();
  if(verbose_){
    cout << "Allocated QP solver." << endl;
  }

  // Residual
  d_k_ = DMatrix(d.sparsity(),0);
  
  // Primal step
  dx_k_ = DMatrix(x_k.sparsity());

  // Dual step
  dlam_x_k_ = DMatrix(lam_x_k.sparsity());
  dlam_g_k_ = DMatrix(lam_g_k.sparsity());
  
}