df1b2imp.cpp

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/*
 * $Id$
 *
 * Author: David Fournier
 * Copyright (c) 2008-2012 Regents of the University of California
 */
#  include <admodel.h>
#  include <df1b2fun.h>
#  include <adrndeff.h>

double calculate_importance_sample(const dvector& x,const dvector& u0,
  const dmatrix& Hess,const dvector& _xadjoint,const dvector& _uadjoint,
  const dmatrix& _Hessadjoint,function_minimizer * pmin)
{
  ADUNCONST(dvector,xadjoint)
  ADUNCONST(dvector,uadjoint)
  ADUNCONST(dmatrix,Hessadjoint)
  const int xs=x.size();
  const int us=u0.size();
  gradient_structure::set_YES_DERIVATIVES();
  int nvar=x.size()+u0.size()+u0.size()*u0.size();
  independent_variables y(1,nvar);

  // need to set random effects active together with whatever
  // init parameters should be active in this phase
  initial_params::set_inactive_only_random_effects();
  initial_params::set_active_random_effects();
  /*int onvar=*/initial_params::nvarcalc();
  initial_params::xinit(y);    // get the initial values into the
  // do we need this next line?
  y(1,xs)=x;

  int i,j;
  dvar_vector d(1,xs+us);

  // contribution for quadratic prior
  if (quadratic_prior::get_num_quadratic_prior()>0)
  {
    //Hess+=quadratic_prior::get_cHessian_contribution();
    int & vxs = (int&)(xs);
    quadratic_prior::get_cHessian_contribution(Hess,vxs);
  }
 // Here need hooks for sparse matrix structures
  int ii=xs+us+1;
  for (i=1;i<=us;i++)
    for (j=1;j<=us;j++)
    y(ii++)=Hess(i,j);

  dvar_vector vy=dvar_vector(y);
  initial_params::stddev_vscale(d,vy);
  dvar_matrix vHess(1,us,1,us);
  ii=xs+us+1;
  if (initial_df1b2params::have_bounded_random_effects)
  {
    cerr << "can't do importance sampling with bounded random effects"
     " at present" << endl;
    ad_exit(1);
  }
  else
  {
    for (i=1;i<=us;i++)
    {
      for (j=1;j<=us;j++)
      {
        vHess(i,j)=vy(ii++);
      }
    }
  }

   int nsamp=pmin->lapprox->num_importance_samples;
   dvar_vector sample_value(1,nsamp);
   sample_value.initialize();
   dvar_matrix ch=choleski_decomp(inv(vHess));

   dvariable vf=0.0;
   for (int is=1;is<=nsamp;is++)
   {
     dvar_vector tau=ch*pmin->lapprox->epsilon(is);

     vy(xs+1,xs+us).shift(1)+=tau;
     initial_params::reset(vy);    // get the values into the model
     vy(xs+1,xs+us).shift(1)-=tau;

     *objective_function_value::pobjfun=0.0;
     pmin->AD_uf_outer();

     sample_value(is)=*objective_function_value::pobjfun
       -0.5*norm2(pmin->lapprox->epsilon(is));
   }


   if (laplace_approximation_calculator::
     print_importance_sampling_weights_flag==1)
   {
     double min_vf=min(value(sample_value));
     dvector tmp=exp(value(sample_value)-min_vf);
     cout << "The unsorted normalized importance samplng weights are " << endl
          << tmp << endl;
     cout << "The sorted normalized importance samplng weights are " << endl
          << sort(tmp) << endl;
     ad_exit(1);
   }


   dvariable min_vf=min(sample_value);
   vf=min_vf-log(mean(exp(min_vf-sample_value)));
   vf-=us*0.91893853320467241;

   int sgn=0;
   dvariable ld;
   if (ad_comm::no_ln_det_choleski_flag)
     ld=0.5*ln_det(vHess,sgn);
   else
     ld=0.5*ln_det_choleski(vHess);

   vf+=ld;
   double f=value(vf);
   dvector g(1,nvar);
   gradcalc(nvar,g);

   // put uhat back into the model
   gradient_structure::set_NO_DERIVATIVES();
   vy(xs+1,xs+us).shift(1)=u0;
   initial_params::reset(vy);    // get the values into the model
   gradient_structure::set_YES_DERIVATIVES();

  ii=1;
  for (i=1;i<=xs;i++)
    xadjoint(i)=g(ii++);
  for (i=1;i<=us;i++)
    uadjoint(i)=g(ii++);
  for (i=1;i<=us;i++)
    for (j=1;j<=us;j++)
      Hessadjoint(i,j)=g(ii++);
  return f;
}