dft_tools/test/triqs/gfs/test_fit_tail.cpp

#//define TRIQS_ARRAYS_ENFORCE_BOUNDCHECK

#include <triqs/gfs.hpp>
#include <triqs/gfs/local/fit_tail.hpp>

using triqs::arrays::make_shape;
using namespace triqs::gfs;
using triqs::gfs::local::tail;
#define TEST(X) std::cout << BOOST_PP_STRINGIZE((X)) << " ---> "<< (X) <<std::endl<<std::endl;

int main() {

 double precision=10e-9;

 triqs::clef::placeholder<0> iom_;
 double beta =10;
 int N=100;

 auto gw = gf<imfreq>{{beta, Fermion, N}, {1, 1}};

 triqs::arrays::array<double,1> c(3);
 triqs::clef::placeholder<1> i_;

 c(i_) << (2*i_+1);

 int size=0; //means we don't know any moments
 int order_min=1; //means that the first moment in the final tail will be the first moment
 auto known_moments = tail(make_shape(1,1), size, order_min); //length is 0, first moment to fit is order_min

 gw(iom_) << c(0)/iom_ + c(1)/iom_/iom_ + c(2)/iom_/iom_/iom_; 

 //show tail
// std::cout<< "before fitting:" <<std::endl;
// for(auto &i : gw.singularity().data()) std::cout << i << std::endl;

 //erase tail
 for(auto &i : gw.singularity().data()) i = 0.0;

 size_t wn_min=50; //frequency to start the fit
 size_t wn_max=90; //final fitting frequency (included)
 int n_moments=3;  //number of moments in the final tail (including known ones)

 //restore tail
 set_tail_from_fit(gw, known_moments, n_moments, wn_min, wn_max);

// std::cout<< "after fitting:" <<std::endl; 
// for(auto &i : gw.singularity().data()) std::cout << i << std::endl;

 for(size_t i=0; i<first_dim(c); i++){
   double diff = std::abs( c(i) - gw.singularity().data()(i,0,0) );
   //std::cout<< "diff: " << diff <<std::endl;
   if (diff > precision) TRIQS_RUNTIME_ERROR<<" fit_tail error : diff="<<diff<<"\n";
 }



 //erase tail
 for(auto &i : gw.singularity().data()) i = 0.0;

 //now with a known moment
 size=1; //means that we know one moment
 order_min=1; //means that the first moment in the final tail will be the first moment
 known_moments = tail(make_shape(1,1), size, order_min); //length is 0, first moment to fit is order_min
 known_moments(1)=1.;//set the first moment
 set_tail_from_fit(gw, known_moments, n_moments, wn_min, wn_max, true);//true replace the gf data in the fitting range by the tail values


 for(size_t i=0; i<first_dim(c); i++){
   double diff = std::abs( c(i) - gw.singularity().data()(i,0,0) );
   //std::cout<< "diff: " << diff <<std::endl;
   if (diff > precision) TRIQS_RUNTIME_ERROR<<" fit_tail error : diff="<<diff<<"\n";
 }


}