Grid/lib/algorithms/approx/MultiShiftFunction.cc

    /*************************************************************************************

    Grid physics library, www.github.com/paboyle/Grid 

    Source file: ./lib/algorithms/approx/MultiShiftFunction.cc

    Copyright (C) 2015

Author: Azusa Yamaguchi <ayamaguc@staffmail.ed.ac.uk>

    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation; either version 2 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License along
    with this program; if not, write to the Free Software Foundation, Inc.,
    51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.

    See the full license in the file "LICENSE" in the top level distribution directory
    *************************************************************************************/
    /*  END LEGAL */
#include <Grid/GridCore.h>

namespace Grid {
double MultiShiftFunction::approx(double x)
{
  double a = norm;
  for(int n=0;n<poles.size();n++){
    a = a + residues[n]/(x+poles[n]);
  }
  return a;
}
void MultiShiftFunction::gnuplot(std::ostream &out)
{
  out<<"f(x) = "<<norm<<"";
  for(int n=0;n<poles.size();n++){
    out<<"+("<<residues[n]<<"/(x+"<<poles[n]<<"))";
  }
  out<<";"<<std::endl;
}
void MultiShiftFunction::csv(std::ostream &out)
{
  for (double x=lo; x<hi; x*=1.05) {
    double f = approx(x);
    double r = sqrt(x);
    out<< x<<","<<r<<","<<f<<","<<r-f<<std::endl;
  }
  return;
}
}