ABACUS/src/EXECS/LiebLin_Fourier_to_x_t_from...

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

This software is part of J.-S. Caux's ABACUS library.

Copyright (c) J.-S. Caux.

-----------------------------------------------------------

File:  LiebLin_Fourier_to_x_t.cc

Purpose:  Fourier transform to spacetime correlator for LiebLin.

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

#include "ABACUS.h"

using namespace std;
using namespace ABACUS;


int main(int argc, char* argv[])
{
  if (argc != 11) { // provide some info

    cout << endl << "Welcome to ABACUS\t(copyright J.-S. Caux)." << endl;
    cout << endl << "Usage of LiebLin_Fourier_to_x_equal_t executable: " << endl;
    cout << endl << "Provide the following arguments:" << endl << endl;
    cout << "char whichDSF \t\t Which structure factor ?  Options are:  "
      "d for rho rho, g for psi psi{dagger}, o for psi{dagger} psi" << endl;
    cout << "DP c_int \t\t Value of the interaction parameter" << endl;
    cout << "DP L \t\t\t Length of the system" << endl;
    cout << "int N \t\t\t Number of particles" << endl;
    cout << "int iKmin" << endl << "int iKmax \t\t Min and max momentum integers scanned over" << endl;
    cout << "RAW file name" << endl;
    cout << "int Npts_x Number of points in space for the Fourier transform" << endl;
    cout << "int Npts_t \t Number of points in time for the Fourier transform" << endl;
    cout << "DP t_max \t Max time to be used" << endl;
  }

  else { // (argc == 9), correct nr of arguments
    char whichDSF = *argv[1];
    DP c_int = atof(argv[2]);
    DP L = atof(argv[3]);
    int N = atoi(argv[4]);
    int iKmin = atoi(argv[5]);
    int iKmax = atoi(argv[6]);
    char* rawfilename = argv[7];
    int Npts_x = atoi(argv[8]);
    int Npts_t = atoi(argv[9]);
    DP t_max = atof(argv[10]);

    ifstream RAW_infile;
    RAW_infile.open(rawfilename);
    if (RAW_infile.fail()) {
      cout << rawfilename << endl;
      ABACUSerror("Could not open RAW_infile... ");
    }

    // Define the output file name: use the RAW file name but with different suffix

    stringstream SFT_stringstream;    string SFT_string;
    SFT_stringstream << rawfilename << "_xtf_Nx_" << Npts_x << "_Nt_" << Npts_t << "_tmax_" << t_max;
    SFT_string = SFT_stringstream.str();    const char* SFT_Cstr = SFT_string.c_str();
    ofstream SFT_outfile;
    SFT_outfile.open(SFT_Cstr);
    if (SFT_outfile.fail()) ABACUSerror("Could not open SFT_outfile... ");

    DP omega;
    int iK;
    DP FF;
    DP dev;
    string label;

    // Define space coordinates: between 0 and L
    Vect_DP xlattice(Npts_x);
    for (int i = 0; i < Npts_x; ++i) xlattice[i] = i * L/Npts_x;

    // Now define time coordinates: between 0 and t_max
    Vect_DP tlattice(Npts_t);
    for (int i = 0; i < Npts_t; ++i) tlattice[i] = i * t_max/Npts_t;

    RecMat<complex<DP> > FT(0.0, Npts_x, Npts_t);
    DP twopioverL = twoPI/L;
    DP FFsq;
    complex<DP> exp_ik, exp_miomega;
    while (RAW_infile.peek() != EOF) {
      RAW_infile >> omega >> iK >> FF >> dev >> label;
      FFsq = FF * FF;
      exp_ik = exp(II * (iK * twopioverL));
      exp_miomega = exp(-II * omega);
      for (int ix = 0; ix < Npts_x; ++ix)
	for (int it = 0; it < Npts_t; ++it)
	  //FT[ix][it] += FF * FF * exp(II * (iK * twopioverL * xlattice[ix] - omega * tlattice[it]));
	  FT[ix][it] = FFsq * pow(exp_ik, xlattice[ix]) * pow(exp_miomega, tlattice[it]);
    }
    RAW_infile.close();

    // Reset proper normalization:
    // for (int ix = 0; ix < Npts_x; ++ix)
    //   for (int it = 0; it < Npts_t; ++it)
    // 	FT[ix][it] *= twopioverL;

    // Output to file:
    for (int ix = 0; ix < Npts_x; ++ix) {
      if (ix > 0) SFT_outfile << endl;
      for (int it = 0; it < Npts_t; ++it)
	SFT_outfile << FT[ix][it] << "\t";
    }

    SFT_outfile.close();
  }

  return(0);

}