ABACUS/src/UTILS/Smoothen_RAW_into_SF_LiebLin_Scaled.cc

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

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

Copyright (c) J.-S. Caux.

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

File:  Smoothen_RAW_into_SF_LiebLin_Scaled.cc

Purpose:  from a .raw file, produces .dsf (dynamical sf) file
          with gaussian width a function of momentum, and a .ssf (static sf) file.

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

#include "ABACUS.h"

using namespace std;
using namespace ABACUS;

namespace ABACUS {

  DP Smoothen_RAW_into_SF_LiebLin_Scaled (string prefix, DP L, int N, int iKmin, int iKmax, int DiK,
					  DP ommin, DP ommax, int Nom, DP width, DP normalization)
  {
    // DiK is the (half-)window in iK which is averaged over. A single iK means DiK == 0.

    // ommax is omega max for .dsf file, Nom is the number of omega slots used.

    // width is measured in units of the level spacing (for each momentum independently).

    // gwidth is the width of the smoothing Gaussian, defined as
    // exp(-omega^2/(2 * gwidth^2))

    // Open the original raw file:
    stringstream RAW_stringstream;    string RAW_string;
    RAW_stringstream << prefix << ".raw";
    RAW_string = RAW_stringstream.str();    const char* RAW_Cstr = RAW_string.c_str();

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

    if (iKmax - iKmin + 1 < 0) ABACUSerror("Improper iKmin, iKmax in Smoothen_RAW_into_SF_LiebLin_Scaled");
    RecMat<DP> DSFS(Nom, iKmax - iKmin + 1);
    Vect_DP SSF(0.0, iKmax - iKmin + 1);

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

    // Momenta: average over 2*DiK + 1 entries. Weigh them linearly decreasing away from central one.
    // Setting central one to value 1 + DiK,
    // total weight is 1 + DiK + 2* \sum_1^DiK n = 1 + DiK + DiK (DiK + 1) = (DiK + 1)^2.
    // Weight given is thus abs(DiK + 1 - (iK - iK'))/(DiK + 1)^2 for abs(iK - iK') <= DiK.
    Vect_DP Kweight(DiK + 1);
    for (int i = 0; i < DiK + 1; ++i) Kweight[i] = (DiK + 1.0 - i)/pow(DiK + 1.0, 2);

    Vect_DP omegaout (Nom);
    for (int i = 0; i < Nom; ++i) omegaout[i] = ommin + (0.5 + i) * (ommax - ommin)/Nom;

    DP d_omega;
    Vect_DP gwidth (iKmax - iKmin + 1);

    // At fixed momentum k, we take the bandwidth as bw = e_1 (k) - e_2 (k) calculated in TG limit,
    // i.e. bw = k^2 + 2\pi \rho k - (-k^2 + 2\pi\rho k) = 2 k^2 for 0 < k < 2k_F = 2\pi \rho
    // and  bw = 2 * (2\pi \rho)^2 for 2k_F < k.

    // For iK <= N, there are iK states in bw.
    // For iK > N, there are N states.

    for (iK = iKmin; iK <= iKmax; ++iK)
      // Make sure the width does not become lower than the omegaout raster:
      gwidth[iK - iKmin] = ABACUS::max(2.0 * (ommax - ommin)/Nom, width * 2.0
				       * ABACUS::min( pow(twoPI * ABACUS::max(abs(iK),1)/L, 2.0),
						      pow(twoPI * N/L, 2.0))/ABACUS::min(N, ABACUS::max(abs(iK), 1)));


    Vect_DP big_gwidth_used (iKmax - iKmin + 1);
    for (iK = iKmin; iK <= iKmax; ++iK)
      big_gwidth_used[iK - iKmin] = 10.0 * gwidth[iK - iKmin];  // neglect terms having gaussian < exp(-50)
    Vect_DP oneovertwowidthsq (iKmax - iKmin + 1);
    for (iK = iKmin; iK <= iKmax; ++iK)
      oneovertwowidthsq[iK - iKmin] = 1.0/(2.0 * gwidth[iK - iKmin] * gwidth[iK - iKmin]);

    // Reset proper normalization:
    Vect_DP normalization_used (iKmax - iKmin + 1);
    for (iK = iKmin; iK <= iKmax; ++iK)
      normalization_used[iK - iKmin] = normalization * 1.0/(sqrt(twoPI) * gwidth[iK - iKmin]); // Gaussian factor

    DP FFsq = 0.0;
    while (RAW_infile.peek() != EOF) {
      RAW_infile >> omega >> iK >> FF >> dev >> label;
      if (iK >= iKmin && iK <= iKmax && fabs(omega) > 1.0e-8) { // remove connected part of DSF
	FFsq = FF * FF;
	SSF[iK - iKmin] += FFsq;
	for (int iomega = 0; iomega < Nom; ++iomega)
	  if (big_gwidth_used[iK - iKmin] > (d_omega = fabs(omegaout[iomega] - omega)))
	    for (int deltaiK = -DiK; deltaiK <= DiK; ++deltaiK)
	      if (iK + deltaiK >= iKmin && iK + deltaiK <= iKmax)
		DSFS[iomega][iK + deltaiK - iKmin] += Kweight[abs(deltaiK)] * FFsq * normalization_used[iK + deltaiK - iKmin]
		  * exp(-d_omega*d_omega * oneovertwowidthsq[iK + deltaiK - iKmin]);
      }
    }
    RAW_infile.close();

    // Reset proper normalization:
    for (int iK = 0; iK < iKmax - iKmin + 1; ++iK) {
      SSF[iK] *= normalization/twoPI;
    }

    // Output to .dsfs and .ssf files
    stringstream DSFS_stringstream;    string DSFS_string;
    DSFS_stringstream << prefix;
    if (DiK > 0) DSFS_stringstream << "_DiK_" << DiK;
    DSFS_stringstream << "_ommin_"<< ommin << "_ommax_" << ommax << "_Nom_" << Nom << "_w_" << width << ".dsfs";
    DSFS_string = DSFS_stringstream.str();    const char* DSFS_Cstr = DSFS_string.c_str();

    ofstream DSFS_outfile;
    DSFS_outfile.open(DSFS_Cstr);
    DSFS_outfile.precision(12);

    for (int iomega = 0; iomega < Nom; ++iomega) {
      if (iomega > 0) DSFS_outfile << endl;
      for (int iK = 0; iK < iKmax - iKmin + 1; ++iK)
	DSFS_outfile << DSFS[iomega][iK] << "\t";
    }
    DSFS_outfile.close();


    stringstream SSF_stringstream;    string SSF_string;
    SSF_stringstream << prefix;
    SSF_stringstream << ".ssf";
    SSF_string = SSF_stringstream.str();    const char* SSF_Cstr = SSF_string.c_str();

    ofstream SSF_outfile;
    SSF_outfile.open(SSF_Cstr);
    SSF_outfile.precision(12);

    for (int iK = 0; iK < iKmax - iKmin + 1; ++iK) {
      SSF_outfile << iK + iKmin << "\t" << SSF[iK] << endl;
    }
    SSF_outfile.close();


    // Check sums:
    DP sumdsf = 0.0;
    for (int iK = 0; iK < iKmax - iKmin + 1; ++iK) {
      for (int iomega = 0; iomega < Nom; ++iomega)
	sumdsf += DSFS[iomega][iK];
    }
    sumdsf /= (iKmax - iKmin + 1) * Nom;

    return(sumdsf);

  }

} // namespace ABACUS