grav_external.cc

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/*******************************************************************************
 * \copyright   This file is part of the GADGET4 N-body/SPH code developed
 * \copyright   by Volker Springel. Copyright (C) 2014-2020 by Volker Springel
 * \copyright   (vspringel@mpa-garching.mpg.de) and all contributing authors.
 *******************************************************************************/
 
#include "gadgetconfig.h"
 
#ifdef EXTERNALGRAVITY
 
#include <math.h>
#include <mpi.h>
#include <stdlib.h>
#include <string.h>
 
#include "../data/allvars.h"
#include "../data/dtypes.h"
#include "../data/intposconvert.h"
#include "../data/mymalloc.h"
#include "../domain/domain.h"
#include "../fmm/fmm.h"
#include "../gravtree/gravtree.h"
#include "../logs/logs.h"
#include "../logs/timer.h"
#include "../main/simulation.h"
#include "../mpi_utils/mpi_utils.h"
#include "../pm/pm.h"
#include "../system/system.h"
#include "../time_integration/timestep.h"
 
void sim::gravity_external(void)
{
  for(int i = 0; i < Sp.TimeBinsGravity.NActiveParticles; i++)
    {
      int target = Sp.TimeBinsGravity.ActiveParticleList[i];
 
#if defined(EVALPOTENTIAL) || defined(OUTPUT_POTENTIAL)
      Sp.P[target].ExtPotential = 0;
#endif
 
#ifdef EXTERNALGRAVITY_STATICHQ
      {
        vector<double> pos;
        Sp.intpos_to_pos(Sp.P[target].IntPos, pos.da); /* converts the integer coordinate to floating point */
 
        double r = sqrt(pos.r2());
 
        double m = All.Mass_StaticHQHalo * pow(r / (r + All.A_StaticHQHalo), 2);
 
        if(r > 0)
          Sp.P[target].GravAccel += (-All.G * m / (r * r * r)) * pos;
 
#if defined(EVALPOTENTIAL) || defined(OUTPUT_POTENTIAL)
        Sp.P[target].ExtPotential += (-All.G * All.Mass_StaticHQHalo / (r + All.A_StaticHQHalo));
#endif
      }
#endif
    }
}
 
#endif