src/mdlib/ewald.c

   1 /*
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   9  *                        VERSION 3.2.0
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  15  * This program is free software; you can redistribute it and/or
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  35 #ifdef HAVE_CONFIG_H
  36 #include <config.h>
  37 #endif
  38
  39 #include <stdio.h>
  40 #include <math.h>
  41 #include "typedefs.h"
  42 #include "vec.h"
  43 #include "gmxcomplex.h"
  44 #include "smalloc.h"
  45 #include "futil.h"
  46 #include "gmx_fatal.h"
  47 #include "physics.h"
  48 #include "coulomb.h"
  49
  50 #define TOL 2e-5
  51
  52 struct ewald_tab
  53 {
  54     int nx,ny,nz,kmax;
  55     cvec **eir;
  56     t_complex *tab_xy, *tab_qxyz;
  57 };
  58
  59
  60
  61 /* TODO: fix thread-safety */
  62
  63 /* the other routines are in complex.h */
  64 static t_complex conjmul(t_complex a,t_complex b)
  65 {
  66   t_complex c;
  67
  68   c.re = a.re*b.re + a.im*b.im;
  69   c.im = a.im*b.re - a.re*b.im;
  70
  71   return c;
  72 }
  73
  74
  75
  76
  77 static void tabulate_eir(int natom,rvec x[],int kmax,cvec **eir,rvec lll)
  78 {
  79   int  i,j,m;
  80
  81   if (kmax < 1) {
  82       printf("Go away! kmax = %d\n",kmax);
  83       exit(1);
  84   }
  85
  86   for(i=0; (i<natom); i++) {
  87     for(m=0; (m<3); m++) {
  88       eir[0][i][m].re = 1;
  89       eir[0][i][m].im = 0;
  90     }
  91
  92     for(m=0; (m<3); m++) {
  93       eir[1][i][m].re = cos(x[i][m]*lll[m]);
  94       eir[1][i][m].im = sin(x[i][m]*lll[m]);
  95     }
  96     for(j=2; (j<kmax); j++)
  97       for(m=0; (m<3); m++)
  98         eir[j][i][m] = cmul(eir[j-1][i][m],eir[1][i][m]);
  99   }
 100 }
 101
 102 void init_ewald_tab(ewald_tab_t *et, const t_commrec *cr, const t_inputrec *ir,
 103                     FILE *fp)
 104 {
 105     int n;
 106
 107     snew(*et, 1);
 108     if (fp)
 109         fprintf(fp,"Will do ordinary reciprocal space Ewald sum.\n");
 110
 111     (*et)->nx = ir->nkx+1;
 112     (*et)->ny = ir->nky+1;
 113     (*et)->nz = ir->nkz+1;
 114     (*et)->kmax = max((*et)->nx,max((*et)->ny,(*et)->nz));
 115     (*et)->eir = NULL;
 116     (*et)->tab_xy = NULL;
 117     (*et)->tab_qxyz = NULL;
 118 }
 119
 120
 121
 122 real do_ewald(FILE *log,       bool bVerbose,
 123               t_inputrec *ir,
 124               rvec x[],        rvec f[],
 125               real chargeA[],  real chargeB[],
 126               rvec box,
 127               t_commrec *cr,   int natoms,
 128               matrix lrvir,    real ewaldcoeff,
 129               real lambda,     real *dvdlambda,
 130               ewald_tab_t et)
 131 {
 132   real factor=-1.0/(4*ewaldcoeff*ewaldcoeff);
 133   real scaleRecip =4.0*M_PI/(box[XX]*box[YY]*box[ZZ])*ONE_4PI_EPS0/ir->epsilon_r; /* 1/(Vol*e0) */
 134   real *charge,energy_AB[2],energy;
 135   rvec lll;
 136   int  lowiy,lowiz,ix,iy,iz,n,q;
 137   real tmp,cs,ss,ak,akv,mx,my,mz,m2,scale;
 138   bool bFreeEnergy;
 139
 140     if (cr != NULL)
 141     {
 142         if (cr->nnodes > 1 || cr->nthreads>1)
 143             gmx_fatal(FARGS,"No parallel Ewald. Use PME instead.\n");
 144     }
 145
 146
 147   if (!et->eir) /* allocate if we need to */
 148   {
 149       snew(et->eir,et->kmax);
 150       for(n=0;n<et->kmax;n++)
 151           snew(et->eir[n],natoms);
 152       snew(et->tab_xy,natoms);
 153       snew(et->tab_qxyz,natoms);
 154   }
 155
 156   bFreeEnergy = (ir->efep != efepNO);
 157
 158   clear_mat(lrvir);
 159
 160   calc_lll(box,lll);
 161   /* make tables for the structure factor parts */
 162   tabulate_eir(natoms,x,et->kmax,et->eir,lll);
 163
 164   for(q=0; q<(bFreeEnergy ? 2 : 1); q++) {
 165     if (!bFreeEnergy) {
 166       charge = chargeA;
 167       scale = 1.0;
 168     } else if (q==0) {
 169       charge = chargeA;
 170       scale = 1.0 - lambda;
 171     } else {
 172       charge = chargeB;
 173       scale = lambda;
 174     }
 175     lowiy=0;
 176     lowiz=1;
 177     energy_AB[q]=0;
 178     for(ix=0;ix<et->nx;ix++) {
 179       mx=ix*lll[XX];
 180       for(iy=lowiy;iy<et->ny;iy++) {
 181         my=iy*lll[YY];
 182         if(iy>=0)
 183           for(n=0;n<natoms;n++)
 184             et->tab_xy[n]=cmul(et->eir[ix][n][XX],et->eir[iy][n][YY]);
 185         else
 186           for(n=0;n<natoms;n++)
 187             et->tab_xy[n]=conjmul(et->eir[ix][n][XX],et->eir[-iy][n][YY]);
 188         for(iz=lowiz;iz<et->nz;iz++) {
 189           mz=iz*lll[ZZ];
 190           m2=mx*mx+my*my+mz*mz;
 191           ak=exp(m2*factor)/m2;
 192           akv=2.0*ak*(1.0/m2-factor);
 193           if(iz>=0)
 194             for(n=0;n<natoms;n++)
 195               et->tab_qxyz[n]=rcmul(charge[n],cmul(et->tab_xy[n],
 196                                                    et->eir[iz][n][ZZ]));
 197           else
 198             for(n=0;n<natoms;n++)
 199               et->tab_qxyz[n]=rcmul(charge[n],conjmul(et->tab_xy[n],
 200                                                       et->eir[-iz][n][ZZ]));
 201
 202           cs=ss=0;
 203           for(n=0;n<natoms;n++) {
 204             cs+=et->tab_qxyz[n].re;
 205             ss+=et->tab_qxyz[n].im;
 206           }
 207           energy_AB[q]+=ak*(cs*cs+ss*ss);
 208           tmp=scale*akv*(cs*cs+ss*ss);
 209           lrvir[XX][XX]-=tmp*mx*mx;
 210           lrvir[XX][YY]-=tmp*mx*my;
 211           lrvir[XX][ZZ]-=tmp*mx*mz;
 212           lrvir[YY][YY]-=tmp*my*my;
 213           lrvir[YY][ZZ]-=tmp*my*mz;
 214           lrvir[ZZ][ZZ]-=tmp*mz*mz;
 215           for(n=0;n<natoms;n++) {
 216             /*tmp=scale*ak*(cs*tab_qxyz[n].im-ss*tab_qxyz[n].re);*/
 217             tmp=scale*ak*(cs*et->tab_qxyz[n].im-ss*et->tab_qxyz[n].re);
 218             f[n][XX]+=tmp*mx*2*scaleRecip;
 219             f[n][YY]+=tmp*my*2*scaleRecip;
 220             f[n][ZZ]+=tmp*mz*2*scaleRecip;
 221 #if 0
 222             f[n][XX]+=tmp*mx;
 223             f[n][YY]+=tmp*my;
 224             f[n][ZZ]+=tmp*mz;
 225 #endif
 226           }
 227           lowiz=1-et->nz;
 228         }
 229         lowiy=1-et->ny;
 230       }
 231     }
 232   }
 233
 234   if (!bFreeEnergy) {
 235     energy = energy_AB[0];
 236   } else {
 237     energy = (1.0 - lambda)*energy_AB[0] + lambda*energy_AB[1];
 238     *dvdlambda += scaleRecip*(energy_AB[1] - energy_AB[0]);
 239   }
 240
 241   lrvir[XX][XX]=-0.5*scaleRecip*(lrvir[XX][XX]+energy);
 242   lrvir[XX][YY]=-0.5*scaleRecip*(lrvir[XX][YY]);
 243   lrvir[XX][ZZ]=-0.5*scaleRecip*(lrvir[XX][ZZ]);
 244   lrvir[YY][YY]=-0.5*scaleRecip*(lrvir[YY][YY]+energy);
 245   lrvir[YY][ZZ]=-0.5*scaleRecip*(lrvir[YY][ZZ]);
 246   lrvir[ZZ][ZZ]=-0.5*scaleRecip*(lrvir[ZZ][ZZ]+energy);
 247
 248   lrvir[YY][XX]=lrvir[XX][YY];
 249   lrvir[ZZ][XX]=lrvir[XX][ZZ];
 250   lrvir[ZZ][YY]=lrvir[YY][ZZ];
 251
 252   energy*=scaleRecip;
 253
 254   return energy;
 255 }