potentials/albe_fast.c

   1 /*
   2  * test: albe_new.c
   3  *
   4  * author: Frank Zirkelbach <frank.zirkelbach@physik.uni-augsburg.de>
   5  *
   6  */
   7
   8 #define _GNU_SOURCE
   9 #include <stdio.h>
  10 #include <stdlib.h>
  11 #include <string.h>
  12 #include <sys/types.h>
  13 #include <sys/stat.h>
  14 #include <fcntl.h>
  15 #include <unistd.h>
  16 #include <sys/time.h>
  17 #include <time.h>
  18 #include <math.h>
  19
  20 #ifdef PARALLEL
  21 #include <omp.h>
  22 #endif
  23
  24 #ifdef PTHREADS
  25 #include <pthread.h>
  26 #define MAX_THREADS 4
  27 #endif
  28
  29 #include "../moldyn.h"
  30 #include "../math/math.h"
  31 #include "albe.h"
  32
  33 #ifdef PTHREADS
  34 extern pthread_mutex_t *amutex;
  35 extern pthread_mutex_t emutex;
  36 #endif
  37
  38 /*
  39  * virial calculation
  40  */
  41
  42 #define albe_v_calc(a,f,d)      a->virial.xx+=f->x*d->x; \
  43                                 a->virial.yy+=f->y*d->y; \
  44                                 a->virial.zz+=f->z*d->z; \
  45                                 a->virial.xy+=f->x*d->y; \
  46                                 a->virial.xz+=f->x*d->z; \
  47                                 a->virial.yz+=f->y*d->z
  48
  49 #ifndef PTHREADS
  50
  51 int albe_potential_force_calc(t_moldyn *moldyn) {
  52
  53         int i,j,k,count;
  54         t_atom *itom,*jtom,*ktom;
  55         t_virial *virial;
  56         t_linkcell *lc;
  57 #ifdef STATIC_LISTS
  58         int *neighbour_i[27];
  59         int p,q;
  60 #elif LOWMEM_LISTS
  61         int neighbour_i[27];
  62         int p,q;
  63 #else
  64         t_list neighbour_i[27];
  65         t_list neighbour_i2[27];
  66         t_list *this,*that;
  67 #endif
  68         u8 bc_ij,bc_ik;
  69         int dnlc;
  70 #ifdef PTHREADS
  71         int ret;
  72         t_kdata kdata[27];
  73         pthread_t kthread[27];
  74 #endif
  75
  76         // needed to work
  77         t_atom *ai;
  78
  79         // optimized
  80         t_albe_mult_params *params;
  81         t_albe_exchange *exchange;
  82         t_3dvec dist_ij;
  83         double d_ij2;
  84         double d_ij;
  85         u8 brand_i;
  86         double S2;
  87         int kcount;
  88         double zeta_ij;
  89         double pre_dzeta;
  90
  91         // more ...
  92         double Rk,Sk,Sk2;
  93         t_3dvec dist_ik;
  94         double d_ik2,d_ik;
  95         double cos_theta,h_cos,d2_h_cos2,frac,g,dg,s_r,arg;
  96         double f_c_ik,df_c_ik;
  97
  98         t_3dvec force;
  99         double f_a,df_a,b,db,f_c,df_c;
 100         double f_r,df_r;
 101         double scale;
 102         double mu,B;
 103         double lambda,A;
 104         double r0;
 105         double S,R;
 106         double energy;
 107
 108         double dijdik_inv,fcdg,dfcg;
 109         t_3dvec dcosdrj,dcosdrk;
 110         t_3dvec tmp;
 111
 112         // even more ...
 113         double gamma_i;
 114         double c_i;
 115         double d_i;
 116         double h_i;
 117         double ci2;
 118         double di2;
 119         double ci2di2;
 120
 121         count=moldyn->count;
 122         itom=moldyn->atom;
 123         lc=&(moldyn->lc);
 124
 125         // optimized
 126         params=moldyn->pot_params;
 127         exchange=&(params->exchange);
 128
 129
 130         /* reset energy */
 131         moldyn->energy=0.0;
 132
 133         /* reset global virial */
 134         memset(&(moldyn->gvir),0,sizeof(t_virial));
 135
 136         /* reset force, site energy and virial of every atom */
 137 #ifdef PARALLEL
 138         #pragma omp parallel for private(virial)
 139 #endif
 140         for(i=0;i<count;i++) {
 141
 142                 /* reset force */
 143                 v3_zero(&(itom[i].f));
 144
 145                 /* reset virial */
 146                 virial=(&(itom[i].virial));
 147                 virial->xx=0.0;
 148                 virial->yy=0.0;
 149                 virial->zz=0.0;
 150                 virial->xy=0.0;
 151                 virial->xz=0.0;
 152                 virial->yz=0.0;
 153
 154                 /* reset site energy */
 155                 itom[i].e=0.0;
 156
 157         }
 158
 159         /* get energy, force and virial of every atom */
 160
 161         /* first (and only) loop over atoms i */
 162         for(i=0;i<count;i++) {
 163
 164                 if(!(itom[i].attr&ATOM_ATTR_3BP))
 165                         continue;
 166
 167                 link_cell_neighbour_index(moldyn,
 168                                           (itom[i].r.x+moldyn->dim.x/2)/lc->x,
 169                                           (itom[i].r.y+moldyn->dim.y/2)/lc->y,
 170                                           (itom[i].r.z+moldyn->dim.z/2)/lc->z,
 171                                           neighbour_i);
 172
 173                 dnlc=lc->dnlc;
 174
 175                 /* copy the neighbour lists */
 176 #ifdef STATIC_LISTS
 177 #elif LOWMEM_LISTS
 178 #else
 179                 memcpy(neighbour_i2,neighbour_i,27*sizeof(t_list));
 180 #endif
 181
 182                 ai=&(itom[i]);
 183                 brand_i=ai->brand;
 184
 185                 /* loop over atoms j */
 186                 for(j=0;j<27;j++) {
 187
 188                         bc_ij=(j<dnlc)?0:1;
 189 #ifdef STATIC_LISTS
 190                         p=0;
 191
 192                         while(neighbour_i[j][p]!=-1) {
 193
 194                                 jtom=&(itom[neighbour_i[j][p]]);
 195                                 p++;
 196 #elif LOWMEM_LISTS
 197                         p=neighbour_i[j];
 198
 199                         while(p!=-1) {
 200
 201                                 jtom=&(itom[p]);
 202                                 p=lc->subcell->list[p];
 203 #else
 204                         this=&(neighbour_i[j]);
 205                         list_reset_f(this);
 206
 207                         if(this->start==NULL)
 208                                 continue;
 209
 210                         do {
 211
 212                                 jtom=this->current->data;
 213 #endif
 214
 215                                 if(jtom==&(itom[i]))
 216                                         continue;
 217
 218                                 if(!(jtom->attr&ATOM_ATTR_3BP))
 219                                         continue;
 220
 221                                 /* reset 3bp run */
 222                                 moldyn->run3bp=1;
 223
 224
 225 /* j1 func here ... */
 226 /* albe 3 body potential function (first ij loop) */
 227
 228         /* reset zeta sum */
 229         zeta_ij=0.0;
 230
 231         /*
 232          * set ij depending values
 233          */
 234
 235         if(brand_i==jtom->brand) {
 236                 S2=params->S2[brand_i];
 237         }
 238         else {
 239                 S2=params->S2mixed;
 240         }
 241
 242         /* dist_ij, d_ij2 */
 243         v3_sub(&dist_ij,&(jtom->r),&(ai->r));
 244         if(bc_ij) check_per_bound(moldyn,&dist_ij);
 245         d_ij2=v3_absolute_square(&dist_ij);
 246
 247         /* if d_ij2 > S2 => no force & potential energy contribution */
 248         if(d_ij2>S2)
 249                 continue;
 250
 251         /* d_ij */
 252         d_ij=sqrt(d_ij2);
 253
 254         /* reset k counter for first k loop */
 255         kcount=0;
 256
 257                                 /* first loop over atoms k */
 258                                 for(k=0;k<27;k++) {
 259
 260                                         bc_ik=(k<dnlc)?0:1;
 261 #ifdef STATIC_LISTS
 262                                         q=0;
 263
 264                                         while(neighbour_i[k][q]!=-1) {
 265
 266                                                 ktom=&(itom[neighbour_i[k][q]]);
 267                                                 q++;
 268 #elif LOWMEM_LISTS
 269                                         q=neighbour_i[k];
 270
 271                                         while(q!=-1) {
 272
 273                                                 ktom=&(itom[q]);
 274                                                 q=lc->subcell->list[q];
 275 #else
 276                                         that=&(neighbour_i2[k]);
 277                                         list_reset_f(that);
 278
 279                                         if(that->start==NULL)
 280                                                 continue;
 281
 282                                         do {
 283                                                 ktom=that->current->data;
 284 #endif
 285
 286                                                 if(!(ktom->attr&ATOM_ATTR_3BP))
 287                                                         continue;
 288
 289                                                 if(ktom==jtom)
 290                                                         continue;
 291
 292                                                 if(ktom==&(itom[i]))
 293                                                         continue;
 294
 295 /* k1 func here ... */
 296 /* albe 3 body potential function (first k loop) */
 297
 298         if(kcount>ALBE_MAXN) {
 299                 printf("FATAL: neighbours = %d\n",kcount);
 300                 printf("  -> %d %d %d\n",ai->tag,jtom->tag,ktom->tag);
 301         }
 302
 303         /* ik constants */
 304         if(brand_i==ktom->brand) {
 305                 Rk=params->R[brand_i];
 306                 Sk=params->S[brand_i];
 307                 Sk2=params->S2[brand_i];
 308                 /* albe needs i,k depending c,d,h and gamma values */
 309                 gamma_i=params->gamma[brand_i];
 310                 c_i=params->c[brand_i];
 311                 d_i=params->d[brand_i];
 312                 h_i=params->h[brand_i];
 313                 ci2=params->c2[brand_i];
 314                 di2=params->d2[brand_i];
 315                 ci2di2=params->c2d2[brand_i];
 316         }
 317         else {
 318                 Rk=params->Rmixed;
 319                 Sk=params->Smixed;
 320                 Sk2=params->S2mixed;
 321                 /* albe needs i,k depending c,d,h and gamma values */
 322                 gamma_i=params->gamma_m;
 323                 c_i=params->c_mixed;
 324                 d_i=params->d_mixed;
 325                 h_i=params->h_mixed;
 326                 ci2=params->c2_mixed;
 327                 di2=params->d2_mixed;
 328                 ci2di2=params->c2d2_m;
 329         }
 330
 331         /* dist_ik, d_ik2 */
 332         v3_sub(&dist_ik,&(ktom->r),&(ai->r));
 333         if(bc_ik) check_per_bound(moldyn,&dist_ik);
 334         d_ik2=v3_absolute_square(&dist_ik);
 335
 336         /* store data for second k loop */
 337         exchange->dist_ik[kcount]=dist_ik;
 338         exchange->d_ik2[kcount]=d_ik2;
 339
 340         /* return if not within cutoff */
 341         if(d_ik2>Sk2) {
 342                 kcount++;
 343                 continue;
 344         }
 345
 346         /* d_ik */
 347         d_ik=sqrt(d_ik2);
 348
 349         /* cos theta */
 350         cos_theta=v3_scalar_product(&dist_ij,&dist_ik)/(d_ij*d_ik);
 351
 352         /* g_ijk
 353         h_cos=*(exchange->h_i)+cos_theta; // + in albe formalism
 354         d2_h_cos2=exchange->di2+(h_cos*h_cos);
 355         frac=exchange->ci2/d2_h_cos2;
 356         g=*(exchange->gamma_i)*(1.0+exchange->ci2di2-frac);
 357         dg=2.0*frac**(exchange->gamma_i)*h_cos/d2_h_cos2; // + in albe f..
 358         */
 359
 360         h_cos=h_i+cos_theta; // + in albe formalism
 361         d2_h_cos2=di2+(h_cos*h_cos);
 362         frac=ci2/d2_h_cos2;
 363         g=gamma_i*(1.0+ci2di2-frac);
 364         dg=2.0*frac*gamma_i*h_cos/d2_h_cos2; // + in albe f..
 365
 366         /* zeta sum += f_c_ik * g_ijk */
 367         if(d_ik<=Rk) {
 368                 zeta_ij+=g;
 369                 f_c_ik=1.0;
 370                 df_c_ik=0.0;
 371         }
 372         else {
 373                 s_r=Sk-Rk;
 374                 arg=M_PI*(d_ik-Rk)/s_r;
 375                 f_c_ik=0.5+0.5*cos(arg);
 376                 df_c_ik=0.5*sin(arg)*(M_PI/(s_r*d_ik));
 377                 zeta_ij+=f_c_ik*g;
 378         }
 379
 380         /* store even more data for second k loop */
 381         exchange->g[kcount]=g;
 382         exchange->dg[kcount]=dg;
 383         exchange->d_ik[kcount]=d_ik;
 384         exchange->cos_theta[kcount]=cos_theta;
 385         exchange->f_c_ik[kcount]=f_c_ik;
 386         exchange->df_c_ik[kcount]=df_c_ik;
 387
 388         /* increase k counter */
 389         kcount++;
 390
 391 #ifdef STATIC_LISTS
 392                                         }
 393 #elif LOWMEM_LISTS
 394                                         }
 395 #else
 396                                         } while(list_next_f(that)!=\
 397                                                 L_NO_NEXT_ELEMENT);
 398 #endif
 399
 400                                 }
 401
 402 /* j2 func here ... */
 403
 404
 405         if(brand_i==jtom->brand) {
 406                 S=params->S[brand_i];
 407                 R=params->R[brand_i];
 408                 B=params->B[brand_i];
 409                 A=params->A[brand_i];
 410                 r0=params->r0[brand_i];
 411                 mu=params->mu[brand_i];
 412                 lambda=params->lambda[brand_i];
 413         }
 414         else {
 415                 S=params->Smixed;
 416                 R=params->Rmixed;
 417                 B=params->Bmixed;
 418                 A=params->Amixed;
 419                 r0=params->r0_mixed;
 420                 mu=params->mu_m;
 421                 lambda=params->lambda_m;
 422         }
 423
 424         /* f_c, df_c */
 425         if(d_ij<R) {
 426                 f_c=1.0;
 427                 df_c=0.0;
 428         }
 429         else {
 430                 s_r=S-R;
 431                 arg=M_PI*(d_ij-R)/s_r;
 432                 f_c=0.5+0.5*cos(arg);
 433                 df_c=0.5*sin(arg)*(M_PI/(s_r*d_ij));
 434         }
 435
 436         /* f_a, df_a */
 437         f_a=-B*exp(-mu*(d_ij-r0));
 438         df_a=mu*f_a/d_ij;
 439
 440         /* f_r, df_r */
 441         f_r=A*exp(-lambda*(d_ij-r0));
 442         df_r=lambda*f_r/d_ij;
 443
 444         /* b, db */
 445         if(zeta_ij==0.0) {
 446                 b=1.0;
 447                 db=0.0;
 448         }
 449         else {
 450                 b=1.0/sqrt(1.0+zeta_ij);
 451                 db=-0.5*b/(1.0+zeta_ij);
 452         }
 453
 454         /* force contribution for atom i */
 455         scale=-0.5*(f_c*(df_r-b*df_a)+df_c*(f_r-b*f_a)); // - in albe formalism
 456         v3_scale(&force,&(dist_ij),scale);
 457         v3_add(&(ai->f),&(ai->f),&force);
 458
 459         /* force contribution for atom j */
 460         v3_scale(&force,&force,-1.0); // dri rij = - drj rij
 461         v3_add(&(jtom->f),&(jtom->f),&force);
 462
 463         /* virial */
 464         virial_calc(ai,&force,&(dist_ij));
 465
 466 #ifdef DEBUG
 467 if(moldyn->time>DSTART&&moldyn->time<DEND) {
 468         if((ai==&(moldyn->atom[DATOM]))|(jtom==&(moldyn->atom[DATOM]))) {
 469                 printf("force 3bp (j2): [%d %d sum]\n",ai->tag,jtom->tag);
 470                 printf("  adding %f %f %f\n",force.x,force.y,force.z);
 471                 if(ai==&(moldyn->atom[0]))
 472                         printf("  total i: %f %f %f\n",ai->f.x,ai->f.y,ai->f.z);
 473                 if(jtom==&(moldyn->atom[0]))
 474                         printf("  total j: %f %f %f\n",jtom->f.x,jtom->f.y,jtom->f.z);
 475                 printf("  energy: %f = %f %f %f %f\n",0.5*f_c*(b*f_a+f_r),
 476                                                     f_c,b,f_a,f_r);
 477                 printf("          %f %f %f\n",zeta_ij,.0,.0);
 478         }
 479 }
 480 #endif
 481
 482         /* dzeta prefactor = - f_c f_a db, (* -0.5 due to force calc) */
 483         pre_dzeta=0.5*f_a*f_c*db;
 484
 485         /* energy contribution */
 486         energy=0.5*f_c*(f_r-b*f_a); // - in albe formalism
 487         moldyn->energy+=energy;
 488         ai->e+=energy;
 489
 490         /* reset k counter for second k loop */
 491         kcount=0;
 492
 493
 494                                 /* second loop over atoms k */
 495                                 for(k=0;k<27;k++) {
 496
 497                                         bc_ik=(k<dnlc)?0:1;
 498 #ifdef STATIC_LISTS
 499                                         q=0;
 500
 501                                         while(neighbour_i[k][q]!=-1) {
 502
 503                                                 ktom=&(itom[neighbour_i[k][q]]);
 504                                                 q++;
 505 #elif LOWMEM_LISTS
 506                                         q=neighbour_i[k];
 507
 508                                         while(q!=-1) {
 509
 510                                                 ktom=&(itom[q]);
 511                                                 q=lc->subcell->list[q];
 512 #else
 513                                         that=&(neighbour_i2[k]);
 514                                         list_reset_f(that);
 515
 516                                         if(that->start==NULL)
 517                                                 continue;
 518
 519                                         do {
 520                                                 ktom=that->current->data;
 521 #endif
 522
 523                                                 if(!(ktom->attr&ATOM_ATTR_3BP))
 524                                                         continue;
 525
 526                                                 if(ktom==jtom)
 527                                                         continue;
 528
 529                                                 if(ktom==&(itom[i]))
 530                                                         continue;
 531
 532
 533 /* k2 func here ... */
 534 /* albe 3 body potential function (second k loop) */
 535
 536         if(kcount>ALBE_MAXN)
 537                 printf("FATAL: neighbours!\n");
 538
 539         /* d_ik2 */
 540         d_ik2=exchange->d_ik2[kcount];
 541
 542         if(brand_i==ktom->brand)
 543                 Sk2=params->S2[brand_i];
 544         else
 545                 Sk2=params->S2mixed;
 546
 547         /* return if d_ik > S */
 548         if(d_ik2>Sk2) {
 549                 kcount++;
 550                 continue;
 551         }
 552
 553         /* dist_ik, d_ik */
 554         dist_ik=exchange->dist_ik[kcount];
 555         d_ik=exchange->d_ik[kcount];
 556
 557         /* f_c_ik, df_c_ik */
 558         f_c_ik=exchange->f_c_ik[kcount];
 559         df_c_ik=exchange->df_c_ik[kcount];
 560
 561         /* g, dg, cos_theta */
 562         g=exchange->g[kcount];
 563         dg=exchange->dg[kcount];
 564         cos_theta=exchange->cos_theta[kcount];
 565
 566         /* cos_theta derivatives wrt j,k */
 567         dijdik_inv=1.0/(d_ij*d_ik);
 568         v3_scale(&dcosdrj,&dist_ik,dijdik_inv);         // j
 569         v3_scale(&tmp,&dist_ij,-cos_theta/d_ij2);
 570         v3_add(&dcosdrj,&dcosdrj,&tmp);
 571         v3_scale(&dcosdrk,&dist_ij,dijdik_inv);         // k
 572         v3_scale(&tmp,&dist_ik,-cos_theta/d_ik2);
 573         v3_add(&dcosdrk,&dcosdrk,&tmp);
 574
 575         /* f_c_ik * dg, df_c_ik * g */
 576         fcdg=f_c_ik*dg;
 577         dfcg=df_c_ik*g;
 578
 579         /* derivative wrt j */
 580         v3_scale(&force,&dcosdrj,fcdg*pre_dzeta);
 581
 582         /* force contribution */
 583         v3_add(&(jtom->f),&(jtom->f),&force);
 584
 585 #ifdef DEBUG
 586 if(moldyn->time>DSTART&&moldyn->time<DEND) {
 587         if(jtom==&(moldyn->atom[DATOM])) {
 588                 printf("force 3bp (k2): [%d %d %d]\n",ai->tag,jtom->tag,ktom->tag);
 589                 printf("  adding %f %f %f\n",force.x,force.y,force.z);
 590                 printf("  total j: %f %f %f\n",jtom->f.x,jtom->f.y,jtom->f.z);
 591                 printf("  angle: %f\n",acos(cos_theta)*360.0/(2*M_PI));
 592                 printf("    d ij ik = %f %f\n",d_ij,d_ik);
 593         }
 594 }
 595 #endif
 596
 597         /* virial */
 598         virial_calc(ai,&force,&dist_ij);
 599
 600         /* force contribution to atom i */
 601         v3_scale(&force,&force,-1.0);
 602         v3_add(&(ai->f),&(ai->f),&force);
 603
 604         /* derivative wrt k */
 605         v3_scale(&force,&dist_ik,-1.0*dfcg); // dri rik = - drk rik
 606         v3_scale(&tmp,&dcosdrk,fcdg);
 607         v3_add(&force,&force,&tmp);
 608         v3_scale(&force,&force,pre_dzeta);
 609
 610         /* force contribution */
 611         v3_add(&(ktom->f),&(ktom->f),&force);
 612
 613 #ifdef DEBUG
 614 if(moldyn->time>DSTART&&moldyn->time<DEND) {
 615         if(ktom==&(moldyn->atom[DATOM])) {
 616                 printf("force 3bp (k2): [%d %d %d]\n",ai->tag,jtom->tag,ktom->tag);
 617                 printf("  adding %f %f %f\n",force.x,force.y,force.z);
 618                 printf("  total k: %f %f %f\n",ktom->f.x,ktom->f.y,ktom->f.z);
 619                 printf("  angle: %f\n",acos(cos_theta)*360.0/(2*M_PI));
 620                 printf("    d ij ik = %f %f\n",d_ij,d_ik);
 621         }
 622 }
 623 #endif
 624
 625         /* virial */
 626         virial_calc(ai,&force,&dist_ik);
 627
 628         /* force contribution to atom i */
 629         v3_scale(&force,&force,-1.0);
 630         v3_add(&(ai->f),&(ai->f),&force);
 631
 632         /* increase k counter */
 633         kcount++;
 634
 635
 636
 637 #ifdef STATIC_LISTS
 638                                         }
 639 #elif LOWMEM_LISTS
 640                                         }
 641 #else
 642                                         } while(list_next_f(that)!=\
 643                                                 L_NO_NEXT_ELEMENT);
 644 #endif
 645
 646                                 }
 647
 648 #ifdef STATIC_LISTS
 649                         }
 650 #elif LOWMEM_LISTS
 651                         }
 652 #else
 653                         } while(list_next_f(this)!=L_NO_NEXT_ELEMENT);
 654 #endif
 655
 656                 }
 657
 658 #ifdef DEBUG
 659         //printf("\n\n");
 660 #endif
 661 #ifdef VDEBUG
 662         printf("\n\n");
 663 #endif
 664
 665         }
 666
 667 #ifdef DEBUG
 668         //printf("\nATOM 0: %f %f %f\n\n",itom->f.x,itom->f.y,itom->f.z);
 669         if(moldyn->time>DSTART&&moldyn->time<DEND) {
 670                 printf("force:\n");
 671                 printf("  x: %0.40f\n",moldyn->atom[DATOM].f.x);
 672                 printf("  y: %0.40f\n",moldyn->atom[DATOM].f.y);
 673                 printf("  z: %0.40f\n",moldyn->atom[DATOM].f.z);
 674         }
 675 #endif
 676
 677         /* some postprocessing */
 678 #ifdef PARALLEL
 679         #pragma omp parallel for
 680 #endif
 681         for(i=0;i<count;i++) {
 682                 /* calculate global virial */
 683                 moldyn->gvir.xx+=itom[i].r.x*itom[i].f.x;
 684                 moldyn->gvir.yy+=itom[i].r.y*itom[i].f.y;
 685                 moldyn->gvir.zz+=itom[i].r.z*itom[i].f.z;
 686                 moldyn->gvir.xy+=itom[i].r.y*itom[i].f.x;
 687                 moldyn->gvir.xz+=itom[i].r.z*itom[i].f.x;
 688                 moldyn->gvir.yz+=itom[i].r.z*itom[i].f.y;
 689
 690                 /* check forces regarding the given timestep */
 691                 if(v3_norm(&(itom[i].f))>\
 692                    0.1*moldyn->nnd*itom[i].mass/moldyn->tau_square)
 693                         printf("[moldyn] WARNING: pfc (high force: atom %d)\n",
 694                                i);
 695         }
 696
 697         return 0;
 698 }
 699
 700
 701 #else // PTHREADS
 702
 703
 704 typedef struct s_pft_data {
 705         t_moldyn *moldyn;
 706         int start,end;
 707 } t_pft_data;
 708
 709 void *potential_force_thread(void *ptr) {
 710
 711         t_pft_data *pft_data;
 712         t_moldyn *moldyn;
 713         t_albe_exchange ec;
 714
 715         int i,j,k,count;
 716         t_atom *itom,*jtom,*ktom;
 717         t_linkcell *lc;
 718 #ifdef STATIC_LISTS
 719         int *neighbour_i[27];
 720         int p,q;
 721 #elif LOWMEM_LISTS
 722         int neighbour_i[27];
 723         int p,q;
 724 #else
 725         t_list neighbour_i[27];
 726         t_list neighbour_i2[27];
 727         t_list *this,*that;
 728 #endif
 729         u8 bc_ij,bc_ik;
 730         int dnlc;
 731
 732         // needed to work
 733         t_atom *ai;
 734
 735         // optimized
 736         t_albe_mult_params *params;
 737         t_albe_exchange *exchange;
 738         t_3dvec dist_ij;
 739         double d_ij2;
 740         double d_ij;
 741         u8 brand_i;
 742         double S2;
 743         int kcount;
 744         double zeta_ij;
 745         double pre_dzeta;
 746
 747         // more ...
 748         double Rk,Sk,Sk2;
 749         t_3dvec dist_ik;
 750         double d_ik2,d_ik;
 751         double cos_theta,h_cos,d2_h_cos2,frac,g,dg,s_r,arg;
 752         double f_c_ik,df_c_ik;
 753
 754         t_3dvec force;
 755         double f_a,df_a,b,db,f_c,df_c;
 756         double f_r,df_r;
 757         double scale;
 758         double mu,B;
 759         double lambda,A;
 760         double r0;
 761         double S,R;
 762         double energy;
 763
 764         double dijdik_inv,fcdg,dfcg;
 765         t_3dvec dcosdrj,dcosdrk;
 766         t_3dvec tmp;
 767
 768         // even more ...
 769         double gamma_i;
 770         double c_i;
 771         double d_i;
 772         double h_i;
 773         double ci2;
 774         double di2;
 775         double ci2di2;
 776
 777         pft_data=ptr;
 778         moldyn=pft_data->moldyn;
 779         exchange=&ec;
 780
 781         count=moldyn->count;
 782         itom=moldyn->atom;
 783         lc=&(moldyn->lc);
 784
 785         // optimized
 786         params=moldyn->pot_params;
 787
 788         /* get energy, force and virial for atoms */
 789
 790         for(i=pft_data->start;i<pft_data->end;i++) {
 791
 792                 if(!(itom[i].attr&ATOM_ATTR_3BP))
 793                         return 0;
 794
 795                 link_cell_neighbour_index(moldyn,
 796                                           (itom[i].r.x+moldyn->dim.x/2)/lc->x,
 797                                           (itom[i].r.y+moldyn->dim.y/2)/lc->y,
 798                                           (itom[i].r.z+moldyn->dim.z/2)/lc->z,
 799                                           neighbour_i);
 800
 801                 dnlc=lc->dnlc;
 802
 803                 /* copy the neighbour lists */
 804 #ifdef STATIC_LISTS
 805 #elif LOWMEM_LISTS
 806 #else
 807                 memcpy(neighbour_i2,neighbour_i,27*sizeof(t_list));
 808 #endif
 809
 810                 ai=&(itom[i]);
 811                 brand_i=ai->brand;
 812
 813                 /* loop over atoms j */
 814                 for(j=0;j<27;j++) {
 815
 816                         bc_ij=(j<dnlc)?0:1;
 817 #ifdef STATIC_LISTS
 818                         p=0;
 819
 820                         while(neighbour_i[j][p]!=-1) {
 821
 822                                 jtom=&(itom[neighbour_i[j][p]]);
 823                                 p++;
 824 #elif LOWMEM_LISTS
 825                         p=neighbour_i[j];
 826
 827                         while(p!=-1) {
 828
 829                                 jtom=&(itom[p]);
 830                                 p=lc->subcell->list[p];
 831 #else
 832                         this=&(neighbour_i[j]);
 833                         list_reset_f(this);
 834
 835                         if(this->start==NULL)
 836                                 continue;
 837
 838                         do {
 839
 840                                 jtom=this->current->data;
 841 #endif
 842
 843                                 if(jtom==&(itom[i]))
 844                                         continue;
 845
 846                                 if(!(jtom->attr&ATOM_ATTR_3BP))
 847                                         continue;
 848
 849                                 /* reset 3bp run */
 850                                 moldyn->run3bp=1;
 851
 852
 853 /* j1 func here ... */
 854 /* albe 3 body potential function (first ij loop) */
 855
 856         /* reset zeta sum */
 857         zeta_ij=0.0;
 858
 859         /*
 860          * set ij depending values
 861          */
 862
 863         if(brand_i==jtom->brand) {
 864                 S2=params->S2[brand_i];
 865         }
 866         else {
 867                 S2=params->S2mixed;
 868         }
 869
 870         /* dist_ij, d_ij2 */
 871         v3_sub(&dist_ij,&(jtom->r),&(ai->r));
 872         if(bc_ij) check_per_bound(moldyn,&dist_ij);
 873         d_ij2=v3_absolute_square(&dist_ij);
 874
 875         /* if d_ij2 > S2 => no force & potential energy contribution */
 876         if(d_ij2>S2)
 877                 continue;
 878
 879         /* d_ij */
 880         d_ij=sqrt(d_ij2);
 881
 882         /* reset k counter for first k loop */
 883         kcount=0;
 884
 885                                 /* first loop over atoms k */
 886                                 for(k=0;k<27;k++) {
 887
 888                                         bc_ik=(k<dnlc)?0:1;
 889 #ifdef STATIC_LISTS
 890                                         q=0;
 891
 892                                         while(neighbour_i[k][q]!=-1) {
 893
 894                                                 ktom=&(itom[neighbour_i[k][q]]);
 895                                                 q++;
 896 #elif LOWMEM_LISTS
 897                                         q=neighbour_i[k];
 898
 899                                         while(q!=-1) {
 900
 901                                                 ktom=&(itom[q]);
 902                                                 q=lc->subcell->list[q];
 903 #else
 904                                         that=&(neighbour_i2[k]);
 905                                         list_reset_f(that);
 906
 907                                         if(that->start==NULL)
 908                                                 continue;
 909
 910                                         do {
 911                                                 ktom=that->current->data;
 912 #endif
 913
 914                                                 if(!(ktom->attr&ATOM_ATTR_3BP))
 915                                                         continue;
 916
 917                                                 if(ktom==jtom)
 918                                                         continue;
 919
 920                                                 if(ktom==&(itom[i]))
 921                                                         continue;
 922
 923 /* k1 func here ... */
 924 /* albe 3 body potential function (first k loop) */
 925
 926         if(kcount>ALBE_MAXN) {
 927                 printf("FATAL: neighbours = %d\n",kcount);
 928                 printf("  -> %d %d %d\n",ai->tag,jtom->tag,ktom->tag);
 929         }
 930
 931         /* ik constants */
 932         if(brand_i==ktom->brand) {
 933                 Rk=params->R[brand_i];
 934                 Sk=params->S[brand_i];
 935                 Sk2=params->S2[brand_i];
 936                 /* albe needs i,k depending c,d,h and gamma values */
 937                 gamma_i=params->gamma[brand_i];
 938                 c_i=params->c[brand_i];
 939                 d_i=params->d[brand_i];
 940                 h_i=params->h[brand_i];
 941                 ci2=params->c2[brand_i];
 942                 di2=params->d2[brand_i];
 943                 ci2di2=params->c2d2[brand_i];
 944         }
 945         else {
 946                 Rk=params->Rmixed;
 947                 Sk=params->Smixed;
 948                 Sk2=params->S2mixed;
 949                 /* albe needs i,k depending c,d,h and gamma values */
 950                 gamma_i=params->gamma_m;
 951                 c_i=params->c_mixed;
 952                 d_i=params->d_mixed;
 953                 h_i=params->h_mixed;
 954                 ci2=params->c2_mixed;
 955                 di2=params->d2_mixed;
 956                 ci2di2=params->c2d2_m;
 957         }
 958
 959         /* dist_ik, d_ik2 */
 960         v3_sub(&dist_ik,&(ktom->r),&(ai->r));
 961         if(bc_ik) check_per_bound(moldyn,&dist_ik);
 962         d_ik2=v3_absolute_square(&dist_ik);
 963
 964         /* store data for second k loop */
 965         exchange->dist_ik[kcount]=dist_ik;
 966         exchange->d_ik2[kcount]=d_ik2;
 967
 968         /* return if not within cutoff */
 969         if(d_ik2>Sk2) {
 970                 kcount++;
 971                 continue;
 972         }
 973
 974         /* d_ik */
 975         d_ik=sqrt(d_ik2);
 976
 977         /* cos theta */
 978         cos_theta=v3_scalar_product(&dist_ij,&dist_ik)/(d_ij*d_ik);
 979
 980         /* g_ijk
 981         h_cos=*(exchange->h_i)+cos_theta; // + in albe formalism
 982         d2_h_cos2=exchange->di2+(h_cos*h_cos);
 983         frac=exchange->ci2/d2_h_cos2;
 984         g=*(exchange->gamma_i)*(1.0+exchange->ci2di2-frac);
 985         dg=2.0*frac**(exchange->gamma_i)*h_cos/d2_h_cos2; // + in albe f..
 986         */
 987
 988         h_cos=h_i+cos_theta; // + in albe formalism
 989         d2_h_cos2=di2+(h_cos*h_cos);
 990         frac=ci2/d2_h_cos2;
 991         g=gamma_i*(1.0+ci2di2-frac);
 992         dg=2.0*frac*gamma_i*h_cos/d2_h_cos2; // + in albe f..
 993
 994         /* zeta sum += f_c_ik * g_ijk */
 995         if(d_ik<=Rk) {
 996                 zeta_ij+=g;
 997                 f_c_ik=1.0;
 998                 df_c_ik=0.0;
 999         }
1000         else {
1001                 s_r=Sk-Rk;
1002                 arg=M_PI*(d_ik-Rk)/s_r;
1003                 f_c_ik=0.5+0.5*cos(arg);
1004                 df_c_ik=0.5*sin(arg)*(M_PI/(s_r*d_ik));
1005                 zeta_ij+=f_c_ik*g;
1006         }
1007
1008         /* store even more data for second k loop */
1009         exchange->g[kcount]=g;
1010         exchange->dg[kcount]=dg;
1011         exchange->d_ik[kcount]=d_ik;
1012         exchange->cos_theta[kcount]=cos_theta;
1013         exchange->f_c_ik[kcount]=f_c_ik;
1014         exchange->df_c_ik[kcount]=df_c_ik;
1015
1016         /* increase k counter */
1017         kcount++;
1018
1019 #ifdef STATIC_LISTS
1020                                         }
1021 #elif LOWMEM_LISTS
1022                                         }
1023 #else
1024                                         } while(list_next_f(that)!=\
1025                                                 L_NO_NEXT_ELEMENT);
1026 #endif
1027
1028                                 }
1029
1030 /* j2 func here ... */
1031
1032
1033         if(brand_i==jtom->brand) {
1034                 S=params->S[brand_i];
1035                 R=params->R[brand_i];
1036                 B=params->B[brand_i];
1037                 A=params->A[brand_i];
1038                 r0=params->r0[brand_i];
1039                 mu=params->mu[brand_i];
1040                 lambda=params->lambda[brand_i];
1041         }
1042         else {
1043                 S=params->Smixed;
1044                 R=params->Rmixed;
1045                 B=params->Bmixed;
1046                 A=params->Amixed;
1047                 r0=params->r0_mixed;
1048                 mu=params->mu_m;
1049                 lambda=params->lambda_m;
1050         }
1051
1052         /* f_c, df_c */
1053         if(d_ij<R) {
1054                 f_c=1.0;
1055                 df_c=0.0;
1056         }
1057         else {
1058                 s_r=S-R;
1059                 arg=M_PI*(d_ij-R)/s_r;
1060                 f_c=0.5+0.5*cos(arg);
1061                 df_c=0.5*sin(arg)*(M_PI/(s_r*d_ij));
1062         }
1063
1064         /* f_a, df_a */
1065         f_a=-B*exp(-mu*(d_ij-r0));
1066         df_a=mu*f_a/d_ij;
1067
1068         /* f_r, df_r */
1069         f_r=A*exp(-lambda*(d_ij-r0));
1070         df_r=lambda*f_r/d_ij;
1071
1072         /* b, db */
1073         if(zeta_ij==0.0) {
1074                 b=1.0;
1075                 db=0.0;
1076         }
1077         else {
1078                 b=1.0/sqrt(1.0+zeta_ij);
1079                 db=-0.5*b/(1.0+zeta_ij);
1080         }
1081
1082         /* force contribution for atom i */
1083         scale=-0.5*(f_c*(df_r-b*df_a)+df_c*(f_r-b*f_a)); // - in albe formalism
1084         v3_scale(&force,&(dist_ij),scale);
1085         pthread_mutex_lock(&(amutex[ai->tag]));
1086         v3_add(&(ai->f),&(ai->f),&force);
1087         pthread_mutex_unlock(&(amutex[ai->tag]));
1088
1089         /* force contribution for atom j */
1090         v3_scale(&force,&force,-1.0); // dri rij = - drj rij
1091         pthread_mutex_lock(&(amutex[jtom->tag]));
1092         v3_add(&(jtom->f),&(jtom->f),&force);
1093         pthread_mutex_unlock(&(amutex[jtom->tag]));
1094
1095         /* virial */
1096         pthread_mutex_lock(&(amutex[ai->tag]));
1097         virial_calc(ai,&force,&(dist_ij));
1098         pthread_mutex_unlock(&(amutex[ai->tag]));
1099
1100 #ifdef DEBUG
1101 if(moldyn->time>DSTART&&moldyn->time<DEND) {
1102         if((ai==&(moldyn->atom[DATOM]))|(jtom==&(moldyn->atom[DATOM]))) {
1103                 printf("force 3bp (j2): [%d %d sum]\n",ai->tag,jtom->tag);
1104                 printf("  adding %f %f %f\n",force.x,force.y,force.z);
1105                 if(ai==&(moldyn->atom[0]))
1106                         printf("  total i: %f %f %f\n",ai->f.x,ai->f.y,ai->f.z);
1107                 if(jtom==&(moldyn->atom[0]))
1108                         printf("  total j: %f %f %f\n",jtom->f.x,jtom->f.y,jtom->f.z);
1109                 printf("  energy: %f = %f %f %f %f\n",0.5*f_c*(b*f_a+f_r),
1110                                                     f_c,b,f_a,f_r);
1111                 printf("          %f %f %f\n",zeta_ij,.0,.0);
1112         }
1113 }
1114 #endif
1115
1116         /* dzeta prefactor = - f_c f_a db, (* -0.5 due to force calc) */
1117         pre_dzeta=0.5*f_a*f_c*db;
1118
1119         /* energy contribution */
1120         energy=0.5*f_c*(f_r-b*f_a); // - in albe formalism
1121         pthread_mutex_lock(&emutex);
1122         moldyn->energy+=energy;
1123         pthread_mutex_unlock(&emutex);
1124         pthread_mutex_lock(&(amutex[ai->tag]));
1125         ai->e+=energy;
1126         pthread_mutex_unlock(&(amutex[ai->tag]));
1127
1128         /* reset k counter for second k loop */
1129         kcount=0;
1130
1131
1132                                 /* second loop over atoms k */
1133                                 for(k=0;k<27;k++) {
1134
1135                                         bc_ik=(k<dnlc)?0:1;
1136 #ifdef STATIC_LISTS
1137                                         q=0;
1138
1139                                         while(neighbour_i[k][q]!=-1) {
1140
1141                                                 ktom=&(itom[neighbour_i[k][q]]);
1142                                                 q++;
1143 #elif LOWMEM_LISTS
1144                                         q=neighbour_i[k];
1145
1146                                         while(q!=-1) {
1147
1148                                                 ktom=&(itom[q]);
1149                                                 q=lc->subcell->list[q];
1150 #else
1151                                         that=&(neighbour_i2[k]);
1152                                         list_reset_f(that);
1153
1154                                         if(that->start==NULL)
1155                                                 continue;
1156
1157                                         do {
1158                                                 ktom=that->current->data;
1159 #endif
1160
1161                                                 if(!(ktom->attr&ATOM_ATTR_3BP))
1162                                                         continue;
1163
1164                                                 if(ktom==jtom)
1165                                                         continue;
1166
1167                                                 if(ktom==&(itom[i]))
1168                                                         continue;
1169
1170
1171 /* k2 func here ... */
1172 /* albe 3 body potential function (second k loop) */
1173
1174         if(kcount>ALBE_MAXN)
1175                 printf("FATAL: neighbours!\n");
1176
1177         /* d_ik2 */
1178         d_ik2=exchange->d_ik2[kcount];
1179
1180         if(brand_i==ktom->brand)
1181                 Sk2=params->S2[brand_i];
1182         else
1183                 Sk2=params->S2mixed;
1184
1185         /* return if d_ik > S */
1186         if(d_ik2>Sk2) {
1187                 kcount++;
1188                 continue;
1189         }
1190
1191         /* dist_ik, d_ik */
1192         dist_ik=exchange->dist_ik[kcount];
1193         d_ik=exchange->d_ik[kcount];
1194
1195         /* f_c_ik, df_c_ik */
1196         f_c_ik=exchange->f_c_ik[kcount];
1197         df_c_ik=exchange->df_c_ik[kcount];
1198
1199         /* g, dg, cos_theta */
1200         g=exchange->g[kcount];
1201         dg=exchange->dg[kcount];
1202         cos_theta=exchange->cos_theta[kcount];
1203
1204         /* cos_theta derivatives wrt j,k */
1205         dijdik_inv=1.0/(d_ij*d_ik);
1206         v3_scale(&dcosdrj,&dist_ik,dijdik_inv);         // j
1207         v3_scale(&tmp,&dist_ij,-cos_theta/d_ij2);
1208         v3_add(&dcosdrj,&dcosdrj,&tmp);
1209         v3_scale(&dcosdrk,&dist_ij,dijdik_inv);         // k
1210         v3_scale(&tmp,&dist_ik,-cos_theta/d_ik2);
1211         v3_add(&dcosdrk,&dcosdrk,&tmp);
1212
1213         /* f_c_ik * dg, df_c_ik * g */
1214         fcdg=f_c_ik*dg;
1215         dfcg=df_c_ik*g;
1216
1217         /* derivative wrt j */
1218         v3_scale(&force,&dcosdrj,fcdg*pre_dzeta);
1219
1220         /* force contribution */
1221         pthread_mutex_lock(&(amutex[jtom->tag]));
1222         v3_add(&(jtom->f),&(jtom->f),&force);
1223         pthread_mutex_unlock(&(amutex[jtom->tag]));
1224
1225 #ifdef DEBUG
1226 if(moldyn->time>DSTART&&moldyn->time<DEND) {
1227         if(jtom==&(moldyn->atom[DATOM])) {
1228                 printf("force 3bp (k2): [%d %d %d]\n",ai->tag,jtom->tag,ktom->tag);
1229                 printf("  adding %f %f %f\n",force.x,force.y,force.z);
1230                 printf("  total j: %f %f %f\n",jtom->f.x,jtom->f.y,jtom->f.z);
1231                 printf("  angle: %f\n",acos(cos_theta)*360.0/(2*M_PI));
1232                 printf("    d ij ik = %f %f\n",d_ij,d_ik);
1233         }
1234 }
1235 #endif
1236
1237         /* virial */
1238         pthread_mutex_lock(&(amutex[ai->tag]));
1239         virial_calc(ai,&force,&dist_ij);
1240
1241         /* force contribution to atom i */
1242         v3_scale(&force,&force,-1.0);
1243         v3_add(&(ai->f),&(ai->f),&force);
1244         pthread_mutex_unlock(&(amutex[ai->tag]));
1245
1246         /* derivative wrt k */
1247         v3_scale(&force,&dist_ik,-1.0*dfcg); // dri rik = - drk rik
1248         v3_scale(&tmp,&dcosdrk,fcdg);
1249         v3_add(&force,&force,&tmp);
1250         v3_scale(&force,&force,pre_dzeta);
1251
1252         /* force contribution */
1253         pthread_mutex_lock(&(amutex[ktom->tag]));
1254         v3_add(&(ktom->f),&(ktom->f),&force);
1255         pthread_mutex_unlock(&(amutex[ktom->tag]));
1256
1257 #ifdef DEBUG
1258 if(moldyn->time>DSTART&&moldyn->time<DEND) {
1259         if(ktom==&(moldyn->atom[DATOM])) {
1260                 printf("force 3bp (k2): [%d %d %d]\n",ai->tag,jtom->tag,ktom->tag);
1261                 printf("  adding %f %f %f\n",force.x,force.y,force.z);
1262                 printf("  total k: %f %f %f\n",ktom->f.x,ktom->f.y,ktom->f.z);
1263                 printf("  angle: %f\n",acos(cos_theta)*360.0/(2*M_PI));
1264                 printf("    d ij ik = %f %f\n",d_ij,d_ik);
1265         }
1266 }
1267 #endif
1268
1269         /* virial */
1270         pthread_mutex_lock(&(amutex[ai->tag]));
1271         virial_calc(ai,&force,&dist_ik);
1272
1273         /* force contribution to atom i */
1274         v3_scale(&force,&force,-1.0);
1275         v3_add(&(ai->f),&(ai->f),&force);
1276         pthread_mutex_unlock(&(amutex[ai->tag]));
1277
1278         /* increase k counter */
1279         kcount++;
1280
1281
1282
1283 #ifdef STATIC_LISTS
1284                                         }
1285 #elif LOWMEM_LISTS
1286                                         }
1287 #else
1288                                         } while(list_next_f(that)!=\
1289                                                 L_NO_NEXT_ELEMENT);
1290 #endif
1291
1292                                 }
1293
1294 #ifdef STATIC_LISTS
1295                         }
1296 #elif LOWMEM_LISTS
1297                         }
1298 #else
1299                         } while(list_next_f(this)!=L_NO_NEXT_ELEMENT);
1300 #endif
1301
1302                 }
1303
1304         } // i loop
1305
1306 #ifdef DEBUG
1307         //printf("\n\n");
1308 #endif
1309 #ifdef VDEBUG
1310         printf("\n\n");
1311 #endif
1312
1313 #ifdef DEBUG
1314         //printf("\nATOM 0: %f %f %f\n\n",itom->f.x,itom->f.y,itom->f.z);
1315         if(moldyn->time>DSTART&&moldyn->time<DEND) {
1316                 printf("force:\n");
1317                 printf("  x: %0.40f\n",moldyn->atom[DATOM].f.x);
1318                 printf("  y: %0.40f\n",moldyn->atom[DATOM].f.y);
1319                 printf("  z: %0.40f\n",moldyn->atom[DATOM].f.z);
1320         }
1321 #endif
1322
1323         pthread_exit(NULL);
1324
1325         return 0;
1326 }
1327
1328 int albe_potential_force_calc(t_moldyn *moldyn) {
1329
1330         int i,j,ret;
1331         t_pft_data pft_data[MAX_THREADS];
1332         int count;
1333         pthread_t pft_thread[MAX_THREADS];
1334         t_atom *itom;
1335         t_virial *virial;
1336
1337         count=moldyn->count;
1338         itom=moldyn->atom;
1339
1340         /* reset energy */
1341         moldyn->energy=0.0;
1342
1343         /* reset global virial */
1344         memset(&(moldyn->gvir),0,sizeof(t_virial));
1345
1346         /* reset force, site energy and virial of every atom */
1347         for(i=0;i<count;i++) {
1348
1349                 /* reset force */
1350                 v3_zero(&(itom[i].f));
1351
1352                 /* reset virial */
1353                 virial=&(itom[i].virial);
1354                 virial->xx=0.0;
1355                 virial->yy=0.0;
1356                 virial->zz=0.0;
1357                 virial->xy=0.0;
1358                 virial->xz=0.0;
1359                 virial->yz=0.0;
1360
1361                 /* reset site energy */
1362                 itom[i].e=0.0;
1363
1364         }
1365
1366         /* start threads */
1367         for(j=0;j<MAX_THREADS;j++) {
1368
1369                 /* prepare thread data */
1370                 pft_data[j].moldyn=moldyn;
1371                 pft_data[j].start=j*count/MAX_THREADS;
1372                 if(j==MAX_THREADS-1) {
1373                         pft_data[j].end=count;
1374                 }
1375                 else {
1376                         pft_data[j].end=pft_data[j].start;
1377                         pft_data[j].end+=count/MAX_THREADS;
1378                 }
1379
1380                 ret=pthread_create(&(pft_thread[j]),NULL,
1381                                    potential_force_thread,
1382                                    &(pft_data[j]));
1383                 if(ret)  {
1384                         perror("[albe fast] pf thread create");
1385                         return ret;
1386                 }
1387         }
1388
1389         /* join threads */
1390         for(j=0;j<MAX_THREADS;j++) {
1391
1392                 ret=pthread_join(pft_thread[j],NULL);
1393                 if(ret) {
1394                         perror("[albe fast] pf thread join");
1395                         return ret;
1396                 }
1397         }
1398
1399         /* some postprocessing */
1400         for(i=0;i<count;i++) {
1401                 /* calculate global virial */
1402                 moldyn->gvir.xx+=itom[i].r.x*itom[i].f.x;
1403                 moldyn->gvir.yy+=itom[i].r.y*itom[i].f.y;
1404                 moldyn->gvir.zz+=itom[i].r.z*itom[i].f.z;
1405                 moldyn->gvir.xy+=itom[i].r.y*itom[i].f.x;
1406                 moldyn->gvir.xz+=itom[i].r.z*itom[i].f.x;
1407                 moldyn->gvir.yz+=itom[i].r.z*itom[i].f.y;
1408
1409                 /* check forces regarding the given timestep */
1410                 if(v3_norm(&(itom[i].f))>\
1411                    0.1*moldyn->nnd*itom[i].mass/moldyn->tau_square)
1412                         printf("[moldyn] WARNING: pfc (high force: atom %d)\n",
1413                                i);
1414         }
1415
1416         return 0;
1417 }
1418
1419 #endif // PTHREADS