OpenMM: added combination rule check, disabled restraint check for now as it's buggy

[gromacs/qmmm-gamess-us.git] / src / kernel / genhydro.c

/*
 * 
 *                This source code is part of
 * 
 *                 G   R   O   M   A   C   S
 * 
 *          GROningen MAchine for Chemical Simulations
 * 
 *                        VERSION 3.2.0
 * Written by David van der Spoel, Erik Lindahl, Berk Hess, and others.
 * Copyright (c) 1991-2000, University of Groningen, The Netherlands.
 * Copyright (c) 2001-2004, The GROMACS development team,
 * check out http://www.gromacs.org for more information.

 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 * 
 * If you want to redistribute modifications, please consider that
 * scientific software is very special. Version control is crucial -
 * bugs must be traceable. We will be happy to consider code for
 * inclusion in the official distribution, but derived work must not
 * be called official GROMACS. Details are found in the README & COPYING
 * files - if they are missing, get the official version at www.gromacs.org.
 * 
 * To help us fund GROMACS development, we humbly ask that you cite
 * the papers on the package - you can find them in the top README file.
 * 
 * For more info, check our website at http://www.gromacs.org
 * 
 * And Hey:
 * Gallium Rubidium Oxygen Manganese Argon Carbon Silicon
 */
#ifdef HAVE_CONFIG_H
#include <config.h>
#endif


#include <time.h>
#include <ctype.h>
#include "sysstuff.h"
#include "typedefs.h"
#include "smalloc.h"
#include "copyrite.h"
#include "string2.h"
#include "confio.h"
#include "symtab.h"
#include "vec.h"
#include "statutil.h"
#include "futil.h"
#include "gmx_fatal.h"
#include "physics.h"
#include "calch.h"
#include "genhydro.h"
#include "h_db.h"
#include "ter_db.h"
#include "resall.h"
#include "pgutil.h"
#include "network.h"

static void copy_atom(t_atoms *atoms1,int a1,t_atoms *atoms2,int a2)
{
  atoms2->atom[a2] = atoms1->atom[a1];
  snew(atoms2->atomname[a2],1);
  *atoms2->atomname[a2]=strdup(*atoms1->atomname[a1]);
}

static atom_id pdbasearch_atom(const char *name,int resind,t_atoms *pdba,
                               const char *searchtype,bool bAllowMissing)
{
  int  i;
  
  for(i=0; (i<pdba->nr) && (pdba->atom[i].resind != resind); i++)
    ;
    
  return search_atom(name,i,pdba->nr,pdba->atom,pdba->atomname,
                     searchtype,bAllowMissing);
}

static void hacksearch_atom(int *ii, int *jj, char *name,
                            int nab[], t_hack *ab[], 
                            int resind, t_atoms *pdba)
{
  int  i,j;
  
  *ii=-1;
  if (name[0] == '-') {
    name++;
    resind--;
  }
  for(i=0; (i<pdba->nr) && (pdba->atom[i].resind != resind); i++)
    ;
  for(   ; (i<pdba->nr) && (pdba->atom[i].resind == resind) && (*ii<0); i++)
    for(j=0; (j < nab[i]) && (*ii<0); j++)
      if (ab[i][j].nname && strcmp(name,ab[i][j].nname) == 0) {
        *ii=i;
        *jj=j;
      }
  
  return;
}

void dump_ab(FILE *out,int natom,int nab[], t_hack *ab[], bool bHeader)
{
  int i,j;
  
#define SS(s) (s)?(s):"-"
  /* dump ab */
  if (bHeader)
    fprintf(out,"ADDBLOCK (t_hack) natom=%d\n"
            "%4s %2s %-4s %-4s %2s %-4s %-4s %-4s %-4s %1s %s\n",
            natom,"atom","nr","old","new","tp","ai","aj","ak","al","a","x");
  for(i=0; i<natom; i++)
    for(j=0; j<nab[i]; j++)
      fprintf(out,"%4d %2d %-4s %-4s %2d %-4s %-4s %-4s %-4s %s %g %g %g\n",
              i+1, ab[i][j].nr, SS(ab[i][j].oname), SS(ab[i][j].nname),
              ab[i][j].tp, 
              SS(ab[i][j].AI), SS(ab[i][j].AJ),
              SS(ab[i][j].AK), SS(ab[i][j].AL),
              ab[i][j].atom?"+":"", 
              ab[i][j].newx[XX], ab[i][j].newx[YY], ab[i][j].newx[ZZ]);
#undef SS
}

static t_hackblock *get_hackblocks(t_atoms *pdba, int nah, t_hackblock ah[],
                                   int nterpairs,
                                   t_hackblock **ntdb, t_hackblock **ctdb, 
                                   int *rN, int *rC)
{
  int i,rnr;
  t_hackblock *hb,*ahptr;

  /* make space */
  snew(hb,pdba->nres);
  /* first the termini */
  for(i=0; i<nterpairs; i++) {
    if (ntdb[i] != NULL) {
      copy_t_hackblock(ntdb[i], &hb[rN[i]]);
    }
    if (ctdb[i] != NULL) {
      merge_t_hackblock(ctdb[i], &hb[rC[i]]);
    }
  }
  /* then the whole hdb */
  for(rnr=0; rnr < pdba->nres; rnr++) {
    ahptr=search_h_db(nah,ah,*pdba->resinfo[rnr].rtp);
    if ( ahptr ) {
      if (hb[rnr].name==NULL)
        hb[rnr].name=strdup(ahptr->name);
      merge_hacks(ahptr, &hb[rnr]);
    }
  }
  return hb;
}

static const char Hnum[] = "123456";

static void expand_hackblocks_one(t_hackblock *hbr, char *atomname, 
                                  int *nabi, t_hack **abi, bool bN, bool bC)
{
  int j, k, l, d;
  bool bIgnore;
  
  /* we'll recursively add atoms to atoms */
  for(j=0; j < hbr->nhack; j++) {
    /* first check if we're in the N- or C-terminus, then we should ignore 
       all hacks involving atoms from resp. previous or next residue
       (i.e. which name begins with '-' (N) or '+' (C) */
    bIgnore = FALSE;
    if ( bN ) /* N-terminus: ignore '-' */
      for(k=0; k<4 && hbr->hack[j].a[k] && !bIgnore; k++)
        bIgnore = hbr->hack[j].a[k][0]=='-';
    if ( bC ) /* C-terminus: ignore '+' */
      for(k=0; k<4 && hbr->hack[j].a[k] && !bIgnore; k++)
        bIgnore = hbr->hack[j].a[k][0]=='+';
    /* must be either hdb entry (tp>0) or add from tdb (oname==NULL)
       and first control aton (AI) matches this atom or
       delete/replace from tdb (oname!=NULL) and oname matches this atom */
    if (debug) fprintf(debug," %s",
                       hbr->hack[j].oname?hbr->hack[j].oname:hbr->hack[j].AI);

    if ( !bIgnore &&
         ( ( ( hbr->hack[j].tp > 0 || hbr->hack[j].oname==NULL ) &&
             strcmp(atomname, hbr->hack[j].AI) == 0 ) ||
           ( hbr->hack[j].oname!=NULL &&
             strcmp(atomname, hbr->hack[j].oname) == 0) ) ) {
      /* now expand all hacks for this atom */
      if (debug) fprintf(debug," +%dh",hbr->hack[j].nr);
      srenew(*abi,*nabi + hbr->hack[j].nr);
      for(k=0; k < hbr->hack[j].nr; k++) {
        copy_t_hack(&hbr->hack[j], &(*abi)[*nabi + k]);
        (*abi)[*nabi + k].bXSet = FALSE;
        /* if we're adding (oname==NULL) and don't have a new name (nname) 
           yet, build it from atomname */
        if ( (*abi)[*nabi + k].nname==NULL ) {
          if ( (*abi)[*nabi + k].oname==NULL ) {
            (*abi)[*nabi + k].nname=strdup(atomname);
            (*abi)[*nabi + k].nname[0]='H';
          }
        } else {
          if (gmx_debug_at) {
            fprintf(debug,"Hack '%s' %d, replacing nname '%s' with '%s' (old name '%s')\n",
                    atomname,j,
                    (*abi)[*nabi + k].nname,hbr->hack[j].nname,
                    (*abi)[*nabi + k].oname ? (*abi)[*nabi + k].oname : "");
          }
          sfree((*abi)[*nabi + k].nname);
          (*abi)[*nabi + k].nname=strdup(hbr->hack[j].nname);
        }
        /* if adding more than one atom, number them */
        if ( hbr->hack[j].nr > 1 ) {
          l = strlen((*abi)[*nabi + k].nname);
          srenew((*abi)[*nabi + k].nname, l+2);
          (*abi)[*nabi + k].nname[l] = Hnum[k]; /* 1, 2, 3 .... */
          (*abi)[*nabi + k].nname[l+1] = '\0';
        }
      }
      (*nabi) += hbr->hack[j].nr;
      
      /* add hacks to atoms we've just added */
      if ( hbr->hack[j].tp > 0 || hbr->hack[j].oname==NULL )
        for(k=0; k < hbr->hack[j].nr; k++)
          expand_hackblocks_one(hbr, (*abi)[*nabi-hbr->hack[j].nr+k].nname, 
                                nabi, abi, bN, bC);
    }
  }
}

static void expand_hackblocks(t_atoms *pdba, t_hackblock hb[], 
                              int nab[], t_hack *ab[], 
                              int nterpairs, int *rN, int *rC)
{
  int i,j;
  bool bN,bC;
  
  for(i=0; i < pdba->nr; i++) {
    bN = FALSE;
    for(j=0; j<nterpairs && !bN; j++)
      bN = pdba->atom[i].resind==rN[j];
    bC = FALSE;
    for(j=0; j<nterpairs && !bC; j++)
      bC = pdba->atom[i].resind==rC[j];

    /* add hacks to this atom */
    expand_hackblocks_one(&hb[pdba->atom[i].resind], *pdba->atomname[i], 
                          &nab[i], &ab[i], bN, bC);
  }
  if (debug) fprintf(debug,"\n");
}

static int check_atoms_present(t_atoms *pdba, int nab[], t_hack *ab[])
{
  int i, j, k, d, rnr, nadd;
  
  nadd=0;
  for(i=0; i < pdba->nr; i++) {
    rnr = pdba->atom[i].resind;
    for(j=0; j<nab[i]; j++) {
      if ( ab[i][j].oname==NULL ) { 
        /* we're adding */
        if (ab[i][j].nname == NULL)
          gmx_incons("ab[i][j].nname not allocated");
        /* check if the atom is already present */
        k = pdbasearch_atom(ab[i][j].nname, rnr, pdba, "check", TRUE);
        if ( k != -1 ) {
          /* We found the added atom. */
          ab[i][j].bAlreadyPresent = TRUE;
          if (debug) {
            fprintf(debug,"Atom '%s' in residue '%s' %d is already present\n",
                    ab[i][j].nname,
                    *pdba->resinfo[rnr].name,pdba->resinfo[rnr].nr);
          }
        } else {
          ab[i][j].bAlreadyPresent = FALSE;
          /* count how many atoms we'll add */
          nadd++;
        }
      } else if ( ab[i][j].nname==NULL ) {
        /* we're deleting */
        nadd--;
      }
    }
  }
  
  return nadd;
}

static void calc_all_pos(t_atoms *pdba, rvec x[], int nab[], t_hack *ab[],
                         bool bCheckMissing)
{
  int i, j, ii, jj, m, ia, d, rnr,l=0;
#define MAXH 4
  rvec xa[4];     /* control atoms for calc_h_pos */
  rvec xh[MAXH]; /* hydrogen positions from calc_h_pos */
  bool bFoundAll;

  jj = 0;
  
  for(i=0; i < pdba->nr; i++) {
    rnr   = pdba->atom[i].resind;
    for(j=0; j < nab[i]; j+=ab[i][j].nr) {
      /* check if we're adding: */
      if (ab[i][j].oname==NULL && ab[i][j].tp > 0) {
        bFoundAll = TRUE;
        for(m=0; (m<ab[i][j].nctl && bFoundAll); m++) {
          ia = pdbasearch_atom(ab[i][j].a[m], rnr, pdba,
                               bCheckMissing ? "atom" : "check",
                               !bCheckMissing);
          if (ia < 0) {
            /* not found in original atoms, might still be in t_hack (ab) */
            hacksearch_atom(&ii, &jj, ab[i][j].a[m], nab, ab, rnr, pdba);
            if (ii >= 0) {
              copy_rvec(ab[ii][jj].newx, xa[m]);
            } else {
              bFoundAll = FALSE;
              if (bCheckMissing) {
                gmx_fatal(FARGS,"Atom %s not found in residue %s %d"
                          ", rtp entry %s"
                          " while adding hydrogens",
                          ab[i][j].a[m],
                          *pdba->resinfo[rnr].name,
                          pdba->resinfo[rnr].nr,
                          *pdba->resinfo[rnr].rtp);
              }
            }
          } else
            copy_rvec(x[ia], xa[m]);
        }
        if (bFoundAll) {
          for(m=0; (m<MAXH); m++)
            for(d=0; d<DIM; d++)
              if (m<ab[i][j].nr)
                xh[m][d] = 0;
              else
                xh[m][d] = NOTSET;
          calc_h_pos(ab[i][j].tp, xa, xh, &l);
          for(m=0; m<ab[i][j].nr; m++) {
            copy_rvec(xh[m],ab[i][j+m].newx);
            ab[i][j+m].bXSet = TRUE;
          }
        }
      }
    }
  }
}

static void free_ab(int natoms,int *nab,t_hack **ab)
{
  int i;

  for(i=0; i<natoms; i++) {
    free_t_hack(nab[i], &ab[i]);
  }
  sfree(nab);
  sfree(ab);
}

static int add_h_low(t_atoms **pdbaptr, rvec *xptr[], 
                     int nah, t_hackblock ah[],
                     int nterpairs, t_hackblock **ntdb, t_hackblock **ctdb, 
                     int *rN, int *rC, bool bCheckMissing,
                     int **nabptr, t_hack ***abptr,
                     bool bUpdate_pdba, bool bKeep_old_pdba)
{
  t_atoms     *newpdba=NULL,*pdba=NULL;
  int         nadd;
  int         i,newi,j,d,natoms,nalreadypresent;
  int         *nab=NULL;
  t_hack      **ab=NULL;
  t_hackblock *hb;
  rvec        *xn;
  bool        bKeep_ab;
  
  /* set flags for adding hydrogens (according to hdb) */
  pdba=*pdbaptr;
  natoms=pdba->nr;
  
  if (nabptr && abptr) {
    /* the first time these will be pointers to NULL, but we will
       return in them the completed arrays, which we will get back
       the second time */
    nab = *nabptr;
    ab  = *abptr;
    bKeep_ab=TRUE;
    if (debug) fprintf(debug,"pointer to ab found\n");
  } else {
    bKeep_ab=FALSE;
  }
  
  if (nab && ab) {
    /* WOW, everything was already figured out */
    bUpdate_pdba = FALSE;
    if (debug) fprintf(debug,"pointer to non-null ab found\n");
  } else {
    /* We'll have to do all the hard work */
    bUpdate_pdba = TRUE;
    /* first get all the hackblocks for each residue: */
    hb = get_hackblocks(pdba, nah, ah, nterpairs, ntdb, ctdb, rN, rC);
    if (debug) dump_hb(debug, pdba->nres, hb);
    
    /* expand the hackblocks to atom level */
    snew(nab,natoms);
    snew(ab,natoms);
    expand_hackblocks(pdba, hb, nab, ab, nterpairs, rN, rC);
    free_t_hackblock(pdba->nres, &hb);
  }
  
  if (debug) { 
    fprintf(debug,"before calc_all_pos\n");
    dump_ab(debug, natoms, nab, ab, TRUE);
  }
  
  /* Now calc the positions */
  calc_all_pos(pdba, *xptr, nab, ab, bCheckMissing);

  if (debug) { 
    fprintf(debug,"after calc_all_pos\n");
    dump_ab(debug, natoms, nab, ab, TRUE);
  }
  
  if (bUpdate_pdba) {
    /* we don't have to add atoms that are already present in pdba,
       so we will remove them from the ab (t_hack) */
    nadd = check_atoms_present(pdba, nab, ab);
    if (debug) {
      fprintf(debug, "removed add hacks that were already in pdba:\n");
      dump_ab(debug, natoms, nab, ab, TRUE);
      fprintf(debug, "will be adding %d atoms\n",nadd);
    }
    
    /* Copy old atoms, making space for new ones */
    snew(newpdba,1);
    init_t_atoms(newpdba,natoms+nadd,FALSE);
    newpdba->nres    = pdba->nres;   
    sfree(newpdba->resinfo);
    newpdba->resinfo = pdba->resinfo;
  } else {
    nadd = 0;
  }
  if (debug) fprintf(debug,"snew xn for %d old + %d new atoms %d total)\n",
                     natoms, nadd, natoms+nadd);

  if (nadd == 0) {
    /* There is nothing to do: return now */
    if (!bKeep_ab) {
      free_ab(natoms,nab,ab);
    }

    return natoms;
  }

  snew(xn,natoms+nadd);
  newi=0;
  for(i=0; (i<natoms); i++) {
    /* check if this atom wasn't scheduled for deletion */
    if ( nab[i]==0 || (ab[i][0].nname != NULL) ) {
      if (newi >= natoms+nadd) {
        /*gmx_fatal(FARGS,"Not enough space for adding atoms");*/
        nadd+=10;
        srenew(xn,natoms+nadd);
        if (bUpdate_pdba) {
          srenew(newpdba->atom,natoms+nadd);
          srenew(newpdba->atomname,natoms+nadd);
        }
        debug_gmx();
      }
      if (debug) fprintf(debug,"(%3d) %3d %4s %4s%3d %3d",
                         i+1, newi+1, *pdba->atomname[i],
                         *pdba->resinfo[pdba->atom[i].resind].name,
                         pdba->resinfo[pdba->atom[i].resind].nr, nab[i]);
      if (bUpdate_pdba)
        copy_atom(pdba,i, newpdba,newi);
      copy_rvec((*xptr)[i],xn[newi]);
      /* process the hacks for this atom */
      nalreadypresent = 0;
      for(j=0; j<nab[i]; j++) {
        if ( ab[i][j].oname==NULL ) { /* add */
          newi++;
          if (newi >= natoms+nadd) {
            /* gmx_fatal(FARGS,"Not enough space for adding atoms");*/
            nadd+=10;
            srenew(xn,natoms+nadd);
            if (bUpdate_pdba) {
              srenew(newpdba->atom,natoms+nadd);
              srenew(newpdba->atomname,natoms+nadd);
            }
            debug_gmx();
          }
          if (bUpdate_pdba) {
            newpdba->atom[newi].resind=pdba->atom[i].resind;
          }
          if (debug) fprintf(debug," + %d",newi+1);
        }
        if (ab[i][j].nname != NULL &&
            (ab[i][j].oname == NULL ||
             strcmp(ab[i][j].oname,*newpdba->atomname[newi]) == 0)) {
          /* add or replace */
          if (ab[i][j].oname == NULL && ab[i][j].bAlreadyPresent) {
            /* This atom is already present, copy it from the input. */
            nalreadypresent++;
            if (bUpdate_pdba) {
              copy_atom(pdba,i+nalreadypresent, newpdba,newi);
            }
            copy_rvec((*xptr)[i+nalreadypresent],xn[newi]);
          } else {
          if (bUpdate_pdba) {
            if (gmx_debug_at) {
              fprintf(debug,"Replacing %d '%s' with (old name '%s') %s\n",
                      newi,
                      (newpdba->atomname[newi] && *newpdba->atomname[newi]) ? *newpdba->atomname[newi] : "",
                      ab[i][j].oname ? ab[i][j].oname : "",
                      ab[i][j].nname);
            }
            snew(newpdba->atomname[newi],1);
            *newpdba->atomname[newi]=strdup(ab[i][j].nname);
            if ( ab[i][j].oname!=NULL && ab[i][j].atom ) { /* replace */
/*            newpdba->atom[newi].m    = ab[i][j].atom->m; */
/*            newpdba->atom[newi].q    = ab[i][j].atom->q; */
/*            newpdba->atom[newi].type = ab[i][j].atom->type; */
            }
          }
          if (ab[i][j].bXSet)
            copy_rvec(ab[i][j].newx, xn[newi]);
          }
          if (bUpdate_pdba && debug) 
            fprintf(debug," %s %g %g",*newpdba->atomname[newi],
                    newpdba->atom[newi].m,newpdba->atom[newi].q);
        }
      }
      newi++;
      i += nalreadypresent;
      if (debug) fprintf(debug,"\n");
    }
  }
  if (bUpdate_pdba)
    newpdba->nr = newi;
  
  if ( bKeep_ab ) {
    *nabptr=nab;
    *abptr=ab;
  } else {
    /* Clean up */
    free_ab(natoms,nab,ab);
  }
    
  if ( bUpdate_pdba ) {
    if ( !bKeep_old_pdba ) {
      for(i=0; i < natoms; i++) {
        /* Do not free the atomname string itself, it might be in symtab */
        /* sfree(*(pdba->atomname[i])); */
        /* sfree(pdba->atomname[i]); */
      }
      sfree(pdba->atomname);
      sfree(pdba->atom);
      sfree(pdba->pdbinfo);
      sfree(pdba);
    }
    *pdbaptr=newpdba;
  } else
    nadd = newi-natoms;
  
  sfree(*xptr);
  *xptr=xn;
  
  return newi;
}

void deprotonate(t_atoms *atoms,rvec *x)
{
  int  i,j;
  
  j=0;
  for(i=0; i<atoms->nr; i++) {
    if ( (*atoms->atomname[i])[0] != 'H' ) {
      atoms->atomname[j]=atoms->atomname[i];
      atoms->atom[j]=atoms->atom[i];
      copy_rvec(x[i],x[j]);
      j++;
    }
  }
  atoms->nr=j;
}

int add_h(t_atoms **pdbaptr, rvec *xptr[], 
          int nah, t_hackblock ah[],
          int nterpairs, t_hackblock **ntdb, t_hackblock **ctdb, 
          int *rN, int *rC, bool bAllowMissing,
          int **nabptr, t_hack ***abptr,
          bool bUpdate_pdba, bool bKeep_old_pdba)
{
  int nold,nnew,niter;

  /* Here we loop to be able to add atoms to added atoms.
   * We should not check for missing atoms here.
   */
  niter = 0;
  nnew = 0;
  do {
    nold = nnew;
    nnew = add_h_low(pdbaptr,xptr,nah,ah,nterpairs,ntdb,ctdb,rN,rC,FALSE,
                     nabptr,abptr,bUpdate_pdba,bKeep_old_pdba);
    niter++;
    if (niter > 100) {
      gmx_fatal(FARGS,"More than 100 iterations of add_h. Maybe you are trying to replace an added atom (this is not supported)?");
    }
  } while (nnew > nold);
  
  if (!bAllowMissing) {
    /* Call add_h_low once more, now only for the missing atoms check */
    add_h_low(pdbaptr,xptr,nah,ah,nterpairs,ntdb,ctdb,rN,rC,TRUE,
              nabptr,abptr,bUpdate_pdba,bKeep_old_pdba);
  }

  return nnew;
}

int protonate(t_atoms **atomsptr,rvec **xptr,t_protonate *protdata)
{
#define NTERPAIRS 1
  t_atoms *atoms;
  bool    bUpdate_pdba,bKeep_old_pdba;
  int     nntdb,nctdb,nt,ct;
  int     nadd;
  
  atoms=NULL;
  if ( !protdata->bInit ) {
    if (debug) fprintf(debug,"protonate: Initializing protdata\n");
    /* set forcefield to use: */
    strcpy(protdata->FF,"ffgmx2");
    /* get the databases: */
    protdata->nah=read_h_db(protdata->FF,&protdata->ah);
    open_symtab(&protdata->tab); 
    protdata->atype=read_atype(protdata->FF,&protdata->tab);
    nntdb = read_ter_db(protdata->FF,'n',&protdata->ntdb,protdata->atype);
    if (nntdb < 1)
      gmx_fatal(FARGS,"no n-terminus db");
    nctdb = read_ter_db(protdata->FF,'c',&protdata->ctdb,protdata->atype);
    if (nctdb < 1)
      gmx_fatal(FARGS,"no c-terminus db");
    
    /* set terminus types: -NH3+ (different for Proline) and -COO- */
    atoms=*atomsptr;
    snew(protdata->sel_ntdb, NTERPAIRS);
    snew(protdata->sel_ctdb, NTERPAIRS);

    if (nntdb>=4 && nctdb>=2) {
      /* Yuk, yuk, hardcoded default termini selections !!! */
      if (strncmp(*atoms->resinfo[atoms->atom[atoms->nr-1].resind].name,"PRO",3)==0)
        nt = 3;
      else
        nt = 1;
      ct = 1;
    } else {
      nt = 0;
      ct = 0;
    }
    protdata->sel_ntdb[0]=&(protdata->ntdb[nt]);
    protdata->sel_ctdb[0]=&(protdata->ctdb[ct]);
  
    /* set terminal residue numbers: */
    snew(protdata->rN, NTERPAIRS);
    snew(protdata->rC, NTERPAIRS);
    protdata->rN[0]=0;
    protdata->rC[0]=atoms->atom[atoms->nr-1].resind;
    
    /* keep unprotonated topology: */
    protdata->upatoms = atoms;
    /* we don't have these yet: */
    protdata->patoms = NULL;
    bUpdate_pdba=TRUE;
    bKeep_old_pdba=TRUE;
    
    /* clear hackblocks: */
    protdata->nab=NULL;
    protdata->ab=NULL;
    
    /* set flag to show we're initialized: */
    protdata->bInit=TRUE;
  } else {
    if (debug) fprintf(debug,"protonate: using available protdata\n");
    /* add_h will need the unprotonated topoloy again: */
    atoms = protdata->upatoms;
    bUpdate_pdba=FALSE;
    bKeep_old_pdba=FALSE;
  }
  
  /* now protonate */
  nadd = add_h(&atoms, xptr, protdata->nah, protdata->ah,
               NTERPAIRS, protdata->sel_ntdb, protdata->sel_ctdb,
               protdata->rN, protdata->rC, TRUE,
               &protdata->nab, &protdata->ab, bUpdate_pdba, bKeep_old_pdba);
  if ( ! protdata->patoms )
    /* store protonated topology */
    protdata->patoms = atoms;
  *atomsptr = protdata->patoms;
  if (debug) fprintf(debug,"natoms: %d -> %d (nadd=%d)\n",
                     protdata->upatoms->nr, protdata->patoms->nr, nadd);
  return nadd;
#undef NTERPAIRS  
}