src/gmxlib/dihres.c

   1 /*
   2  *
   3  *                This source code is part of
   4  *
   5  *                 G   R   O   M   A   C   S
   6  *
   7  *          GROningen MAchine for Chemical Simulations
   8  *
   9  *                        VERSION 3.2.0
  10  * Written by David van der Spoel, Erik Lindahl, Berk Hess, and others.
  11  * Copyright (c) 1991-2000, University of Groningen, The Netherlands.
  12  * Copyright (c) 2001-2004, The GROMACS development team,
  13  * check out http://www.gromacs.org for more information.
  14
  15  * This program is free software; you can redistribute it and/or
  16  * modify it under the terms of the GNU General Public License
  17  * as published by the Free Software Foundation; either version 2
  18  * of the License, or (at your option) any later version.
  19  *
  20  * If you want to redistribute modifications, please consider that
  21  * scientific software is very special. Version control is crucial -
  22  * bugs must be traceable. We will be happy to consider code for
  23  * inclusion in the official distribution, but derived work must not
  24  * be called official GROMACS. Details are found in the README & COPYING
  25  * files - if they are missing, get the official version at www.gromacs.org.
  26  *
  27  * To help us fund GROMACS development, we humbly ask that you cite
  28  * the papers on the package - you can find them in the top README file.
  29  *
  30  * For more info, check our website at http://www.gromacs.org
  31  *
  32  * And Hey:
  33  * GROningen Mixture of Alchemy and Childrens' Stories
  34  */
  35 #ifdef HAVE_CONFIG_H
  36 #include <config.h>
  37 #endif
  38
  39 #include <math.h>
  40 #include "typedefs.h"
  41 #include "sysstuff.h"
  42 #include "smalloc.h"
  43 #include "macros.h"
  44 #include "physics.h"
  45 #include "vec.h"
  46 #include "futil.h"
  47 #include "xvgr.h"
  48 #include "gmx_fatal.h"
  49 #include "bondf.h"
  50 #include "copyrite.h"
  51 #include "disre.h"
  52 #include "main.h"
  53 #include "mtop_util.h"
  54 #include "dihre.h"
  55
  56 void init_dihres(FILE *fplog,gmx_mtop_t *mtop,t_inputrec *ir,t_fcdata *fcd)
  57 {
  58   int count;
  59
  60   fcd->dihre_fc = ir->dihre_fc;
  61
  62   count = gmx_mtop_ftype_count(mtop,F_DIHRES);
  63
  64   if (fplog && count) {
  65     fprintf(fplog,"There are %d dihedral restraints\n",count);
  66   }
  67 }
  68
  69 real ta_dihres(int nfa,const t_iatom forceatoms[],const t_iparams ip[],
  70                const rvec x[],rvec f[],rvec fshift[],
  71                const t_pbc *pbc,const t_graph *g,
  72                real lambda,real *dvdlambda,
  73                const t_mdatoms *md,t_fcdata *fcd,
  74                int *ddgatindex)
  75 {
  76   real vtot = 0;
  77   int  ai,aj,ak,al,i,k,type,typep,label,power,t1,t2,t3;
  78   real phi0,phi,ddphi,ddp,dp,dp2,dphi,kfac,sign,d2r,fc;
  79   rvec r_ij,r_kj,r_kl,m,n;
  80
  81   fc  = fcd->dihre_fc;
  82   d2r = DEG2RAD;
  83   k   = 0;
  84   for(i=0; (i<nfa); ) {
  85     type = forceatoms[i++];
  86     ai   = forceatoms[i++];
  87     aj   = forceatoms[i++];
  88     ak   = forceatoms[i++];
  89     al   = forceatoms[i++];
  90
  91     phi0  = ip[type].dihres.phi*d2r;
  92     dphi  = ip[type].dihres.dphi*d2r;
  93     kfac  = ip[type].dihres.kfac*fc;
  94     power = ip[type].dihres.power;
  95     label = ip[type].dihres.label;
  96
  97     phi = dih_angle(x[ai],x[aj],x[ak],x[al],pbc,r_ij,r_kj,r_kl,m,n,
  98                     &sign,&t1,&t2,&t3);
  99     /* 84 flops */
 100
 101     if (debug)
 102         fprintf(debug,"dihres[%d]: %d %d %d %d : phi=%f, dphi=%f, kfac=%f, power=%d, label=%d\n",
 103                 k++,ai,aj,ak,al,phi,dphi,kfac,power,label);
 104
 105     /* phi can jump if phi0 is close to Pi/-Pi, which will cause huge
 106      * force changes if we just apply a normal harmonic.
 107      * Instead, we first calculate phi-phi0 and take it modulo (-Pi,Pi).
 108      * This means we will never have the periodicity problem, unless
 109      * the dihedral is Pi away from phiO, which is very unlikely due to
 110      * the potential.
 111      */
 112     dp = phi-phi0;
 113     if (fabs(dp) > dphi) {
 114       /* dp cannot be outside (-2*pi,2*pi) */
 115       if (dp >= M_PI)
 116         dp -= 2*M_PI;
 117       else if(dp < -M_PI)
 118         dp += 2*M_PI;
 119
 120       if (dp > dphi)
 121         ddp = dp-dphi;
 122       else if (dp < -dphi)
 123         ddp = dp+dphi;
 124       else
 125         ddp = 0;
 126
 127       if (ddp != 0.0) {
 128         vtot += 0.5*kfac*ddp*ddp;
 129         ddphi = kfac*ddp;
 130
 131         do_dih_fup(ai,aj,ak,al,ddphi,r_ij,r_kj,r_kl,m,n,
 132                    f,fshift,pbc,g,x,t1,t2,t3);          /* 112          */
 133       }
 134     }
 135   }
 136   return vtot;
 137 }