OOPSE-1.0/libmdtools/Thermo.cpp

#include <math.h>
#include <iostream>
using namespace std;

#ifdef IS_MPI
#include <mpi.h>
#endif //is_mpi

#include "Thermo.hpp"
#include "SRI.hpp"
#include "Integrator.hpp"
#include "simError.h"
#include "MatVec3.h"

#ifdef IS_MPI
#define __C
#include "mpiSimulation.hpp"
#endif // is_mpi

inline double roundMe( double x ){
          return ( x >= 0 ) ? floor( x + 0.5 ) : ceil( x - 0.5 );
}

Thermo::Thermo( SimInfo* the_info ) { 
  info = the_info;
  int baseSeed = the_info->getSeed();
  
  gaussStream = new gaussianSPRNG( baseSeed );
}

Thermo::~Thermo(){
  delete gaussStream;
}

double Thermo::getKinetic(){

  const double e_convert = 4.184E-4; // convert kcal/mol -> (amu A^2)/fs^2
  double kinetic;
  double amass;
  double aVel[3], aJ[3], I[3][3];
  int i, j, k, kl;

  double kinetic_global;
  vector<StuntDouble *> integrableObjects = info->integrableObjects;
  
  kinetic = 0.0;
  kinetic_global = 0.0;

  for (kl=0; kl<integrableObjects.size(); kl++) {
    integrableObjects[kl]->getVel(aVel);
    amass = integrableObjects[kl]->getMass();

   for(j=0; j<3; j++) 
      kinetic += amass*aVel[j]*aVel[j];

   if (integrableObjects[kl]->isDirectional()){
 
      integrableObjects[kl]->getJ( aJ );
      integrableObjects[kl]->getI( I );

      if (integrableObjects[kl]->isLinear()) {
        i = integrableObjects[kl]->linearAxis();
        j = (i+1)%3;
        k = (i+2)%3;
        kinetic += aJ[j]*aJ[j]/I[j][j] + aJ[k]*aJ[k]/I[k][k];
      } else {
        for (j=0; j<3; j++) 
          kinetic += aJ[j]*aJ[j] / I[j][j];
      }
   }
  }
#ifdef IS_MPI
  MPI_Allreduce(&kinetic,&kinetic_global,1,MPI_DOUBLE,
                MPI_SUM, MPI_COMM_WORLD);
  kinetic = kinetic_global;
#endif //is_mpi
  
  kinetic = kinetic * 0.5 / e_convert;

  return kinetic;
}

double Thermo::getPotential(){
  
  double potential_local;
  double potential;
  int el, nSRI;
  Molecule* molecules;

  molecules = info->molecules;
  nSRI = info->n_SRI;

  potential_local = 0.0;
  potential = 0.0;
  potential_local += info->lrPot;

  for( el=0; el<info->n_mol; el++ ){    
    potential_local += molecules[el].getPotential();
  }

  // Get total potential for entire system from MPI.
#ifdef IS_MPI
  MPI_Allreduce(&potential_local,&potential,1,MPI_DOUBLE,
                MPI_SUM, MPI_COMM_WORLD);
#else
  potential = potential_local; 
#endif // is_mpi

  return potential;
}

double Thermo::getTotalE(){

  double total;

  total = this->getKinetic() + this->getPotential();
  return total;
}

double Thermo::getTemperature(){

  const double kb = 1.9872156E-3; // boltzman's constant in kcal/(mol K)
  double temperature;

  temperature = ( 2.0 * this->getKinetic() ) / ((double)info->ndf * kb );
  return temperature;
}

double Thermo::getVolume() {

  return info->boxVol;
}

double Thermo::getPressure() {

  // Relies on the calculation of the full molecular pressure tensor
  
  const double p_convert = 1.63882576e8;
  double press[3][3];
  double pressure;

  this->getPressureTensor(press);

  pressure = p_convert * (press[0][0] + press[1][1] + press[2][2]) / 3.0;

  return pressure;
}

double Thermo::getPressureX() {

  // Relies on the calculation of the full molecular pressure tensor
  
  const double p_convert = 1.63882576e8;
  double press[3][3];
  double pressureX;

  this->getPressureTensor(press);

  pressureX = p_convert * press[0][0];

  return pressureX;
}

double Thermo::getPressureY() {

  // Relies on the calculation of the full molecular pressure tensor
  
  const double p_convert = 1.63882576e8;
  double press[3][3];
  double pressureY;

  this->getPressureTensor(press);

  pressureY = p_convert * press[1][1];

  return pressureY;
}

double Thermo::getPressureZ() {

  // Relies on the calculation of the full molecular pressure tensor
  
  const double p_convert = 1.63882576e8;
  double press[3][3];
  double pressureZ;

  this->getPressureTensor(press);

  pressureZ = p_convert * press[2][2];

  return pressureZ;
}


void Thermo::getPressureTensor(double press[3][3]){
  // returns pressure tensor in units amu*fs^-2*Ang^-1
  // routine derived via viral theorem description in:
  // Paci, E. and Marchi, M. J.Phys.Chem. 1996, 100, 4314-4322

  const double e_convert = 4.184e-4;

  double molmass, volume;
  double vcom[3];
  double p_local[9], p_global[9];
  int i, j, k;

  for (i=0; i < 9; i++) {    
    p_local[i] = 0.0;
    p_global[i] = 0.0;
  }

  // use velocities of integrableObjects and their masses:  

  for (i=0; i < info->integrableObjects.size(); i++) {

    molmass = info->integrableObjects[i]->getMass();
    
    info->integrableObjects[i]->getVel(vcom);
    
    p_local[0] += molmass * (vcom[0] * vcom[0]); 
    p_local[1] += molmass * (vcom[0] * vcom[1]); 
    p_local[2] += molmass * (vcom[0] * vcom[2]); 
    p_local[3] += molmass * (vcom[1] * vcom[0]); 
    p_local[4] += molmass * (vcom[1] * vcom[1]); 
    p_local[5] += molmass * (vcom[1] * vcom[2]); 
    p_local[6] += molmass * (vcom[2] * vcom[0]); 
    p_local[7] += molmass * (vcom[2] * vcom[1]); 
    p_local[8] += molmass * (vcom[2] * vcom[2]); 

  }

  // Get total for entire system from MPI.
  
#ifdef IS_MPI
  MPI_Allreduce(p_local,p_global,9,MPI_DOUBLE, MPI_SUM, MPI_COMM_WORLD);
#else
  for (i=0; i<9; i++) {
    p_global[i] = p_local[i]; 
  }
#endif // is_mpi

  volume = this->getVolume();


  for(i = 0; i < 3; i++) {
    for (j = 0; j < 3; j++) {
      k = 3*i + j;
      press[i][j] = (p_global[k] + info->tau[k]*e_convert) / volume;
    }
  }
}

void Thermo::velocitize() {
  
  double aVel[3], aJ[3], I[3][3];
  int i, j, l, m, n, vr, vd; // velocity randomizer loop counters
  double vdrift[3];
  double vbar;
  const double kb = 8.31451e-7; // kb in amu, angstroms, fs, etc.
  double av2;
  double kebar;
  double temperature;
  int nobj;

  nobj = info->integrableObjects.size();
  
  temperature   = info->target_temp;
  
  kebar = kb * temperature * (double)info->ndfRaw / 
    ( 2.0 * (double)info->ndf );
  
  for(vr = 0; vr < nobj; vr++){
    
    // uses equipartition theory to solve for vbar in angstrom/fs

    av2 = 2.0 * kebar / info->integrableObjects[vr]->getMass();
    vbar = sqrt( av2 );

    // picks random velocities from a gaussian distribution
    // centered on vbar

    for (j=0; j<3; j++) 
      aVel[j] = vbar * gaussStream->getGaussian();
    
    info->integrableObjects[vr]->setVel( aVel );
    
    if(info->integrableObjects[vr]->isDirectional()){

      info->integrableObjects[vr]->getI( I );

      if (info->integrableObjects[vr]->isLinear()) {

        l= info->integrableObjects[vr]->linearAxis();
        m = (l+1)%3;
        n = (l+2)%3;

        aJ[l] = 0.0;
        vbar = sqrt( 2.0 * kebar * I[m][m] );
        aJ[m] = vbar * gaussStream->getGaussian();
        vbar = sqrt( 2.0 * kebar * I[n][n] );
        aJ[n] = vbar * gaussStream->getGaussian();
        
      } else {
        for (j = 0 ; j < 3; j++) {
          vbar = sqrt( 2.0 * kebar * I[j][j] );
          aJ[j] = vbar * gaussStream->getGaussian();
        }       
      } // else isLinear

      info->integrableObjects[vr]->setJ( aJ ); 
      
    }//isDirectional 

  }

  // Get the Center of Mass drift velocity.

  getCOMVel(vdrift);
  
  //  Corrects for the center of mass drift.
  // sums all the momentum and divides by total mass.

  for(vd = 0; vd < nobj; vd++){
    
    info->integrableObjects[vd]->getVel(aVel);
    
    for (j=0; j < 3; j++) 
      aVel[j] -= vdrift[j];
        
    info->integrableObjects[vd]->setVel( aVel );
  }

}

void Thermo::getCOMVel(double vdrift[3]){

  double mtot, mtot_local;
  double aVel[3], amass;
  double vdrift_local[3];
  int vd, j;
  int nobj;

  nobj   = info->integrableObjects.size();

  mtot_local = 0.0;
  vdrift_local[0] = 0.0;
  vdrift_local[1] = 0.0;
  vdrift_local[2] = 0.0;
  
  for(vd = 0; vd < nobj; vd++){
    
    amass = info->integrableObjects[vd]->getMass();
    info->integrableObjects[vd]->getVel( aVel );

    for(j = 0; j < 3; j++) 
      vdrift_local[j] += aVel[j] * amass;
    
    mtot_local += amass;
  }

#ifdef IS_MPI
  MPI_Allreduce(&mtot_local,&mtot,1,MPI_DOUBLE,MPI_SUM, MPI_COMM_WORLD);
  MPI_Allreduce(vdrift_local,vdrift,3,MPI_DOUBLE,MPI_SUM, MPI_COMM_WORLD);
#else
  mtot = mtot_local;
  for(vd = 0; vd < 3; vd++) {
    vdrift[vd] = vdrift_local[vd];
  }
#endif
    
  for (vd = 0; vd < 3; vd++) {
    vdrift[vd] = vdrift[vd] / mtot;
  }
  
}

void Thermo::getCOM(double COM[3]){

  double mtot, mtot_local;
  double aPos[3], amass;
  double COM_local[3];
  int i, j;
  int nobj;

  mtot_local = 0.0;
  COM_local[0] = 0.0;
  COM_local[1] = 0.0;
  COM_local[2] = 0.0;

  nobj = info->integrableObjects.size();
  for(i = 0; i < nobj; i++){
    
    amass = info->integrableObjects[i]->getMass();
    info->integrableObjects[i]->getPos( aPos );

    for(j = 0; j < 3; j++) 
      COM_local[j] += aPos[j] * amass;
    
    mtot_local += amass;
  }

#ifdef IS_MPI
  MPI_Allreduce(&mtot_local,&mtot,1,MPI_DOUBLE,MPI_SUM, MPI_COMM_WORLD);
  MPI_Allreduce(COM_local,COM,3,MPI_DOUBLE,MPI_SUM, MPI_COMM_WORLD);
#else
  mtot = mtot_local;
  for(i = 0; i < 3; i++) {
    COM[i] = COM_local[i];
  }
#endif
    
  for (i = 0; i < 3; i++) {
    COM[i] = COM[i] / mtot;
  }
}

void Thermo::removeCOMdrift() {
  double vdrift[3], aVel[3];
  int vd, j, nobj;

  nobj = info->integrableObjects.size();

  // Get the Center of Mass drift velocity.

  getCOMVel(vdrift);
  
  //  Corrects for the center of mass drift.
  // sums all the momentum and divides by total mass.

  for(vd = 0; vd < nobj; vd++){
    
    info->integrableObjects[vd]->getVel(aVel);
    
    for (j=0; j < 3; j++) 
      aVel[j] -= vdrift[j];
        
    info->integrableObjects[vd]->setVel( aVel );
  }
}
Revision:	1334
Committed:	Fri Jul 16 18:58:03 2004 UTC (20 years ago) by gezelter
File size:	9661 byte(s)
Log Message:	Initial import of OOPSE-1.0 source tree
#	User	Rev	Content
1	gezelter	1334	#include <math.h>
2			#include <iostream>
3			using namespace std;
4
5			#ifdef IS_MPI
6			#include <mpi.h>
7			#endif //is_mpi
8
9			#include "Thermo.hpp"
10			#include "SRI.hpp"
11			#include "Integrator.hpp"
12			#include "simError.h"
13			#include "MatVec3.h"
14
15			#ifdef IS_MPI
16			#define __C
17			#include "mpiSimulation.hpp"
18			#endif // is_mpi
19
20			inline double roundMe( double x ){
21			return ( x >= 0 ) ? floor( x + 0.5 ) : ceil( x - 0.5 );
22			}
23
24			Thermo::Thermo( SimInfo* the_info ) {
25			info = the_info;
26			int baseSeed = the_info->getSeed();
27
28			gaussStream = new gaussianSPRNG( baseSeed );
29			}
30
31			Thermo::~Thermo(){
32			delete gaussStream;
33			}
34
35			double Thermo::getKinetic(){
36
37			const double e_convert = 4.184E-4; // convert kcal/mol -> (amu A^2)/fs^2
38			double kinetic;
39			double amass;
40			double aVel[3], aJ[3], I[3][3];
41			int i, j, k, kl;
42
43			double kinetic_global;
44			vector<StuntDouble *> integrableObjects = info->integrableObjects;
45
46			kinetic = 0.0;
47			kinetic_global = 0.0;
48
49			for (kl=0; kl<integrableObjects.size(); kl++) {
50			integrableObjects[kl]->getVel(aVel);
51			amass = integrableObjects[kl]->getMass();
52
53			for(j=0; j<3; j++)
54			kinetic += amassaVel[j]aVel[j];
55
56			if (integrableObjects[kl]->isDirectional()){
57
58			integrableObjects[kl]->getJ( aJ );
59			integrableObjects[kl]->getI( I );
60
61			if (integrableObjects[kl]->isLinear()) {
62			i = integrableObjects[kl]->linearAxis();
63			j = (i+1)%3;
64			k = (i+2)%3;
65			kinetic += aJ[j]aJ[j]/I[j][j] + aJ[k]aJ[k]/I[k][k];
66			} else {
67			for (j=0; j<3; j++)
68			kinetic += aJ[j]*aJ[j] / I[j][j];
69			}
70			}
71			}
72			#ifdef IS_MPI
73			MPI_Allreduce(&kinetic,&kinetic_global,1,MPI_DOUBLE,
74			MPI_SUM, MPI_COMM_WORLD);
75			kinetic = kinetic_global;
76			#endif //is_mpi
77
78			kinetic = kinetic * 0.5 / e_convert;
79
80			return kinetic;
81			}
82
83			double Thermo::getPotential(){
84
85			double potential_local;
86			double potential;
87			int el, nSRI;
88			Molecule* molecules;
89
90			molecules = info->molecules;
91			nSRI = info->n_SRI;
92
93			potential_local = 0.0;
94			potential = 0.0;
95			potential_local += info->lrPot;
96
97			for( el=0; el<info->n_mol; el++ ){
98			potential_local += molecules[el].getPotential();
99			}
100
101			// Get total potential for entire system from MPI.
102			#ifdef IS_MPI
103			MPI_Allreduce(&potential_local,&potential,1,MPI_DOUBLE,
104			MPI_SUM, MPI_COMM_WORLD);
105			#else
106			potential = potential_local;
107			#endif // is_mpi
108
109			return potential;
110			}
111
112			double Thermo::getTotalE(){
113
114			double total;
115
116			total = this->getKinetic() + this->getPotential();
117			return total;
118			}
119
120			double Thermo::getTemperature(){
121
122			const double kb = 1.9872156E-3; // boltzman's constant in kcal/(mol K)
123			double temperature;
124
125			temperature = ( 2.0 * this->getKinetic() ) / ((double)info->ndf * kb );
126			return temperature;
127			}
128
129			double Thermo::getVolume() {
130
131			return info->boxVol;
132			}
133
134			double Thermo::getPressure() {
135
136			// Relies on the calculation of the full molecular pressure tensor
137
138			const double p_convert = 1.63882576e8;
139			double press[3][3];
140			double pressure;
141
142			this->getPressureTensor(press);
143
144			pressure = p_convert * (press[0][0] + press[1][1] + press[2][2]) / 3.0;
145
146			return pressure;
147			}
148
149			double Thermo::getPressureX() {
150
151			// Relies on the calculation of the full molecular pressure tensor
152
153			const double p_convert = 1.63882576e8;
154			double press[3][3];
155			double pressureX;
156
157			this->getPressureTensor(press);
158
159			pressureX = p_convert * press[0][0];
160
161			return pressureX;
162			}
163
164			double Thermo::getPressureY() {
165
166			// Relies on the calculation of the full molecular pressure tensor
167
168			const double p_convert = 1.63882576e8;
169			double press[3][3];
170			double pressureY;
171
172			this->getPressureTensor(press);
173
174			pressureY = p_convert * press[1][1];
175
176			return pressureY;
177			}
178
179			double Thermo::getPressureZ() {
180
181			// Relies on the calculation of the full molecular pressure tensor
182
183			const double p_convert = 1.63882576e8;
184			double press[3][3];
185			double pressureZ;
186
187			this->getPressureTensor(press);
188
189			pressureZ = p_convert * press[2][2];
190
191			return pressureZ;
192			}
193
194
195			void Thermo::getPressureTensor(double press[3][3]){
196			// returns pressure tensor in units amufs^-2Ang^-1
197			// routine derived via viral theorem description in:
198			// Paci, E. and Marchi, M. J.Phys.Chem. 1996, 100, 4314-4322
199
200			const double e_convert = 4.184e-4;
201
202			double molmass, volume;
203			double vcom[3];
204			double p_local[9], p_global[9];
205			int i, j, k;
206
207			for (i=0; i < 9; i++) {
208			p_local[i] = 0.0;
209			p_global[i] = 0.0;
210			}
211
212			// use velocities of integrableObjects and their masses:
213
214			for (i=0; i < info->integrableObjects.size(); i++) {
215
216			molmass = info->integrableObjects[i]->getMass();
217
218			info->integrableObjects[i]->getVel(vcom);
219
220			p_local[0] += molmass * (vcom[0] * vcom[0]);
221			p_local[1] += molmass * (vcom[0] * vcom[1]);
222			p_local[2] += molmass * (vcom[0] * vcom[2]);
223			p_local[3] += molmass * (vcom[1] * vcom[0]);
224			p_local[4] += molmass * (vcom[1] * vcom[1]);
225			p_local[5] += molmass * (vcom[1] * vcom[2]);
226			p_local[6] += molmass * (vcom[2] * vcom[0]);
227			p_local[7] += molmass * (vcom[2] * vcom[1]);
228			p_local[8] += molmass * (vcom[2] * vcom[2]);
229
230			}
231
232			// Get total for entire system from MPI.
233
234			#ifdef IS_MPI
235			MPI_Allreduce(p_local,p_global,9,MPI_DOUBLE, MPI_SUM, MPI_COMM_WORLD);
236			#else
237			for (i=0; i<9; i++) {
238			p_global[i] = p_local[i];
239			}
240			#endif // is_mpi
241
242			volume = this->getVolume();
243
244
245
246			for(i = 0; i < 3; i++) {
247			for (j = 0; j < 3; j++) {
248			k = 3*i + j;
249			press[i][j] = (p_global[k] + info->tau[k]*e_convert) / volume;
250			}
251			}
252			}
253
254			void Thermo::velocitize() {
255
256			double aVel[3], aJ[3], I[3][3];
257			int i, j, l, m, n, vr, vd; // velocity randomizer loop counters
258			double vdrift[3];
259			double vbar;
260			const double kb = 8.31451e-7; // kb in amu, angstroms, fs, etc.
261			double av2;
262			double kebar;
263			double temperature;
264			int nobj;
265
266			nobj = info->integrableObjects.size();
267
268			temperature = info->target_temp;
269
270			kebar = kb * temperature * (double)info->ndfRaw /
271			( 2.0 * (double)info->ndf );
272
273			for(vr = 0; vr < nobj; vr++){
274
275			// uses equipartition theory to solve for vbar in angstrom/fs
276
277			av2 = 2.0 * kebar / info->integrableObjects[vr]->getMass();
278			vbar = sqrt( av2 );
279
280			// picks random velocities from a gaussian distribution
281			// centered on vbar
282
283			for (j=0; j<3; j++)
284			aVel[j] = vbar * gaussStream->getGaussian();
285
286			info->integrableObjects[vr]->setVel( aVel );
287
288			if(info->integrableObjects[vr]->isDirectional()){
289
290			info->integrableObjects[vr]->getI( I );
291
292			if (info->integrableObjects[vr]->isLinear()) {
293
294			l= info->integrableObjects[vr]->linearAxis();
295			m = (l+1)%3;
296			n = (l+2)%3;
297
298			aJ[l] = 0.0;
299			vbar = sqrt( 2.0 * kebar * I[m][m] );
300			aJ[m] = vbar * gaussStream->getGaussian();
301			vbar = sqrt( 2.0 * kebar * I[n][n] );
302			aJ[n] = vbar * gaussStream->getGaussian();
303
304			} else {
305			for (j = 0 ; j < 3; j++) {
306			vbar = sqrt( 2.0 * kebar * I[j][j] );
307			aJ[j] = vbar * gaussStream->getGaussian();
308			}
309			} // else isLinear
310
311			info->integrableObjects[vr]->setJ( aJ );
312
313			}//isDirectional
314
315			}
316
317			// Get the Center of Mass drift velocity.
318
319			getCOMVel(vdrift);
320
321			// Corrects for the center of mass drift.
322			// sums all the momentum and divides by total mass.
323
324			for(vd = 0; vd < nobj; vd++){
325
326			info->integrableObjects[vd]->getVel(aVel);
327
328			for (j=0; j < 3; j++)
329			aVel[j] -= vdrift[j];
330
331			info->integrableObjects[vd]->setVel( aVel );
332			}
333
334			}
335
336			void Thermo::getCOMVel(double vdrift[3]){
337
338			double mtot, mtot_local;
339			double aVel[3], amass;
340			double vdrift_local[3];
341			int vd, j;
342			int nobj;
343
344			nobj = info->integrableObjects.size();
345
346			mtot_local = 0.0;
347			vdrift_local[0] = 0.0;
348			vdrift_local[1] = 0.0;
349			vdrift_local[2] = 0.0;
350
351			for(vd = 0; vd < nobj; vd++){
352
353			amass = info->integrableObjects[vd]->getMass();
354			info->integrableObjects[vd]->getVel( aVel );
355
356			for(j = 0; j < 3; j++)
357			vdrift_local[j] += aVel[j] * amass;
358
359			mtot_local += amass;
360			}
361
362			#ifdef IS_MPI
363			MPI_Allreduce(&mtot_local,&mtot,1,MPI_DOUBLE,MPI_SUM, MPI_COMM_WORLD);
364			MPI_Allreduce(vdrift_local,vdrift,3,MPI_DOUBLE,MPI_SUM, MPI_COMM_WORLD);
365			#else
366			mtot = mtot_local;
367			for(vd = 0; vd < 3; vd++) {
368			vdrift[vd] = vdrift_local[vd];
369			}
370			#endif
371
372			for (vd = 0; vd < 3; vd++) {
373			vdrift[vd] = vdrift[vd] / mtot;
374			}
375
376			}
377
378			void Thermo::getCOM(double COM[3]){
379
380			double mtot, mtot_local;
381			double aPos[3], amass;
382			double COM_local[3];
383			int i, j;
384			int nobj;
385
386			mtot_local = 0.0;
387			COM_local[0] = 0.0;
388			COM_local[1] = 0.0;
389			COM_local[2] = 0.0;
390
391			nobj = info->integrableObjects.size();
392			for(i = 0; i < nobj; i++){
393
394			amass = info->integrableObjects[i]->getMass();
395			info->integrableObjects[i]->getPos( aPos );
396
397			for(j = 0; j < 3; j++)
398			COM_local[j] += aPos[j] * amass;
399
400			mtot_local += amass;
401			}
402
403			#ifdef IS_MPI
404			MPI_Allreduce(&mtot_local,&mtot,1,MPI_DOUBLE,MPI_SUM, MPI_COMM_WORLD);
405			MPI_Allreduce(COM_local,COM,3,MPI_DOUBLE,MPI_SUM, MPI_COMM_WORLD);
406			#else
407			mtot = mtot_local;
408			for(i = 0; i < 3; i++) {
409			COM[i] = COM_local[i];
410			}
411			#endif
412
413			for (i = 0; i < 3; i++) {
414			COM[i] = COM[i] / mtot;
415			}
416			}
417
418			void Thermo::removeCOMdrift() {
419			double vdrift[3], aVel[3];
420			int vd, j, nobj;
421
422			nobj = info->integrableObjects.size();
423
424			// Get the Center of Mass drift velocity.
425
426			getCOMVel(vdrift);
427
428			// Corrects for the center of mass drift.
429			// sums all the momentum and divides by total mass.
430
431			for(vd = 0; vd < nobj; vd++){
432
433			info->integrableObjects[vd]->getVel(aVel);
434
435			for (j=0; j < 3; j++)
436			aVel[j] -= vdrift[j];
437
438			info->integrableObjects[vd]->setVel( aVel );
439			}
440			}