static void computeAmoebaStretchBendForces( Context& context, AmoebaStretchBendForce& amoebaStretchBendForce,
std::vector<Vec3>& expectedForces, double* expectedEnergy, FILE* log ) {
// get positions and zero forces
State state = context.getState(State::Positions);
std::vector<Vec3> positions = state.getPositions();
expectedForces.resize( positions.size() );
for( unsigned int ii = 0; ii < expectedForces.size(); ii++ ){
expectedForces[ii][0] = expectedForces[ii][1] = expectedForces[ii][2] = 0.0;
}
// calculates forces/energy
*expectedEnergy = 0.0;
for( int ii = 0; ii < amoebaStretchBendForce.getNumStretchBends(); ii++ ){
computeAmoebaStretchBendForce(ii, positions, amoebaStretchBendForce, expectedForces, expectedEnergy, log );
}
#ifdef AMOEBA_DEBUG
if( log ){
(void) fprintf( log, "computeAmoebaStretchBendForces: expected energy=%14.7e\n", *expectedEnergy );
for( unsigned int ii = 0; ii < positions.size(); ii++ ){
(void) fprintf( log, "%6u [%14.7e %14.7e %14.7e]\n", ii, expectedForces[ii][0], expectedForces[ii][1], expectedForces[ii][2] );
}
(void) fflush( log );
}
#endif
return;
}
void testOneStretchBend( FILE* log ) {
System system;
int numberOfParticles = 3;
for( int ii = 0; ii < numberOfParticles; ii++ ){
system.addParticle(1.0);
}
LangevinIntegrator integrator(0.0, 0.1, 0.01);
AmoebaStretchBendForce* amoebaStretchBendForce = new AmoebaStretchBendForce();
double abLength = 0.144800000E+01;
double cbLength = 0.101500000E+01;
double angleStretchBend = 0.108500000E+03*DegreesToRadians;
//double kStretchBend = 0.750491578E-01;
double kStretchBend = 1.0;
amoebaStretchBendForce->addStretchBend(0, 1, 2, abLength, cbLength, angleStretchBend, kStretchBend );
system.addForce(amoebaStretchBendForce);
Context context(system, integrator, Platform::getPlatformByName( "CUDA"));
std::vector<Vec3> positions(numberOfParticles);
positions[0] = Vec3( 0.262660000E+02, 0.254130000E+02, 0.284200000E+01 );
positions[1] = Vec3( 0.273400000E+02, 0.244300000E+02, 0.261400000E+01 );
positions[2] = Vec3( 0.269573220E+02, 0.236108860E+02, 0.216376800E+01 );
context.setPositions(positions);
compareWithExpectedForceAndEnergy( context, *amoebaStretchBendForce, TOL, "testOneStretchBend", log );
// Try changing the stretch-bend parameters and make sure it's still correct.
amoebaStretchBendForce->setStretchBendParameters(0, 0, 1, 2, 1.1*abLength, 1.2*cbLength, 1.3*angleStretchBend, 1.4*kStretchBend);
bool exceptionThrown = false;
try {
// This should throw an exception.
compareWithExpectedForceAndEnergy( context, *amoebaStretchBendForce, TOL, "testOneStretchBend", log );
}
catch (std::exception ex) {
exceptionThrown = true;
}
ASSERT(exceptionThrown);
amoebaStretchBendForce->updateParametersInContext(context);
compareWithExpectedForceAndEnergy( context, *amoebaStretchBendForce, TOL, "testOneStretchBend", log );
}
static void computeAmoebaStretchBendForces(Context& context, AmoebaStretchBendForce& amoebaStretchBendForce,
std::vector<Vec3>& expectedForces, double* expectedEnergy) {
// get positions and zero forces
State state = context.getState(State::Positions);
std::vector<Vec3> positions = state.getPositions();
expectedForces.resize(positions.size());
for (unsigned int ii = 0; ii < expectedForces.size(); ii++) {
expectedForces[ii][0] = expectedForces[ii][1] = expectedForces[ii][2] = 0.0;
}
// calculates forces/energy
*expectedEnergy = 0.0;
for (int ii = 0; ii < amoebaStretchBendForce.getNumStretchBends(); ii++) {
computeAmoebaStretchBendForce(ii, positions, amoebaStretchBendForce, expectedForces, expectedEnergy);
}
}
static void computeAmoebaStretchBendForce(int bondIndex, std::vector<Vec3>& positions, AmoebaStretchBendForce& amoebaStretchBendForce,
std::vector<Vec3>& forces, double* energy, FILE* log ) {
int particle1, particle2, particle3;
double abBondLength, cbBondLength, angleStretchBend, kStretchBend;
amoebaStretchBendForce.getStretchBendParameters(bondIndex, particle1, particle2, particle3, abBondLength, cbBondLength, angleStretchBend, kStretchBend);
angleStretchBend *= RADIAN;
#ifdef AMOEBA_DEBUG
if( log ){
(void) fprintf( log, "computeAmoebaStretchBendForce: bond %d [%d %d %d] ab=%10.3e cb=%10.3e angle=%10.3e k=%10.3e\n",
bondIndex, particle1, particle2, particle3, abBondLength, cbBondLength, angleStretchBend, kStretchBend );
(void) fflush( log );
}
#endif
enum { A, B, C, LastAtomIndex };
enum { AB, CB, CBxAB, ABxP, CBxP, LastDeltaIndex };
// ---------------------------------------------------------------------------------------
// get deltaR between various combinations of the 3 atoms
// and various intermediate terms
double deltaR[LastDeltaIndex][3];
double rAB2 = 0.0;
double rCB2 = 0.0;
for( int ii = 0; ii < 3; ii++ ){
deltaR[AB][ii] = positions[particle1][ii] - positions[particle2][ii];
rAB2 += deltaR[AB][ii]*deltaR[AB][ii];
deltaR[CB][ii] = positions[particle3][ii] - positions[particle2][ii];
rCB2 += deltaR[CB][ii]*deltaR[CB][ii];
}
double rAB = sqrt( rAB2 );
double rCB = sqrt( rCB2 );
crossProductVector3( deltaR[CB], deltaR[AB], deltaR[CBxAB] );
double rP = dotVector3( deltaR[CBxAB], deltaR[CBxAB] );
rP = sqrt( rP );
if( rP <= 0.0 ){
return;
}
double dot = dotVector3( deltaR[CB], deltaR[AB] );
double cosine = dot/(rAB*rCB);
double angle;
if( cosine >= 1.0 ){
angle = 0.0;
} else if( cosine <= -1.0 ){
angle = PI_M;
} else {
angle = RADIAN*acos(cosine);
}
double termA = -RADIAN/(rAB2*rP);
double termC = RADIAN/(rCB2*rP);
// P = CBxAB
crossProductVector3( deltaR[AB], deltaR[CBxAB], deltaR[ABxP] );
crossProductVector3( deltaR[CB], deltaR[CBxAB], deltaR[CBxP] );
for( int ii = 0; ii < 3; ii++ ){
deltaR[ABxP][ii] *= termA;
deltaR[CBxP][ii] *= termC;
}
double dr = rAB - abBondLength + rCB - cbBondLength;
termA = 1.0/rAB;
termC = 1.0/rCB;
double term = kStretchBend;
// ---------------------------------------------------------------------------------------
// forces
// calculate forces for atoms a, b, c
// the force for b is then -( a + c)
double subForce[LastAtomIndex][3];
double dt = angle - angleStretchBend;
for( int jj = 0; jj < 3; jj++ ){
subForce[A][jj] = term*(dt*termA*deltaR[AB][jj] + dr*deltaR[ABxP][jj] );
subForce[C][jj] = term*(dt*termC*deltaR[CB][jj] + dr*deltaR[CBxP][jj] );
subForce[B][jj] = -( subForce[A][jj] + subForce[C][jj] );
}
// ---------------------------------------------------------------------------------------
// accumulate forces and energy
forces[particle1][0] -= subForce[0][0];
forces[particle1][1] -= subForce[0][1];
forces[particle1][2] -= subForce[0][2];
forces[particle2][0] -= subForce[1][0];
forces[particle2][1] -= subForce[1][1];
forces[particle2][2] -= subForce[1][2];
forces[particle3][0] -= subForce[2][0];
forces[particle3][1] -= subForce[2][1];
forces[particle3][2] -= subForce[2][2];
*energy += term*dt*dr;
#ifdef AMOEBA_DEBUG
if( log ){
(void) fprintf( log, "computeAmoebaStretchBendForce: angle=%10.3e dt=%10.3e dr=%10.3e\n", angle, dt, dr );
(void) fflush( log );
}
#endif
return;
}