/* Get the center from local positions that already have the correct
* PBC representation */
extern void get_center_comm(
const t_commrec *cr,
rvec x_loc[], /* Local positions */
real weight_loc[], /* Local masses or other weights */
int nr_loc, /* Local number of atoms */
int nr_group, /* Total number of atoms of the group */
rvec center) /* Weighted center */
{
double weight_sum, denom;
dvec dsumvec;
double buf[4];
weight_sum = get_sum_of_positions(x_loc, weight_loc, nr_loc, dsumvec);
/* Add the local contributions from all nodes. Put the sum vector and the
* weight in a buffer array so that we get along with a single communication
* call. */
if (PAR(cr))
{
buf[0] = dsumvec[XX];
buf[1] = dsumvec[YY];
buf[2] = dsumvec[ZZ];
buf[3] = weight_sum;
/* Communicate buffer */
gmx_sumd(4, buf, cr);
dsumvec[XX] = buf[0];
dsumvec[YY] = buf[1];
dsumvec[ZZ] = buf[2];
weight_sum = buf[3];
}
if (weight_loc != nullptr)
{
denom = 1.0/weight_sum; /* Divide by the sum of weight to get center of mass e.g. */
}
else
{
denom = 1.0/nr_group; /* Divide by the number of atoms to get the geometrical center */
}
center[XX] = dsumvec[XX]*denom;
center[YY] = dsumvec[YY]*denom;
center[ZZ] = dsumvec[ZZ]*denom;
}
/* Determine center of structure from collective positions x */
extern void get_center(rvec x[], real weight[], const int nr, rvec rcenter)
{
dvec dcenter;
double weight_sum, denom;
weight_sum = get_sum_of_positions(x, weight, nr, dcenter);
if (weight != NULL)
denom = weight_sum; /* Divide by the sum of weight */
else
denom = nr; /* Divide by the number of atoms */
dsvmul(1.0/denom, dcenter, dcenter);
rcenter[XX] = dcenter[XX];
rcenter[YY] = dcenter[YY];
rcenter[ZZ] = dcenter[ZZ];
}