void set_parameter (string_ref name, double value)
{
if (! (value > 0.))
rt_error ("Invalid " + name + " value");
if (name == "temperature")
inv_temperature = 1./value;
else if (name == "inv_temperature")
inv_temperature = value;
else if (name == "cutoff")
cutoff = value;
else if (name == "gauss_epsilon")
gauss_epsilon = value;
else if (name == "gauss_r0")
gauss_r0 = value;
else if (name == "gauss_sigma_sq")
gauss_sigma_sq = value;
else
rt_error ("Invalid parameter: " + name);
if (gauss_r0 < LJ_MINIMUM || cutoff < gauss_r0)
std::cerr << "Code is not correct in this regime" << ABORT;
// precompute some interesting quantities
lj_at_cutoff = evaluate_lj (sq (cutoff));
pref_g = -.5 / gauss_sigma_sq;
g_at_cutoff = evaluate_g (sq (cutoff));
g_at_origin = evaluate_g (sq (0.));
}
double random_attractive_lift_g (double rsq, RandomContext *random)
{
rsq = fmax (rsq, sq (gauss_r0));
// add thermal energy increase on current interaction energy
double e_now = evaluate_g (rsq);
double e_star = random->exponential (inv_temperature);
double e_evt = e_now + e_star;
if (e_evt >= g_at_cutoff)
{
// thermal energy too large, particle escapes to infinity
return ESCAPES_TO_INFINITY ();
}
else
{
// invert the Gauss, picking the solution in attractive region
double r_evt = gauss_r0 + sqrt (log (e_evt / (-gauss_epsilon)) / pref_g);
return sq (r_evt);
}
}
double random_repulsive_lift_g (double rsq, RandomContext *random)
{
rsq = fmin (rsq, sq (gauss_r0));
// add thermal energy increase on current interaction energy
double e_now = evaluate_g (rsq);
double e_star = random->exponential (inv_temperature);
double e_evt = e_now + e_star;
if (e_evt >= g_at_origin)
{
// no event (thermal energy large enough)
return -rsq;
}
else
{
// invert the Gauss, picking the solution in repulsive region
double r_evt = gauss_r0 - sqrt (log (e_evt / (-gauss_epsilon)) / pref_g);
assert (r_evt > 0.);
return sq (r_evt);
}
}
DBL Superellipsoid::evaluate_superellipsoid(const Vector3d& P) const
{
return evaluate_g(evaluate_g(fabs(P[X]), fabs(P[Y]), Power[X]), fabs(P[Z]), Power[Z]) - 1;
}
