static double v_ewald_lr(double beta,double r)
{
if (r == 0)
{
return beta*2/sqrt(M_PI);
}
else
{
return gmx_erfd(beta*r)/r;
}
}
/*! \brief Compute y=(a0+a1)/2-(a0-a1)/2*erf((x-a2)/a3^2) */
static double lmc_erffit (double x, const double *a)
{
double erfarg;
double myerf;
if (a[3] != 0)
{
erfarg = (x-a[2])/(a[3]*a[3]);
myerf = gmx_erfd(erfarg);
}
else
{
/* If a[3] == 0, a[3]^2 = 0 and the erfarg becomes +/- infinity */
if (x < a[2])
{
myerf = -1;
}
else
{
myerf = 1;
}
}
return 0.5*((a[0]+a[1]) - (a[0]-a[1])*myerf);
}