nbody_internal.h

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#ifndef NBODY_INTERNAL_H
#define NBODY_INTERNAL_H
 
#include "nbody_types.h"
 
static const double HALF = 0.5;
 
/* Per-pair Plummer softening: ε² = max(NBODY_SOFTENING_SQ, (F·(r_i+r_j))²). */
static inline double pair_softening_sq(double radius_i, double radius_j)
{
    double sum_r = radius_i + radius_j;
    double eps = (double)NBODY_SOFTENING_FACTOR * sum_r;
    double eps_sq = eps * eps;
    return eps_sq > (double)NBODY_SOFTENING_SQ ? eps_sq
                                               : (double)NBODY_SOFTENING_SQ;
}
 
#endif /* NBODY_INTERNAL_H */