Serial md code

#ifndef FORCESH
#define FORCESH

#include <stdbool.h>
#include "global.h"
#include "atom.h"

static const double rc  = 3.0;   /* outer cutoff radius */
static const double rcp = 2.5;   /* inner cutoff, or start of smoothing */

typedef signed char packed_int;
#define plusx 0x01
#define minux 0x02
#define plusy 0x04
#define minuy 0x08
#define plusz 0x10
#define minuz 0x20
#define pack2x(pack)  (((pack)&minux)?-1:(((pack)&plusx)?1:0))
#define pack2y(pack)  (((pack)&minuy)?-1:(((pack)&plusy)?1:0))
#define pack2z(pack)  (((pack)&minuz)?-1:(((pack)&plusz)?1:0))

typedef struct interaction_pairs_t {
    long long   npairs; /* number of currently stored interaction pairs */
    int*        pairi;  /* current index in atoms of the first atom of each pair */
    int*        pairj;  /* current index in atoms of the second atom of each pair */
    packed_int* dj;     /* shifts in x,y, and z to apply to second
                           atom (either -1, 0, or 1); these shifts
                           accounts for periodic boundary conditions */
} interaction_pairs_t;

void interaction_pairs_alloc(interaction_pairs_t* p, long long Npairsmax);
void interaction_pairs_free(interaction_pairs_t* p);
double computeForces(int N, atom_t atoms[], interaction_pairs_t* p, double L, bool accum);

#endif