peano.h

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#ifndef PEANO_H
#define PEANO_H
 
#include <stddef.h>
#include <stdint.h>
 
typedef uint64_t peano_t;
 
#define  BITS_PER_DIMENSION 21  /* for Peano-Hilbert order. Note: Maximum is 10 to fit in 32-bit integer ! */
#define  PEANOCELLS (((peano_t)1)<<(3*BITS_PER_DIMENSION))
 
peano_t peano_hilbert_key(int x, int y, int z, int bits);
 
static inline peano_t PEANO(double *Pos, double BoxSize)
{
    /*No reason known for the Box/2000 and 1.001 factors*/
    const double DomainFac = 1.0 / (BoxSize*1.001) * (((peano_t) 1) << (BITS_PER_DIMENSION));
    const double spos[3] = {Pos[0] + BoxSize/2000, Pos[1] + BoxSize/2000, Pos[2] + BoxSize/2000};
    return peano_hilbert_key(spos[0]*DomainFac, spos[1]*DomainFac, spos[2]*DomainFac, BITS_PER_DIMENSION);
}
 
#define DomainFac(len) ( 1.0 / (len) * (((peano_t) 1) << (BITS_PER_DIMENSION)))
 
void mysort_peano(void *b, size_t n, size_t s, int (*cmp) (const void *, const void *));
 
void init_peano_map(void);
 
#endif