uint32_hilbert()

static uint64_t uint32_hilbert ( uint32_t  px, uint32_t  py  )

inlinestatic

Definition at line 815 of file gbox.c.

{
        uint64_t x = px;
        uint64_t y = py;
 
        uint64_t A, B, C, D;
 
        // Initial prefix scan round, prime with x and y
        {
                uint64_t a = x ^ y;
                uint64_t b = 0xFFFFFFFFULL ^ a;
                uint64_t c = 0xFFFFFFFFULL ^ (x | y);
                uint64_t d = x & (y ^ 0xFFFFFFFFULL);
 
                A = a | (b >> 1);
                B = (a >> 1) ^ a;
                C = ((c >> 1) ^ (b & (d >> 1))) ^ c;
                D = ((a & (c >> 1)) ^ (d >> 1)) ^ d;
        }
 
        {
                uint64_t a = A;
                uint64_t b = B;
                uint64_t c = C;
                uint64_t d = D;
 
                A = ((a & (a >> 2)) ^ (b & (b >> 2)));
                B = ((a & (b >> 2)) ^ (b & ((a ^ b) >> 2)));
                C ^= ((a & (c >> 2)) ^ (b & (d >> 2)));
                D ^= ((b & (c >> 2)) ^ ((a ^ b) & (d >> 2)));
        }
 
        {
                uint64_t a = A;
                uint64_t b = B;
                uint64_t c = C;
                uint64_t d = D;
 
                A = ((a & (a >> 4)) ^ (b & (b >> 4)));
                B = ((a & (b >> 4)) ^ (b & ((a ^ b) >> 4)));
                C ^= ((a & (c >> 4)) ^ (b & (d >> 4)));
                D ^= ((b & (c >> 4)) ^ ((a ^ b) & (d >> 4)));
        }
 
        {
                uint64_t a = A;
                uint64_t b = B;
                uint64_t c = C;
                uint64_t d = D;
 
                A = ((a & (a >> 8)) ^ (b & (b >> 8)));
                B = ((a & (b >> 8)) ^ (b & ((a ^ b) >> 8)));
                C ^= ((a & (c >> 8)) ^ (b & (d >> 8)));
                D ^= ((b & (c >> 8)) ^ ((a ^ b) & (d >> 8)));
        }
 
        {
                uint64_t a = A;
                uint64_t b = B;
                uint64_t c = C;
                uint64_t d = D;
 
                C ^= ((a & (c >> 16)) ^ (b & (d >> 16)));
                D ^= ((b & (c >> 16)) ^ ((a ^ b) & (d >> 16)));
        }
 
        // Undo transformation prefix scan
        uint64_t a = C ^ (C >> 1);
        uint64_t b = D ^ (D >> 1);
 
        // Recover index bits
        uint64_t i0 = x ^ y;
        uint64_t i1 = b | (0xFFFFFFFFULL ^ (i0 | a));
 
        return uint64_interleave_2(i0, i1);
}

References uint64_interleave_2(), pixval::x, and pixval::y.

Referenced by gbox_get_sortable_hash().

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