50 const int idx2 = idx -1;
51 index[3] = idx2/(lx * lx * lx) ;
52 index[2] = (idx2 - (lx*lx*lx)*index[3])/(lx * lx);
53 index[1] = (idx2 - (lx*lx*lx)*index[3] - (lx*lx) * index[2]) / lx;
54 index[0] = (idx2 - (lx*lx*lx)*index[3] - (lx*lx) * index[2]) - lx*index[1];