a = spl0; spl0 = spl2; spl2 = a; a = spl1; spl1 = spl3; spl3 = a;
atomic_exch(spl0,spl2); atomic_exch(spl1,spl3);
@sample a = spl0; b = spl1; c = spl2; d = spl3; spl0 = c; spl1 = d; spl2 = a; spl3 = b;