Port correct calculation of phi and alpha to mad macro

[giadarol]

Already implemented and tested in python

def find_alpha_and_phi(dpx, dpy):

    absphi = np.sqrt(dpx ** 2 + dpy ** 2) / 2.0

    if absphi < 1e-20:
        phi = absphi
        alpha = 0.0
    else:
        if dpy>=0.:
            if dpx>=0:
                # First quadrant
                if np.abs(dpx) >= np.abs(dpy):
                    # First octant
                    phi = absphi
                    alpha = np.arctan(dpy/dpx)
                else:
                    # Second octant
                    phi = absphi
                    alpha = 0.5*np.pi - np.arctan(dpx/dpy)
            else: #dpx<0
                # Second quadrant
                if np.abs(dpx) <  np.abs(dpy):
                    # Third octant
                    phi = absphi
                    alpha = 0.5*np.pi - np.arctan(dpx/dpy)
                else:
                    # Forth  octant
                    phi = -absphi
                    alpha = np.arctan(dpy/dpx)
        else: #dpy<0
            if dpx<=0:
                # Third quadrant
                if np.abs(dpx) >= np.abs(dpy):
                    # Fifth octant
                    phi = -absphi
                    alpha = np.arctan(dpy/dpx)
                else:
                    # Sixth octant
                    phi = -absphi
                    alpha = 0.5*np.pi - np.arctan(dpx/dpy)
            else: #dpx>0
                # Forth quadrant
                if np.abs(dpx) <= np.abs(dpy):
                    # Seventh octant
                    phi = -absphi
                    alpha = 0.5*np.pi - np.arctan(dpx/dpy)
                else:
                    # Eighth octant
                    phi = absphi
                    alpha = np.arctan(dpy/dpx)

    return alpha, phi

[giadarol]

@giadarol Remember to copy pysixtrack!!!!

[giadarol]

Done, see:
dc0b809

Still to be tested within mask