def _deriv_logaddexp2(x1, x2):
    """The derivative of f(x, y) = log2(2^x + 2^y)"""
    y1 = np.exp2(x1)
    y2 = np.exp2(x2)
    df_dx1 = y1 / (y1 + y2)
    df_dx2 = y2 / (y1 + y2)
    return np.vstack([df_dx1, df_dx2]).T
def _deriv_logaddexp2 ( x1 , x2 ) : y1 = np . exp2 ( x1 ) y2 = np . exp2 ( x2 ) df_dx1 = y1 / ( y1 + y2 ) df_dx2 = y2 / ( y1 + y2 ) return np . vstack ( [ df_dx1 , df_dx2 ] ) . T
The derivative of f(x, y) = log2(2^x + 2^y)