gistfile1.py

def compute_grad_metric(w, x1, x2, label1, label2):
    
    y = label1 == label2
    dx = (x1 - x2).reshape(64, 1)
    mod_x = w.dot(dx)
    if y:
        return 2 * np.dot(w, np.dot(dx, dx.T))
    elif (1 - np.dot(mod_x.T, mod_x) > 0):
        return -2 * np.dot(w, np.dot(dx, dx.T))
    else:
        return np.zeros(w.shape)