def LB_commutation_grad(C, ev_sqdiff):
    """
    Compute the gradient of the LB commutativity constraint

    Parameters
    ---------------------
    C         : (K2,K1) Functional map
    ev_sqdiff : (K2,K1) [normalized] matrix of squared eigenvalue differences

    Output
    ---------------------
    gradient : (K2,K1) gradient of the LB commutativity squared norm
    """
    return C * ev_sqdiff