def calc_score_diff(score1, score2):
    """
    This function calculates the pairwise score difference for score1 and score2

    @param score1, score2: input scores, dictionary
    @return: score_diff, score difference, a dictionary
    """
    score_diff = {}
    for i in score1.keys():
        score_diff[i] = score1[i] - score2[i]
    return (score_diff)