def minimize_score_over_partitions(partitions):
    """
    :param partitions: list of dicts containing 'score'
    :return: index of partition that minimizes the score
    """
    assert isinstance(partitions, list)
    min_score = float('inf')
    min_idx = -1
    for i, p in enumerate(partitions):
        if p['score'] < min_score:
            min_score = p['score']
            min_idx = i
    return min_idx