metrics.py

# -*- encoding: utf-8 -*-


"""
recbole.evaluator.metrics
############################
"""

from logging import getLogger

import numpy as np
from sklearn.metrics import auc as sk_auc
from sklearn.metrics import mean_absolute_error, mean_squared_error


#    TopK Metrics    #


def hit_(pos_index, pos_len):
    r"""Hit_ (also known as hit ratio at :math:`N`) is a way of calculating how many 'hits' you have
    in an n-sized list of ranked items.

    .. _Hit: c

    .. math::
        \mathrm {HR@K} =\frac{Number \space of \space Hits @K}{|GT|}

    :math:`HR` is the number of users with a positive sample in the recommendation list.
    :math:`GT` is the total number of samples in the test set.

    """
    result = np.cumsum(pos_index, axis=1)
    return (result > 0).astype(int)


def mrr_(pos_index, pos_len):
    r"""The MRR_ (also known as mean reciprocal rank) is a statistic measure for evaluating any process
    that produces a list of possible responses to a sample of queries, ordered by probability of correctness.

    .. _MRR: https://en.wikipedia.org/wiki/Mean_reciprocal_rank

    .. math::
        \mathrm {MRR} = \frac{1}{|{U}|} \sum_{i=1}^{|{U}|} \frac{1}{rank_i}

    :math:`U` is the number of users, :math:`rank_i` is the rank of the first item in the recommendation list
    in the test set results for user :math:`i`.

    """
    idxs = pos_index.argmax(axis=1)
    result = np.zeros_like(pos_index, dtype=float)
    for row, idx in enumerate(idxs):
        if pos_index[row, idx] > 0:
            result[row, idx:] = 1 / (idx + 1)
        else:
            result[row, idx:] = 0
    return result


def map_(pos_index, pos_len):
    r"""MAP_ (also known as Mean Average Precision) The MAP is meant to calculate Avg. Precision for the relevant items.

    Note:
        In this case the normalization factor used is :math:`\frac{1}{\min (m,N)}`, which prevents your AP score from
        being unfairly suppressed when your number of recommendations couldn't possibly capture all the correct ones.

    .. _map: http://sdsawtelle.github.io/blog/output/mean-average-precision-MAP-for-recommender-systems.html#MAP-for-Recommender-Algorithms

    .. math::
        \begin{align*}
        \mathrm{AP@N} &= \frac{1}{\mathrm{min}(m,N)}\sum_{k=1}^N P(k) \cdot rel(k) \\
        \mathrm{MAP@N}& = \frac{1}{|U|}\sum_{u=1}^{|U|}(\mathrm{AP@N})_u
        \end{align*}

    """
    pre = precision_(pos_index, pos_len)
    sum_pre = np.cumsum(pre * pos_index.astype(float), axis=1)
    len_rank = np.full_like(pos_len, pos_index.shape[1])
    actual_len = np.where(pos_len > len_rank, len_rank, pos_len)
    result = np.zeros_like(pos_index, dtype=float)
    for row, lens in enumerate(actual_len):
        ranges = np.arange(1, pos_index.shape[1] + 1)
        ranges[lens:] = ranges[lens - 1]
        result[row] = sum_pre[row] / ranges
    return result


def recall_(pos_index, pos_len):
    r"""Recall_ (also known as sensitivity) is the fraction of the total amount of relevant instances
    that were actually retrieved

    .. _recall: https://en.wikipedia.org/wiki/Precision_and_recall#Recall

    .. math::
        \mathrm {Recall@K} = \frac{|Rel_u\cap Rec_u|}{Rel_u}

    :math:`Rel_u` is the set of items relevant to user :math:`U`,
    :math:`Rec_u` is the top K items recommended to users.
    We obtain the result by calculating the average :math:`Recall@K` of each user.

    """
    return np.cumsum(pos_index, axis=1) / pos_len.reshape(-1, 1)


def ndcg_(pos_index, pos_len):
    r"""NDCG_ (also known as normalized discounted cumulative gain) is a measure of ranking quality.
    Through normalizing the score, users and their recommendation list results in the whole test set can be evaluated.

    .. _NDCG: https://en.wikipedia.org/wiki/Discounted_cumulative_gain#Normalized_DCG

    .. math::
        \begin{gather}
            \mathrm {DCG@K}=\sum_{i=1}^{K} \frac{2^{rel_i}-1}{\log_{2}{(i+1)}}\\
            \mathrm {IDCG@K}=\sum_{i=1}^{K}\frac{1}{\log_{2}{(i+1)}}\\
            \mathrm {NDCG_u@K}=\frac{DCG_u@K}{IDCG_u@K}\\
            \mathrm {NDCG@K}=\frac{\sum \nolimits_{u \in U^{te}NDCG_u@K}}{|U^{te}|}
        \end{gather}

    :math:`K` stands for recommending :math:`K` items.
    And the :math:`rel_i` is the relevance of the item in position :math:`i` in the recommendation list.
    :math:`{rel_i}` equals to 1 if the item is ground truth otherwise 0.
    :math:`U^{te}` stands for all users in the test set.

    """
    len_rank = np.full_like(pos_len, pos_index.shape[1])
    idcg_len = np.where(pos_len > len_rank, len_rank, pos_len)

    iranks = np.zeros_like(pos_index, dtype=float)
    iranks[:, :] = np.arange(1, pos_index.shape[1] + 1)
    idcg = np.cumsum(1.0 / np.log2(iranks + 1), axis=1)
    for row, idx in enumerate(idcg_len):
        idcg[row, idx:] = idcg[row, idx - 1]

    ranks = np.zeros_like(pos_index, dtype=float)
    ranks[:, :] = np.arange(1, pos_index.shape[1] + 1)
    dcg = 1.0 / np.log2(ranks + 1)
    dcg = np.cumsum(np.where(pos_index, dcg, 0), axis=1)

    result = dcg / idcg
    return result


def precision_(pos_index, pos_len):
    r"""Precision_ (also called positive predictive value) is the fraction of
    relevant instances among the retrieved instances

    .. _precision: https://en.wikipedia.org/wiki/Precision_and_recall#Precision

    .. math::
        \mathrm {Precision@K} = \frac{|Rel_u \cap Rec_u|}{Rec_u}

    :math:`Rel_u` is the set of items relevant to user :math:`U`,
    :math:`Rec_u` is the top K items recommended to users.
    We obtain the result by calculating the average :math:`Precision@K` of each user.

    """
    return pos_index.cumsum(axis=1) / np.arange(1, pos_index.shape[1] + 1)


def gauc_(user_len_list, pos_len_list, pos_rank_sum):
    r"""GAUC_ (also known as Group Area Under Curve) is used to evaluate the two-class model, referring to
    the area under the ROC curve grouped by user.

    .. _GAUC: https://dl.acm.org/doi/10.1145/3219819.3219823

    Note:
        It calculates the AUC score of each user, and finally obtains GAUC by weighting the user AUC.
        It is also not limited to k. Due to our padding for `scores_tensor` in `RankEvaluator` with
        `-np.inf`, the padding value will influence the ranks of origin items. Therefore, we use
        descending sort here and make an identity transformation  to the formula of `AUC`, which is
        shown in `auc_` function. For readability, we didn't do simplification in the code.

    .. math::
        \mathrm {GAUC} = \frac {{{M} \times {(M+N+1)} - \frac{M \times (M+1)}{2}} -
        \sum\limits_{i=1}^M rank_{i}} {{M} \times {N}}

    :math:`M` is the number of positive samples.
    :math:`N` is the number of negative samples.
    :math:`rank_i` is the descending rank of the ith positive sample.

    """
    neg_len_list = user_len_list - pos_len_list

    # check positive and negative samples
    any_without_pos = np.any(pos_len_list == 0)
    any_without_neg = np.any(neg_len_list == 0)
    non_zero_idx = np.full(len(user_len_list), True, dtype=np.bool)
    if any_without_pos:
        logger = getLogger()
        logger.warning(
            "No positive samples in some users, "
            "true positive value should be meaningless, "
            "these users have been removed from GAUC calculation"
        )
        non_zero_idx *= (pos_len_list != 0)
    if any_without_neg:
        logger = getLogger()
        logger.warning(
            "No negative samples in some users, "
            "false positive value should be meaningless, "
            "these users have been removed from GAUC calculation"
        )
        non_zero_idx *= (neg_len_list != 0)
    if any_without_pos or any_without_neg:
        item_list = user_len_list, neg_len_list, pos_len_list, pos_rank_sum
        user_len_list, neg_len_list, pos_len_list, pos_rank_sum = \
            map(lambda x: x[non_zero_idx], item_list)

    pair_num = (user_len_list + 1) * pos_len_list - pos_len_list * (pos_len_list + 1) / 2 - np.squeeze(pos_rank_sum)
    user_auc = pair_num / (neg_len_list * pos_len_list)
    result = (user_auc * pos_len_list).sum() / pos_len_list.sum()

    return result


#    CTR Metrics    #
def auc_(trues, preds):
    r"""AUC_ (also known as Area Under Curve) is used to evaluate the two-class model, referring to
    the area under the ROC curve

    .. _AUC: https://en.wikipedia.org/wiki/Receiver_operating_characteristic#Area_under_the_curve

    Note:
        This metric does not calculate group-based AUC which considers the AUC scores
        averaged across users. It is also not limited to k. Instead, it calculates the
        scores on the entire prediction results regardless the users.

    .. math::
        \mathrm {AUC} = \frac{\sum\limits_{i=1}^M rank_{i}
        - \frac {{M} \times {(M+1)}}{2}} {{{M} \times {N}}}

    :math:`M` is the number of positive samples.
    :math:`N` is the number of negative samples.
    :math:`rank_i` is the ascending rank of the ith positive sample.

    """
    fps, tps = _binary_clf_curve(trues, preds)

    if len(fps) > 2:
        optimal_idxs = np.where(np.r_[True, np.logical_or(np.diff(fps, 2), np.diff(tps, 2)), True])[0]
        fps = fps[optimal_idxs]
        tps = tps[optimal_idxs]

    tps = np.r_[0, tps]
    fps = np.r_[0, fps]

    if fps[-1] <= 0:
        logger = getLogger()
        logger.warning("No negative samples in y_true, " "false positive value should be meaningless")
        fpr = np.repeat(np.nan, fps.shape)
    else:
        fpr = fps / fps[-1]

    if tps[-1] <= 0:
        logger = getLogger()
        logger.warning("No positive samples in y_true, " "true positive value should be meaningless")
        tpr = np.repeat(np.nan, tps.shape)
    else:
        tpr = tps / tps[-1]

    return sk_auc(fpr, tpr)


# Loss based Metrics #


def mae_(trues, preds):
    r"""`Mean absolute error regression loss`__

    .. __: https://en.wikipedia.org/wiki/Mean_absolute_error

    .. math::
        \mathrm{MAE}=\frac{1}{|{T}|} \sum_{(u, i) \in {T}}\left|\hat{r}_{u i}-r_{u i}\right|

    :math:`T` is the test set, :math:`\hat{r}_{u i}` is the score predicted by the model,
    and :math:`r_{u i}` the actual score of the test set.

    """
    return mean_absolute_error(trues, preds)


def rmse_(trues, preds):
    r"""`Mean std error regression loss`__

    .. __: https://en.wikipedia.org/wiki/Root-mean-square_deviation

    .. math::
        \mathrm{RMSE} = \sqrt{\frac{1}{|{T}|} \sum_{(u, i) \in {T}}(\hat{r}_{u i}-r_{u i})^{2}}

    :math:`T` is the test set, :math:`\hat{r}_{u i}` is the score predicted by the model,
    and :math:`r_{u i}` the actual score of the test set.

    """
    return np.sqrt(mean_squared_error(trues, preds))


def log_loss_(trues, preds):
    r"""`Log loss`__, aka logistic loss or cross-entropy loss

    .. __: http://wiki.fast.ai/index.php/Log_Loss

    .. math::
        -\log {P(y_t|y_p)} = -(({y_t}\ \log{y_p}) + {(1-y_t)}\ \log{(1 - y_p)})

    For a single sample, :math:`y_t` is true label in :math:`\{0,1\}`.
    :math:`y_p` is the estimated probability that :math:`y_t = 1`.

    """
    eps = 1e-15
    preds = float64(preds)
    preds = np.clip(preds, eps, 1 - eps)
    loss = np.sum(-trues * np.log(preds) - (1 - trues) * np.log(1 - preds))

    return loss / len(preds)


def _binary_clf_curve(trues, preds):
    """Calculate true and false positives per binary classification threshold

    Args:
        trues (numpy.ndarray): the true scores' list
        preds (numpy.ndarray): the predict scores' list

    Returns:
        fps (numpy.ndarray): A count of false positives, at index i being the number of negative
        samples assigned a score >= thresholds[i]
        preds (numpy.ndarray): An increasing count of true positives, at index i being the number
        of positive samples assigned a score >= thresholds[i].

    Note:
        To improve efficiency, we referred to the origin code(which is available at sklearn.metrics.roc_curve)
        in SkLearn and made some optimizations.

    """
    trues = (trues == 1)

    desc_idxs = np.argsort(preds)[::-1]
    preds = preds[desc_idxs]
    trues = trues[desc_idxs]

    unique_val_idxs = np.where(np.diff(preds))[0]
    threshold_idxs = np.r_[unique_val_idxs, trues.size - 1]

    tps = np.cumsum(trues)[threshold_idxs]
    fps = 1 + threshold_idxs - tps
    return fps, tps

# Item based Metrics #

# TODO
# def coverage_():
#     raise NotImplementedError

# def gini_index_():
#     raise NotImplementedError

# def shannon_entropy_():
#     raise NotImplementedError

# def diversity_():
#     raise NotImplementedError

"""Function name and function mapper.
Useful when we have to serialize evaluation metric names
and call the functions based on deserialized names
"""
metrics_dict = {
    'ndcg': ndcg_,
    'hit': hit_,
    'precision': precision_,
    'map': map_,
    'recall': recall_,
    'mrr': mrr_,
    'rmse': rmse_,
    'mae': mae_,
    'logloss': log_loss_,
    'auc': auc_,
    'gauc': gauc_
}