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Computes precision@k of the predictions with respect to sparse labels.

If class_id is specified, we calculate precision by considering only the entries in the batch for which class_id is in the top-k highest predictions, and computing the fraction of them for which class_id is indeed a correct label. If class_id is not specified, we'll calculate precision as how often on average a class among the top-k classes with the highest predicted values of a batch entry is correct and can be found in the label for that entry.

precision_at_k creates two local variables, true_positive_at_<k> and false_positive_at_<k>, that are used to compute the precision@k frequency. This frequency is ultimately returned as precision_at_<k>: an idempotent operation that simply divides true_positive_at_<k> by total (true_positive_at_<k> + false_positive_at_<k>).

For estimation of the metric over a stream of data, the function creates an update_op operation that updates these variables and returns the precision_at_<k>. Internally, a top_k operation computes a Tensor indicating the top k predictions. Set operations applied to top_k and labels calculate the true positives and false positives weighted by weights. Then update_op increments true_positive_at_<k> and false_positive_at_<k> using these values.

If weights is None, weights default to 1. Use weights of 0 to mask values.

labels int64 Tensor or SparseTensor with shape [D1, ... DN, num_labels] or [D1, ... DN], where the latter implies num_labels=1. N >= 1 and num_labels is the number of target classes for the associated prediction. Commonly, N=1 and labels has shape [batch_size, num_labels]. [D1, ... DN] must match predictions. Values should be in range [0, num_classes), where num_classes is the last dimension of predictions. Values outside this range are ignored.
predictions Float Tensor with shape [D1, ... DN, num_classes] where N >= 1. Commonly, N=1 and predictions has shape [batch size, num_classes]. The final dimension contains the logit values for each class. [D1, ... DN] must match labels.
k Integer, k for @k metric.
class_id Integer class ID for which we want binary metrics. This should be in range [0, num_classes], where num_classes is the last dimension of predictions. If class_id is outside this range, the method returns NAN.
weights Tensor whose rank is either 0, or n-1, where n is the rank of labels. If the latter, it must be broadcastable to labels (i.e., all dimensions must be either 1, or the same as the corresponding labels dimension).
metrics_collections An optional list of collections that values should be added to.
updates_collections An optional list of collections that updates should be added to.
name Name of new update operation, and namespace for other dependent ops.

precision Scalar float64 Tensor with the value of true_positives divided by the sum of true_positives and false_positives.
update_op Operation that increments true_positives and false_positives variables appropriately, and whose value matches precision.

ValueError If weights is not None and its shape doesn't match predictions, or if either metrics_collections or updates_collections are not a list or tuple.
RuntimeError If eager execution is enabled.