def calculate_precision_at_equal_recall_rate(predictions, actuals):
"""Performs a local (numpy) calculation of the PERR.
Args:
predictions: Matrix containing the outputs of the model.
Dimensions are 'batch' x 'num_classes'.
actuals: Matrix containing the ground truth labels.
Dimensions are 'batch' x 'num_classes'.
Returns:
float: The average precision at equal recall rate across the entire batch.
"""
aggregated_precision = 0.0
num_videos = actuals.shape[0]
for row in numpy.arange(num_videos):
num_labels = int(numpy.sum(actuals[row]))
top_indices = numpy.argpartition(predictions[row],
-num_labels)[-num_labels:]
item_precision = 0.0
for label_index in top_indices:
if predictions[row][label_index] > 0:
item_precision += actuals[row][label_index]
item_precision /= top_indices.size
aggregated_precision += item_precision
aggregated_precision /= num_videos
return aggregated_precision
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