Retrieval Fall-Out

Module Interface

class torchmetrics.retrieval.RetrievalFallOut(empty_target_action='pos', ignore_index=None, top_k=None, **kwargs)[source]

Compute Fall-out.

Works with binary target data. Accepts float predictions from a model output.

As input to forward and update the metric accepts the following input:

  • preds (Tensor): A float tensor of shape (N, ...)

  • target (Tensor): A long or bool tensor of shape (N, ...)

  • indexes (Tensor): A long tensor of shape (N, ...) which indicate to which query a prediction belongs

As output to forward and compute the metric returns the following output:

  • fo@k (Tensor): A tensor with the computed metric

All indexes, preds and target must have the same dimension and will be flatten at the beginning, so that for example, a tensor of shape (N, M) is treated as (N * M, ). Predictions will be first grouped by indexes and then will be computed as the mean of the metric over each query.

  • empty_target_action (str) –

    Specify what to do with queries that do not have at least a negative target. Choose from:

    • 'neg': those queries count as 0.0 (default)

    • 'pos': those queries count as 1.0

    • 'skip': skip those queries; if all queries are skipped, 0.0 is returned

    • 'error': raise a ValueError

  • ignore_index (Optional[int]) – Ignore predictions where the target is equal to this number.

  • top_k (Optional[int]) – Consider only the top k elements for each query (default: None, which considers them all)

  • kwargs (Any) – Additional keyword arguments, see Advanced metric settings for more info.

  • ValueError – If empty_target_action is not one of error, skip, neg or pos.

  • ValueError – If ignore_index is not None or an integer.

  • ValueError – If top_k is not None or not an integer greater than 0.


>>> from torchmetrics.retrieval import RetrievalFallOut
>>> indexes = tensor([0, 0, 0, 1, 1, 1, 1])
>>> preds = tensor([0.2, 0.3, 0.5, 0.1, 0.3, 0.5, 0.2])
>>> target = tensor([False, False, True, False, True, False, True])
>>> fo = RetrievalFallOut(top_k=2)
>>> fo(preds, target, indexes=indexes)
plot(val=None, ax=None)[source]

Plot a single or multiple values from the metric.

  • val (Union[Tensor, Sequence[Tensor], None]) – Either a single result from calling metric.forward or metric.compute or a list of these results. If no value is provided, will automatically call metric.compute and plot that result.

  • ax (Optional[Axes]) – An matplotlib axis object. If provided will add plot to that axis

Return type:

Tuple[Figure, Union[Axes, ndarray]]


Figure and Axes object


ModuleNotFoundError – If matplotlib is not installed

>>> import torch
>>> from torchmetrics.retrieval import RetrievalFallOut
>>> # Example plotting a single value
>>> metric = RetrievalFallOut()
>>> metric.update(torch.rand(10,), torch.randint(2, (10,)), indexes=torch.randint(2,(10,)))
>>> fig_, ax_ = metric.plot()
>>> import torch
>>> from torchmetrics.retrieval import RetrievalFallOut
>>> # Example plotting multiple values
>>> metric = RetrievalFallOut()
>>> values = []
>>> for _ in range(10):
...     values.append(metric(torch.rand(10,), torch.randint(2, (10,)), indexes=torch.randint(2,(10,))))
>>> fig, ax = metric.plot(values)

Functional Interface

torchmetrics.functional.retrieval.retrieval_fall_out(preds, target, top_k=None)[source]

Compute the Fall-out for information retrieval, as explained in IR Fall-out.

Fall-out is the fraction of non-relevant documents retrieved among all the non-relevant documents.

preds and target should be of the same shape and live on the same device. If no target is True, 0 is returned. target must be either bool or integers and preds must be float, otherwise an error is raised. If you want to measure Fall-out@K, top_k must be a positive integer.

  • preds (Tensor) – estimated probabilities of each document to be relevant.

  • target (Tensor) – ground truth about each document being relevant or not.

  • top_k (Optional[int]) – consider only the top k elements (default: None, which considers them all)

Return type:



A single-value tensor with the fall-out (at top_k) of the predictions preds w.r.t. the labels target


ValueError – If top_k parameter is not None or an integer larger than 0


>>> from  torchmetrics.functional import retrieval_fall_out
>>> preds = tensor([0.2, 0.3, 0.5])
>>> target = tensor([True, False, True])
>>> retrieval_fall_out(preds, target, top_k=2)