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ndcg.py
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ndcg.py
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# Copyright The PyTorch Lightning team.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
from typing import Any, Optional
from torch import Tensor, tensor
from torchmetrics.functional.retrieval.ndcg import retrieval_normalized_dcg
from torchmetrics.retrieval.base import RetrievalMetric
class RetrievalNormalizedDCG(RetrievalMetric):
"""Computes `Normalized Discounted Cumulative Gain`_.
Works with binary or positive integer target data. Accepts float predictions from a model output.
As input to ``forward`` and ``update`` the metric accepts the following input:
- ``preds`` (:class:`~torch.Tensor`): A float tensor of shape ``(N, ...)``
- ``target`` (:class:`~torch.Tensor`): A long or bool tensor of shape ``(N, ...)``
- ``indexes`` (:class:`~torch.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:
- ``ndcg`` (:class:`~torch.Tensor`): A single-value tensor with the nDCG of the predictions
``preds`` w.r.t. the labels ``target``
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.
Args:
empty_target_action:
Specify what to do with queries that do not have at least a positive ``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:
Ignore predictions where the target is equal to this number.
k: consider only the top k elements for each query (default: ``None``, which considers them all)
kwargs: Additional keyword arguments, see :ref:`Metric kwargs` for more info.
Raises:
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 ``k`` parameter is not `None` or an integer larger than 0.
Example:
>>> from torchmetrics import RetrievalNormalizedDCG
>>> 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])
>>> ndcg = RetrievalNormalizedDCG()
>>> ndcg(preds, target, indexes=indexes)
tensor(0.8467)
"""
is_differentiable: bool = False
higher_is_better: bool = True
full_state_update: bool = False
def __init__(
self,
empty_target_action: str = "neg",
ignore_index: Optional[int] = None,
k: Optional[int] = None,
**kwargs: Any,
) -> None:
super().__init__(
empty_target_action=empty_target_action,
ignore_index=ignore_index,
**kwargs,
)
if (k is not None) and not (isinstance(k, int) and k > 0):
raise ValueError("`k` has to be a positive integer or None")
self.k = k
self.allow_non_binary_target = True
def _metric(self, preds: Tensor, target: Tensor) -> Tensor:
return retrieval_normalized_dcg(preds, target, k=self.k)