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Source code for torch_uncertainty.metrics.classification.brier_score

from typing import Literal

import torch
import torch.nn.functional as F
from torch import Tensor
from torchmetrics import Metric
from torchmetrics.utilities.data import dim_zero_cat


[docs]class BrierScore(Metric): is_differentiable: bool = True higher_is_better: bool | None = False full_state_update: bool = False def __init__( self, num_classes: int, top_class: bool = False, reduction: Literal["mean", "sum", "none", None] = "mean", **kwargs, ) -> None: r"""The Brier Score Metric. Args: num_classes (int): Number of classes top_class (bool, optional): If true, compute the Brier score for the top class only. Defaults to False. reduction (str, optional): Determines how to reduce over the :math:`B`/batch dimension: - ``'mean'`` [default]: Averages score across samples - ``'sum'``: Sum score across samples - ``'none'`` or ``None``: Returns score per sample kwargs: Additional keyword arguments, see `Advanced metric settings <https://torchmetrics.readthedocs.io/en/stable/pages/overview.html#metric-kwargs>`_. Inputs: - :attr:`probs`: :math:`(B, C)` or :math:`(B, N, C)` - :attr:`target`: :math:`(B)` or :math:`(B, C)` where :math:`B` is the batch size, :math:`C` is the number of classes and :math:`N` is the number of estimators. Note: If :attr:`probs` is a 3d tensor, then the metric computes the mean of the Brier score over the estimators ie. :math:`t = \frac{1}{N} \sum_{i=0}^{N-1} BrierScore(probs[:,i,:], target)`. Warning: Make sure that the probabilities in :attr:`probs` are normalized to sum to one. Raises: ValueError: If :attr:`reduction` is not one of ``'mean'``, ``'sum'``, ``'none'`` or ``None``. """ super().__init__(**kwargs) allowed_reduction = ("sum", "mean", "none", None) if reduction not in allowed_reduction: raise ValueError( "Expected argument `reduction` to be one of ", f"{allowed_reduction} but got {reduction}", ) self.num_classes = num_classes self.top_class = top_class self.reduction = reduction self.num_estimators = 1 if self.reduction in ["mean", "sum"]: self.add_state("values", default=torch.tensor(0.0), dist_reduce_fx="sum") else: self.add_state("values", default=[], dist_reduce_fx="cat") self.add_state("total", default=torch.tensor(0), dist_reduce_fx="sum")
[docs] def update(self, probs: Tensor, target: Tensor) -> None: """Update the current Brier score with a new tensor of probabilities. Args: probs (Tensor): A probability tensor of shape (batch, num_estimators, num_classes) or (batch, num_classes) target (Tensor): A tensor of ground truth labels of shape (batch, num_classes) or (batch) """ if target.ndim == 1 and self.num_classes > 1: target = F.one_hot(target, self.num_classes) if probs.ndim <= 2: batch_size = probs.size(0) elif probs.ndim == 3: batch_size = probs.size(0) self.num_estimators = probs.size(1) target = target.unsqueeze(1).repeat(1, self.num_estimators, 1) else: raise ValueError( f"Expected `probs` to be of shape (batch, num_classes) or " f"(batch, num_estimators, num_classes) but got {probs.shape}" ) if self.top_class: probs, indices = probs.max(dim=-1) target = target.gather(-1, indices.unsqueeze(-1)).squeeze(-1) brier_score = F.mse_loss(probs, target, reduction="none") else: brier_score = F.mse_loss(probs, target, reduction="none").sum(dim=-1) if self.reduction is None or self.reduction == "none": self.values.append(brier_score) else: self.values += brier_score.sum() self.total += batch_size
[docs] def compute(self) -> Tensor: """Compute the final Brier score based on inputs passed to ``update``. Returns: Tensor: The final value(s) for the Brier score """ values = dim_zero_cat(self.values) if self.reduction == "sum": return values.sum(dim=-1) / self.num_estimators if self.reduction == "mean": return values.sum(dim=-1) / self.total / self.num_estimators return values