Shortcuts

Source code for ignite.metrics.precision

import warnings
from typing import Callable, Sequence, Union, cast

import torch

import ignite.distributed as idist
from ignite.exceptions import NotComputableError
from ignite.metrics.accuracy import _BaseClassification
from ignite.metrics.metric import reinit__is_reduced
from ignite.utils import to_onehot

__all__ = ["Precision"]


class _BasePrecisionRecall(_BaseClassification):
    def __init__(
        self,
        output_transform: Callable = lambda x: x,
        average: bool = False,
        is_multilabel: bool = False,
        device: Union[str, torch.device] = torch.device("cpu"),
    ):
        if idist.get_world_size() > 1:
            if (not average) and is_multilabel:
                warnings.warn(
                    "Precision/Recall metrics do not work in distributed setting when average=False "
                    "and is_multilabel=True. Results are not reduced across computing devices. Computed result "
                    "corresponds to the local rank's (single process) result.",
                    RuntimeWarning,
                )

        self._average = average
        self.eps = 1e-20
        super(_BasePrecisionRecall, self).__init__(
            output_transform=output_transform, is_multilabel=is_multilabel, device=device
        )

    @reinit__is_reduced
    def reset(self) -> None:
        self._true_positives = 0  # type: Union[int, torch.Tensor]
        self._positives = 0  # type: Union[int, torch.Tensor]

        if self._is_multilabel:
            init_value = 0.0 if self._average else []
            self._true_positives = torch.tensor(init_value, dtype=torch.float64, device=self._device)
            self._positives = torch.tensor(init_value, dtype=torch.float64, device=self._device)

        super(_BasePrecisionRecall, self).reset()

    def compute(self) -> Union[torch.Tensor, float]:
        is_scalar = not isinstance(self._positives, torch.Tensor) or self._positives.ndim == 0
        if is_scalar and self._positives == 0:
            raise NotComputableError(
                f"{self.__class__.__name__} must have at least one example before it can be computed."
            )

        if not (self._type == "multilabel" and not self._average):
            if not self._is_reduced:
                self._true_positives = idist.all_reduce(self._true_positives)  # type: ignore[assignment]
                self._positives = idist.all_reduce(self._positives)  # type: ignore[assignment]
                self._is_reduced = True  # type: bool

        result = self._true_positives / (self._positives + self.eps)

        if self._average:
            return cast(torch.Tensor, result).mean().item()
        else:
            return result


[docs]class Precision(_BasePrecisionRecall): r"""Calculates precision for binary and multiclass data. .. math:: \text{Precision} = \frac{ TP }{ TP + FP } where :math:`\text{TP}` is true positives and :math:`\text{FP}` is false positives. - ``update`` must receive output of the form ``(y_pred, y)`` or ``{'y_pred': y_pred, 'y': y}``. - `y_pred` must be in the following shape (batch_size, num_categories, ...) or (batch_size, ...). - `y` must be in the following shape (batch_size, ...). In binary and multilabel cases, the elements of `y` and `y_pred` should have 0 or 1 values. Thresholding of predictions can be done as below: .. code-block:: python def thresholded_output_transform(output): y_pred, y = output y_pred = torch.round(y_pred) return y_pred, y precision = Precision(output_transform=thresholded_output_transform) In multilabel cases, average parameter should be True. However, if user would like to compute F1 metric, for example, average parameter should be False. This can be done as shown below: .. code-block:: python precision = Precision(average=False, is_multilabel=True) recall = Recall(average=False, is_multilabel=True) F1 = precision * recall * 2 / (precision + recall + 1e-20) F1 = MetricsLambda(lambda t: torch.mean(t).item(), F1) .. warning:: In multilabel cases, if average is False, current implementation stores all input data (output and target) in as tensors before computing a metric. This can potentially lead to a memory error if the input data is larger than available RAM. .. warning:: In multilabel cases, if average is False, current implementation does not work with distributed computations. Results are not reduced across the GPUs. Computed result corresponds to the local rank's (single GPU) result. Args: output_transform (callable, optional): a callable that is used to transform the :class:`~ignite.engine.engine.Engine`'s ``process_function``'s output into the form expected by the metric. This can be useful if, for example, you have a multi-output model and you want to compute the metric with respect to one of the outputs. average (bool, optional): if True, precision is computed as the unweighted average (across all classes in multiclass case), otherwise, returns a tensor with the precision (for each class in multiclass case). is_multilabel (bool, optional) flag to use in multilabel case. By default, value is False. If True, average parameter should be True and the average is computed across samples, instead of classes. device (str or torch.device): specifies which device updates are accumulated on. Setting the metric's device to be the same as your ``update`` arguments ensures the ``update`` method is non-blocking. By default, CPU. """ def __init__( self, output_transform: Callable = lambda x: x, average: bool = False, is_multilabel: bool = False, device: Union[str, torch.device] = torch.device("cpu"), ): super(Precision, self).__init__( output_transform=output_transform, average=average, is_multilabel=is_multilabel, device=device ) @reinit__is_reduced def update(self, output: Sequence[torch.Tensor]) -> None: self._check_shape(output) self._check_type(output) y_pred, y = output[0].detach(), output[1].detach() if self._type == "binary": y_pred = y_pred.view(-1) y = y.view(-1) elif self._type == "multiclass": num_classes = y_pred.size(1) if y.max() + 1 > num_classes: raise ValueError( f"y_pred contains less classes than y. Number of predicted classes is {num_classes}" f" and element in y has invalid class = {y.max().item() + 1}." ) y = to_onehot(y.view(-1), num_classes=num_classes) indices = torch.argmax(y_pred, dim=1).view(-1) y_pred = to_onehot(indices, num_classes=num_classes) elif self._type == "multilabel": # if y, y_pred shape is (N, C, ...) -> (C, N x ...) num_classes = y_pred.size(1) y_pred = torch.transpose(y_pred, 1, 0).reshape(num_classes, -1) y = torch.transpose(y, 1, 0).reshape(num_classes, -1) # Convert from int cuda/cpu to double on self._device y_pred = y_pred.to(dtype=torch.float64, device=self._device) y = y.to(dtype=torch.float64, device=self._device) correct = y * y_pred all_positives = y_pred.sum(dim=0) if correct.sum() == 0: true_positives = torch.zeros_like(all_positives) else: true_positives = correct.sum(dim=0) if self._type == "multilabel": if not self._average: self._true_positives = torch.cat([self._true_positives, true_positives], dim=0) # type: torch.Tensor self._positives = torch.cat([self._positives, all_positives], dim=0) # type: torch.Tensor else: self._true_positives += torch.sum(true_positives / (all_positives + self.eps)) self._positives += len(all_positives) else: self._true_positives += true_positives self._positives += all_positives

© Copyright 2023, PyTorch-Ignite Contributors. Last updated on 02/03/2023, 2:13:25 PM.

Built with Sphinx using a theme provided by Read the Docs.