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symmetric_mean_absolute_percentage_error.py
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symmetric_mean_absolute_percentage_error.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, Callable, Optional
import torch
from torch import Tensor, tensor
from torchmetrics.functional.regression.symmetric_mean_absolute_percentage_error import (
_symmetric_mean_absolute_percentage_error_compute,
_symmetric_mean_absolute_percentage_error_update,
)
from torchmetrics.metric import Metric
class SymmetricMeanAbsolutePercentageError(Metric):
r"""
Computes symmetric mean absolute percentage error (`SMAPE`_).
.. math:: \text{SMAPE} = \frac{2}{n}\sum_1^n\frac{max(| y_i - \hat{y_i} |}{| y_i | + | \hat{y_i} |, \epsilon)}
Where :math:`y` is a tensor of target values, and :math:`\hat{y}` is a tensor of predictions.
Args:
compute_on_step:
Forward only calls ``update()`` and return None if this is set to False.
dist_sync_on_step:
Synchronize metric state across processes at each ``forward()`` before returning the value at the step.
process_group:
Specify the process group on which synchronization is called. default: None (which selects the entire world)
Note:
The epsilon value is taken from `scikit-learn's implementation of SMAPE`_.
Note:
SMAPE output is a non-negative floating point between 0 and 1. Best result is 0.0 .
Example:
>>> from torchmetrics import SymmetricMeanAbsolutePercentageError
>>> target = torch.tensor([1, 10, 1e6])
>>> preds = torch.tensor([0.9, 15, 1.2e6])
>>> smape = SymmetricMeanAbsolutePercentageError()
>>> smape(preds, target)
tensor(0.2290)
"""
sum_abs_per_error: Tensor
total: Tensor
def __init__(
self,
compute_on_step: bool = True,
dist_sync_on_step: bool = False,
process_group: Optional[Any] = None,
dist_sync_fn: Callable = None,
) -> None:
super().__init__(
compute_on_step=compute_on_step,
dist_sync_on_step=dist_sync_on_step,
process_group=process_group,
dist_sync_fn=dist_sync_fn,
)
self.add_state("sum_abs_per_error", default=tensor(0.0), dist_reduce_fx="sum")
self.add_state("total", default=tensor(0.0), dist_reduce_fx="sum")
def update(self, preds: Tensor, target: Tensor) -> None: # type: ignore
"""Update state with predictions and targets.
Args:
preds: Predictions from model
target: Ground truth values
"""
sum_abs_per_error, num_obs = _symmetric_mean_absolute_percentage_error_update(preds, target)
self.sum_abs_per_error += sum_abs_per_error
self.total += num_obs
def compute(self) -> Tensor:
"""Computes mean absolute percentage error over state."""
return _symmetric_mean_absolute_percentage_error_compute(self.sum_abs_per_error, self.total)
@property
def is_differentiable(self) -> bool:
return True