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paddlepaddle--paddle/python/paddle/incubate/nn/loss.py
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2026-07-13 12:40:42 +08:00

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# Copyright (c) 2019 PaddlePaddle Authors. All Rights Reserved.
#
# 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 __future__ import annotations
from typing import TYPE_CHECKING
from paddle import _C_ops
from paddle.base.data_feeder import check_variable_and_dtype
from paddle.base.layer_helper import LayerHelper
from paddle.framework import in_dynamic_or_pir_mode
if TYPE_CHECKING:
from typing import Literal, TypeAlias
from paddle import Tensor
_ReduceModeStringLiteral: TypeAlias = Literal['mean', 'sum', 'none']
_ReduceModeNumberLiteral: TypeAlias = Literal[0, 1, 2]
_ReduceMode: TypeAlias = _ReduceModeStringLiteral | _ReduceModeNumberLiteral
def identity_loss(x: Tensor, reduction: _ReduceMode = "none") -> Tensor:
r"""Marks a tensor as being part of the loss calculation for IPU.
This operator is used to handle on the (final) loss of a model so that
it is used as the start of backpropagation.
When `reduction` is `none`, return raw `Out`.
When `reduction` is `mean`, return
.. math::
Out = MEAN(Out)
When `reduction` is `sum`, return
.. math::
Out = SUM(Out)
Parameters:
x (Variable): The input tensor. The shapes is [N, *], where N is batch size and `*` means any number of
additional dimensions. It's data type should be float32, float64 on CPU and float16, float32 on IPU.
reduction(str|int, optional): Reduce the loss output. Supported string values are: 'sum', 'mean', 'none'
the corresponding int values are 0, 1, 2 respectively. The default value is "none".
Returns:
Variable: The loss ``Tensor`` with the specified reduction applied.
Examples:
.. code-block:: pycon
>>> import paddle
>>> paddle.enable_static()
>>> loss = paddle.static.data(name="loss", shape=[-1, 1], dtype="float32")
>>> out = paddle.incubate.identity_loss(loss, reduction=1)
"""
if isinstance(reduction, str):
reduction = {"sum": 0, "mean": 1, "none": 2}.get(reduction.lower())
if reduction is None:
raise TypeError("Unsupported reduction type.")
if in_dynamic_or_pir_mode():
return _C_ops.identity_loss(x, reduction)
check_variable_and_dtype(x, 'x', ['float32', 'float64'], "identity_loss")
attrs = {'reduction': reduction}
helper = LayerHelper('identity_loss', **locals())
dtype = helper.input_dtype(input_param_name='x')
out = helper.create_variable_for_type_inference(dtype)
helper.append_op(
type="identity_loss", inputs={"X": x}, outputs={"Out": out}, attrs=attrs
)
return out