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paddlepaddle--paddle/python/paddle/nn/initializer/xavier.py
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# Copyright (c) 2020 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
import math
import paddle
from paddle import _C_ops
from ...base import core, framework, unique_name
from ...base.data_feeder import check_variable_and_dtype
from ...base.framework import (
_current_expected_place,
in_dygraph_mode,
in_pir_mode,
)
from .initializer import Initializer
__all__ = []
class XavierInitializer(Initializer):
r"""
This class implements the Xavier weight initializer from the paper
`Understanding the difficulty of training deep feedforward neural
networks <http://proceedings.mlr.press/v9/glorot10a/glorot10a.pdf>`_
by Xavier Glorot and Yoshua Bengio.
This initializer is designed to keep the scale of the gradients
approximately same in all the layers. In case of Uniform distribution,
the range is [-x, x], where
.. math::
x = gain \times \sqrt{\\frac{6.0}{fan\_in + fan\_out}}
In case of Normal distribution, the mean is 0 and the standard deviation
is
.. math::
gain \times \sqrt{\\frac{2.0}{fan\_in + fan\_out}}
Args:
uniform (bool, optional): whether to use uniform ,if False use normal distribution. Default is True.
fan_in (float|None, optional): fan_in for Xavier initialization. If None, it is
inferred from the variable. Default is None.
fan_out (float|None, optional): fan_out for Xavier initialization. If None, it is
inferred from the variable. Default is None.
seed (int, optional): Random seed. Default is 0.
gain (float, optional): Scaling Tensor. Default is 1.0.
Note:
It is recommended to set fan_in and fan_out to None for most cases.
"""
def __init__(
self,
uniform: bool = True,
fan_in: float | None = None,
fan_out: float | None = None,
seed: int = 0,
gain: float = 1.0,
) -> None:
assert uniform is not None
assert seed is not None
super().__init__()
self._uniform = uniform
self._fan_in = fan_in
self._fan_out = fan_out
self._seed = seed
self._gain = gain
def forward(
self, var: paddle.Tensor, block: paddle.pir.Block | None = None
) -> paddle.Tensor | None:
"""Initialize the input tensor with Xavier initialization.
Args:
var(Tensor): Tensor that needs to be initialized.
block(Block|None, optional): The block in which initialization ops
should be added. Used in static graph only, default None.
Returns:
The initialization op
"""
block = self._check_block(block)
assert isinstance(block, (framework.Block, paddle.pir.Block))
if not isinstance(var, paddle.pir.core.ParameterMeta):
check_variable_and_dtype(
var,
"Out",
["uint16", "float16", "float32", "float64"],
"xavier_init",
)
f_in, f_out = self._compute_fans(var)
# If fan_in and fan_out are passed, use them
fan_in = f_in if self._fan_in is None else self._fan_in
fan_out = f_out if self._fan_out is None else self._fan_out
if self._seed == 0:
self._seed = block.program.random_seed
out_var_shape = (
var._local_shape
if (isinstance(var, framework.EagerParamBase) and var.is_dist())
else var.shape
)
# to be compatible of fp16 initializers
origin_dtype = var.dtype
if origin_dtype == core.VarDesc.VarType.FP16 or (
origin_dtype == core.VarDesc.VarType.BF16 and not self._uniform
):
out_dtype = core.VarDesc.VarType.FP32
out_var = block.create_var(
name=unique_name.generate(
".".join(['xavier_init', var.name, 'tmp'])
),
shape=out_var_shape,
dtype=out_dtype,
type=core.VarDesc.VarType.DENSE_TENSOR,
persistable=False,
)
elif (
origin_dtype in (core.DataType.FLOAT16, core.DataType.BFLOAT16)
and not self._uniform
):
out_dtype = core.DataType.FLOAT32
out_var = var
else:
out_dtype = origin_dtype
out_var = var
if in_dygraph_mode():
if self._uniform:
if 0 in [fan_in, fan_out]:
limit = 0.0
else:
limit = self._gain * math.sqrt(
6.0 / float(fan_in + fan_out)
)
out_var = _C_ops.uniform(
out_var_shape,
out_dtype,
-limit,
limit,
self._seed,
_current_expected_place(),
)
else:
if 0 in [fan_in, fan_out]:
std = 0.0
else:
std = self._gain * math.sqrt(2.0 / float(fan_in + fan_out))
place = _current_expected_place()
out_var = _C_ops.gaussian(
out_var_shape,
0.0,
std,
self._seed,
out_dtype,
place,
)
if origin_dtype == core.VarDesc.VarType.FP16 or (
origin_dtype
in [
core.VarDesc.VarType.BF16,
core.DataType.FLOAT16,
core.DataType.BFLOAT16,
]
and not self._uniform
):
out_var = _C_ops.cast(out_var, origin_dtype)
if isinstance(var, framework.EagerParamBase) and var.is_dist():
# lazy init for dist tensor
out_var = (
paddle.distributed.auto_parallel.api.dtensor_from_local(
out_var, var.process_mesh, var.placements
)
)
out_var._share_underline_tensor_to(var)
return None
elif in_pir_mode():
if self._uniform:
if 0 in [fan_in, fan_out]:
limit = 0.0
else:
limit = self._gain * math.sqrt(
6.0 / float(fan_in + fan_out)
)
out_var = paddle._pir_ops.uniform(
out_var.shape,
out_dtype,
-limit,
limit,
self._seed,
_current_expected_place(),
)
else:
if 0 in [fan_in, fan_out]:
std = 0.0
else:
std = self._gain * math.sqrt(2.0 / float(fan_in + fan_out))
out_var = _C_ops.gaussian(
out_var.shape,
0.0,
std,
self._seed,
out_dtype,
_current_expected_place(),
)
if (
origin_dtype in (core.DataType.FLOAT16, core.DataType.BFLOAT16)
and not self._uniform
):
return _C_ops.cast(out_var, origin_dtype)
return out_var
else:
if self._uniform:
if 0 in [fan_in, fan_out]:
limit = 0.0
else:
limit = self._gain * math.sqrt(
6.0 / float(fan_in + fan_out)
)
op = block.append_op(
type="uniform_random",
inputs={},
outputs={"Out": out_var},
attrs={
"shape": out_var.shape,
"dtype": out_dtype,
"min": -limit,
"max": limit,
"seed": self._seed,
},
stop_gradient=True,
)
else:
if 0 in [fan_in, fan_out]:
std = 0.0
else:
std = self._gain * math.sqrt(2.0 / float(fan_in + fan_out))
op = block.append_op(
type="gaussian_random",
outputs={"Out": out_var},
attrs={
"shape": out_var.shape,
"dtype": out_var.dtype,
"mean": 0.0,
"std": std,
"seed": self._seed,
},
stop_gradient=True,
)
if origin_dtype == core.VarDesc.VarType.FP16 or (
origin_dtype == core.VarDesc.VarType.BF16 and not self._uniform
):
block.append_op(
type="cast",
inputs={"X": out_var},
outputs={"Out": var},
attrs={
"in_dtype": out_var.dtype,
"out_dtype": origin_dtype,
},
)
var.op = op
return op
class XavierNormal(XavierInitializer):
r"""
This class implements the Xavier weight initializer from the paper
`Understanding the difficulty of training deep feedforward neural
networks <http://proceedings.mlr.press/v9/glorot10a/glorot10a.pdf>`_
by Xavier Glorot and Yoshua Bengio, using a normal distribution whose mean is :math:`0` and standard deviation is
.. math::
gain \times \sqrt{\frac{2.0}{fan\_in + fan\_out}}.
Args:
fan_in (float|None, optional): fan_in for Xavier initialization, which is
inferred from the Tensor. Default is None.
fan_out (float|None, optional): fan_out for Xavier initialization, which is
inferred from the Tensor. Default is None.
gain (float, optional): Scaling Tensor. Default is 1.0.
name (str|None, optional): For details, please refer to :ref:`api_guide_Name`. Generally, no setting is required. Default: None.
Returns:
A parameter initialized by Xavier weight, using a normal distribution.
Examples:
.. code-block:: pycon
>>> import paddle
>>> paddle.seed(1)
>>> data = paddle.ones(shape=[3, 1, 2], dtype='float32')
>>> weight_attr = paddle.framework.ParamAttr(
... name="linear_weight",
... initializer=paddle.nn.initializer.XavierNormal(),
... )
>>> bias_attr = paddle.framework.ParamAttr(
... name="linear_bias",
... initializer=paddle.nn.initializer.XavierNormal(),
... )
>>> linear = paddle.nn.Linear(2, 2, weight_attr=weight_attr, bias_attr=bias_attr)
>>> print(linear.weight)
Parameter containing:
Tensor(shape=[2, 2], dtype=float32, place=Place(cpu), stop_gradient=False,
[[-0.21607460, 0.08382989],
[ 0.29147008, -0.07049121]])
>>> print(linear.bias)
Parameter containing:
Tensor(shape=[2], dtype=float32, place=Place(cpu), stop_gradient=False,
[1.06076419, 0.87684733])
>>> res = linear(data)
>>> print(res)
Tensor(shape=[3, 1, 2], dtype=float32, place=Place(cpu), stop_gradient=False,
[[[1.13615966, 0.89018601]],
[[1.13615966, 0.89018601]],
[[1.13615966, 0.89018601]]])
"""
def __init__(
self,
fan_in: float | None = None,
fan_out: float | None = None,
gain: float = 1.0,
name: str | None = None,
) -> None:
super().__init__(
uniform=False, fan_in=fan_in, fan_out=fan_out, seed=0, gain=gain
)
class XavierUniform(XavierInitializer):
r"""
This class implements the Xavier weight initializer from the paper
`Understanding the difficulty of training deep feedforward neural
networks <http://proceedings.mlr.press/v9/glorot10a/glorot10a.pdf>`_
by Xavier Glorot and Yoshua Bengio.
This initializer is designed to keep the scale of the gradients
approximately same in all the layers. In case of Uniform distribution,
the range is :math:`[-x,x]`, where
.. math::
x = gain \times \sqrt{\frac{6.0}{fan\_in + fan\_out}}.
Args:
fan_in (float|None, optional): fan_in for Xavier initialization, which is
inferred from the Tensor. Default is None.
fan_out (float|None, optional): fan_out for Xavier initialization, which is
inferred from the Tensor. Default is None.
gain (float, optional): Scaling Tensor. Default is 1.0.
name (str|None, optional): For details, please refer to :ref:`api_guide_Name`. Generally, no setting is required. Default: None.
Returns:
A parameter initialized by Xavier weight, using a uniform distribution.
Examples:
.. code-block:: pycon
>>> import paddle
>>> paddle.seed(1)
>>> data = paddle.ones(shape=[3, 1, 2], dtype='float32')
>>> weight_attr = paddle.framework.ParamAttr(
... name="linear_weight",
... initializer=paddle.nn.initializer.XavierUniform(),
... )
>>> bias_attr = paddle.framework.ParamAttr(
... name="linear_bias",
... initializer=paddle.nn.initializer.XavierUniform(),
... )
>>> linear = paddle.nn.Linear(2, 2, weight_attr=weight_attr, bias_attr=bias_attr)
>>> print(linear.weight)
Parameter containing:
Tensor(shape=[2, 2], dtype=float32, place=Place(cpu), stop_gradient=False,
[[-1.18095720, 0.64892638],
[ 0.43125069, -1.11156428]])
>>> print(linear.bias)
Parameter containing:
Tensor(shape=[2], dtype=float32, place=Place(cpu), stop_gradient=False,
[-0.27524316, 1.13808715])
>>> res = linear(data)
>>> print(res)
Tensor(shape=[3, 1, 2], dtype=float32, place=Place(cpu), stop_gradient=False,
[[[-1.02494967, 0.67544925]],
[[-1.02494967, 0.67544925]],
[[-1.02494967, 0.67544925]]])
"""
def __init__(
self,
fan_in: float | None = None,
fan_out: float | None = None,
gain: float = 1.0,
name: str | None = None,
) -> None:
super().__init__(
uniform=True, fan_in=fan_in, fan_out=fan_out, seed=0, gain=gain
)