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

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Python

# Copyright (c) 2022 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.
import math
import paddle
from paddle.autograd import PyLayer
from paddle.framework import ParamAttr
from paddle.nn.initializer import Constant
from paddle.utils import unique_name
from ..layer.layers import Layer
def round(x):
sign = paddle.sign(x)
x = sign * paddle.floor(paddle.abs(x) + 0.5)
return x
class LsqFunc(PyLayer):
@staticmethod
def forward(ctx, weight, alpha, g, Qn, Qp, per_channel=False, quant_axis=0):
ctx.save_for_backward(weight, alpha)
ctx.other = g, Qn, Qp, per_channel, quant_axis
if per_channel:
sizes = weight.shape
weight = weight.reshape((weight.shape[quant_axis], -1))
weight = weight.transpose((1, 0))
alpha = paddle.broadcast_to(alpha, weight.shape)
quant_w = round(paddle.divide(weight, alpha)).clip(Qn, Qp)
quant_w = quant_w * alpha
quant_w = quant_w.transpose((1, 0))
quant_w = quant_w.reshape(sizes)
else:
quant_w = round(paddle.divide(weight, alpha)).clip(Qn, Qp)
quant_w = quant_w * alpha
return quant_w
@staticmethod
def backward(ctx, grad_weight):
weight, alpha = ctx.saved_tensor()
g, Qn, Qp, per_channel, quant_axis = ctx.other
if per_channel:
sizes = weight.shape
weight = weight.reshape((weight.shape[quant_axis], -1))
weight = weight.transpose((1, 0))
alpha = paddle.broadcast_to(alpha, weight.shape)
q_w = paddle.divide(weight, alpha)
q_w = q_w.transpose((1, 0))
q_w = q_w.reshape(sizes)
else:
q_w = paddle.divide(weight, alpha)
lower_flag = paddle.cast((q_w < Qn), 'float32')
upper_flag = paddle.cast((q_w > Qp), 'float32')
middle_flag = 1.0 - lower_flag - upper_flag
if per_channel:
grad_alpha = (
(
lower_flag * Qn
+ upper_flag * Qp
+ middle_flag * round(q_w)
- middle_flag * q_w
)
* grad_weight
* g
)
grad_alpha = grad_alpha.reshape(
(grad_alpha.shape[quant_axis], -1)
).sum(axis=1)
else:
grad_alpha = (
(
(
lower_flag * Qn
+ upper_flag * Qp
+ middle_flag * round(q_w)
- middle_flag * q_w
)
* grad_weight
* g
)
.sum()
.unsqueeze(axis=0)[0]
)
grad_weight = middle_flag * grad_weight
return grad_weight, grad_alpha
class LsqPlusActFunc(PyLayer):
@staticmethod
def forward(ctx, x, alpha, beta, g, Qn, Qp):
ctx.save_for_backward(x, alpha, beta)
ctx.other = g, Qn, Qp
quant_x = round(paddle.divide((x - beta), alpha)).clip(Qn, Qp)
return quant_x * alpha + beta
@staticmethod
def backward(ctx, grad_x):
x, alpha, beta = ctx.saved_tensor()
g, Qn, Qp = ctx.other
q_x = (x - beta) / alpha
lower_flag = paddle.cast((q_x < Qn), 'float32')
upper_flag = paddle.cast((q_x > Qp), 'float32')
middle_flag = 1.0 - lower_flag - upper_flag
grad_alpha = (
(
(
lower_flag * Qn
+ upper_flag * Qp
+ middle_flag * round(q_x)
- middle_flag * q_x
)
* grad_x
* g
)
.sum()
.unsqueeze(axis=0)[0]
)
grad_beta = (
((lower_flag + upper_flag) * grad_x * g).sum().unsqueeze(axis=0)[0]
)
grad_x = middle_flag * grad_x
return grad_x, grad_alpha, grad_beta
class FakeQuantActLSQPlus(Layer):
def __init__(
self,
quant_bits,
all_positive=False,
symmetric=False,
batch_init=20,
dtype='float32',
name=None,
reduce_type=None,
):
super().__init__()
'''
Args:
quant_bits(int): quantization bit number for weights.
all_positive(bool): whether unsigned or signed quantization, where True for unsigned quantization and False for signed quantization.
symmetric(bool): whether symmetric or asymmetric quantization.
batch_init(int): number of batches that collect Gaussian approximation for the weight distribution in each layer.
dtype(str): data type.
name(str): the name of the weight.
reduce_type(str): the reduce type which is needed when parallel training.
'''
self.bits = quant_bits
self.all_positive = all_positive
self.symmetric = symmetric
self.batch_init = batch_init
self.name = name
self.reduce_type = reduce_type
if self.all_positive:
# unsigned activation
self.Qn = 0
self.Qp = 2**self.bits - 1
else:
# signed activation
self.Qn = -(2 ** (self.bits - 1))
self.Qp = 2 ** (self.bits - 1) - 1
scale_prefix = f"{name}.scale" if name else 'quant_dequant.scale'
self._scale_name = unique_name.generate(scale_prefix)
s_attr = ParamAttr(
name=self._scale_name, initializer=Constant(1.0), trainable=True
)
self.s = self.create_parameter(shape=[], attr=s_attr, dtype='float32')
self.s.stop_gradient = False
if not self.symmetric:
beta_prefix = f"{name}.beta" if name else 'quant_dequant.beta'
self._beta_name = unique_name.generate(beta_prefix)
beta_attr = ParamAttr(
name=self._beta_name, initializer=Constant(0.0), trainable=True
)
self.beta = self.create_parameter(
shape=[], attr=beta_attr, dtype='float32'
)
self.beta.stop_gradient = False
self.init_state = 0
def forward(self, activation):
if self.reduce_type == "max":
paddle.distributed.all_reduce(
self.s, op=paddle.distributed.ReduceOp.MAX
)
if not self.symmetric and self.reduce_type == "max":
paddle.distributed.all_reduce(
self.beta, op=paddle.distributed.ReduceOp.MAX
)
if self.init_state == 0:
self.g = paddle.to_tensor(
1.0 / math.sqrt(activation.numel() * self.Qp)
)
min_a = paddle.min(activation.detach())
max_a = paddle.max(activation.detach())
self.s.set_value((max_a - min_a) / (self.Qp - self.Qn))
if not self.symmetric:
self.beta.set_value(min_a - self.s * self.Qn)
self.init_state += 1
elif self.init_state < self.batch_init:
min_a = paddle.min(activation.detach())
max_a = paddle.max(activation.detach())
self.s.set_value(
self.s * 0.9 + 0.1 * (max_a - min_a) / (self.Qp - self.Qn)
)
if not self.symmetric:
self.beta.set_value(
self.s * 0.9 + 0.1 * (min_a - self.s * self.Qn)
)
self.init_state += 1
else:
self.init_state += 1
activation.stop_gradient = False
if not self.symmetric:
q_a = LsqPlusActFunc.apply(
activation, self.s, self.beta, self.g, self.Qn, self.Qp
)
else:
q_a = LsqFunc.apply(
activation, self.s, self.g, self.Qn, self.Qp, per_channel=False
)
return q_a
class FakeQuantWeightLSQPlus(Layer):
def __init__(
self,
quant_bits,
all_positive=False,
per_channel=False,
batch_init=20,
channel_num=None,
quant_linear=False,
dtype='float32',
name=None,
reduce_type=None,
):
super().__init__()
'''
Args:
quant_bits(int): quantization bit number for weights.
all_positive(bool): whether unsigned or signed quantization, where True for unsigned quantization and False for signed quantization.
per_channel(bool): whether layer-wise or channel-wise quantization, where True for layer-wise quantization and False for channel-wise quantization.
batch_init(int): number of batches that collect Gaussian approximation for the weight distribution in each layer.
channel_num(int): the channel number of the weight which is needed when per_channel is True.
quant_linear(bool): whether the weight is from Linear.
dtype(str): data type.
name(str): the name of the weight.
reduce_type(str): the reduce type which is needed when parallel training.
'''
self.bits = quant_bits
self.all_positive = all_positive
self.per_channel = per_channel
self.quant_linear = quant_linear
self.batch_init = batch_init
self.name = name
self.quant_axis = 1 if quant_linear else 0
self.collect_axis = 0 if quant_linear else 1
self.reduce_type = reduce_type
if self.all_positive:
# unsigned weight
self.Qn = 0
self.Qp = 2**self.bits - 1
else:
# signed weight
self.Qn = -(2 ** (self.bits - 1))
self.Qp = 2 ** (self.bits - 1) - 1
self.init_state = 0
scale_prefix = f"{name}.scale" if name else 'quant_dequant.scale'
self._scale_name = unique_name.generate(scale_prefix)
s_attr = ParamAttr(
name=self._scale_name, initializer=Constant(1.0), trainable=True
)
self.s = self.create_parameter(
shape=[channel_num], attr=s_attr, dtype=dtype
)
self.s.stop_gradient = False
def forward(self, weight):
if self.reduce_type == "max":
paddle.distributed.all_reduce(
self.s, op=paddle.distributed.ReduceOp.MAX
)
if self.init_state == 0:
self.g = paddle.to_tensor(1.0 / math.sqrt(weight.numel() * self.Qp))
self.div = 2**self.bits - 1
if self.per_channel:
weight_tmp = weight.detach().reshape((weight.shape[0], -1))
mean = paddle.mean(weight_tmp, axis=self.collect_axis)
std = paddle.std(weight_tmp, axis=self.collect_axis)
s = paddle.max(
paddle.stack(
[paddle.abs(mean - 3 * std), paddle.abs(mean + 3 * std)]
),
axis=0,
)
self.s.set_value(s / self.div)
else:
mean = paddle.mean(weight.detach())
std = paddle.std(weight.detach())
self.s.set_value(
max(
[paddle.abs(mean - 3 * std), paddle.abs(mean + 3 * std)]
)
/ self.div
)
self.init_state += 1
elif self.init_state < self.batch_init:
self.div = 2**self.bits - 1
if self.per_channel:
weight_tmp = weight.detach().reshape((weight.shape[0], -1))
mean = paddle.mean(weight_tmp, axis=self.collect_axis)
std = paddle.std(weight_tmp, axis=self.collect_axis)
s = paddle.max(
paddle.stack(
[paddle.abs(mean - 3 * std), paddle.abs(mean + 3 * std)]
),
axis=0,
)
self.s.set_value(s * 0.9 + 0.1 * s / self.div)
else:
mean = paddle.mean(weight.detach())
std = paddle.std(weight.detach())
self.s.set_value(
self.s * 0.9
+ 0.1
* max(
[paddle.abs(mean - 3 * std), paddle.abs(mean + 3 * std)]
)
/ self.div
)
self.init_state += 1
elif self.init_state == self.batch_init:
self.init_state += 1
weight.stop_gradient = False
w_q = LsqFunc.apply(
weight,
self.s,
self.g,
self.Qn,
self.Qp,
self.per_channel,
self.quant_axis,
)
return w_q