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# Copyright (c) Microsoft Corporation.
# SPDX-License-Identifier: Apache-2.0
# DeepSpeed Team
import torch
import math
from deepspeed.utils import logger
from deepspeed.ops.quantizer import ds_quantizer
TWO_D_PARAMS = 6
class Quantizer(object):
def __init__(self,
q_groups=1,
q_mixed_fp16=False,
q_change_ratio=0.01,
q_type=0,
q_rounding=0,
q_verbose=False,
q_eigenvalue=False,
use_quantizer_kernel=False,
layer_num=0):
self.q_groups = q_groups
self.q_mixed_fp16 = q_mixed_fp16
self.q_change_ratio = q_change_ratio
self.q_type = q_type
self.qsteps = 0
self.quantize_real_ratio = 1.000
self.q_verbose = q_verbose
self.q_eigenvalue = q_eigenvalue
self.use_quantizer_kernel = use_quantizer_kernel
self.q_rounding = q_rounding
self.layer_num = layer_num
def any_precision_switch(self):
# Temporary disabled functionality
if self.layer_num == 0:
return True
result = False
for index in range(self.layer_num):
if self.q_start_bits[index] != self.q_target_bits:
next_step = self.qsteps + (TWO_D_PARAMS * (self.layer_num if self.layer_num != 0 else 1))
if next_step >= self.q_period[index]:
result = True
return result
def quantize(self, parameter_group, overflow, eigenvalue_enabled, block_eigenvalue={}):
if overflow and not eigenvalue_enabled:
return
self.step()
self.update_fp16_ratio()
for i in range(len(parameter_group)):
for p in parameter_group[i]:
if len(p.size()) > 1 and hasattr(p, "start_bits") and p.start_bits:
param_id = id(p)
if block_eigenvalue is None:
eigenvalue, layer_id = None, 0
else:
eigenvalue, layer_id = block_eigenvalue[param_id] if param_id in block_eigenvalue else (None,
0)
if eigenvalue is not None:
factor = 1 + math.floor(eigenvalue * 4)
p.data = self.compute_quantization(p.data, layer_id, factor)
else:
p.data = self.compute_quantization(p, layer_id)
def step(self):
self.qsteps += 1
def quantize_highbit(self, inputs, num_bits):
q_range = 2**num_bits
input_flat = inputs.reshape(self.q_groups, -1)
g_min = input_flat.amin(dim=-1, keepdim=True)
g_max = input_flat.amax(dim=-1, keepdim=True)
# Random number generator (Uniform)
if self.q_rounding == 'nearest':
p = 0.
else:
p = input_flat.new(input_flat.shape).uniform_(-0.5, 0.5)
if self.q_type == 'symmetric':
scale = 2 * torch.max(torch.abs(g_min), torch.abs(g_max)) / q_range
zero_point = 0.
input_flat = (input_flat / scale + p).round().clamp(-(q_range >> 1), (q_range >> 1) - 1) * scale
elif self.q_type == 'asymmetric':
scale = (g_max - g_min) / q_range
zero_point = (g_min / scale).round() * scale
input_flat = ((input_flat - zero_point) / scale + p).round().clamp(0, (q_range - 1)) * scale + zero_point
output = input_flat.reshape(inputs.shape).contiguous()
return output
def quantize_tenary(self, inputs):
input_flat = inputs.reshape(self.q_groups, -1)
n = input_flat.shape[1]
m = input_flat.norm(p=1, dim=1).div(n)
thres = (0.7 * m).view(-1, 1) #.expand_as(input_flat)
pos = (input_flat > thres).type(inputs.type())
neg = (input_flat < -thres).type(inputs.type())
mask = (input_flat.abs() > thres).type(inputs.type())
alpha = ((mask * input_flat).abs().sum(dim=1) / mask.sum(dim=1)).view(-1, 1)
output = alpha * pos - alpha * neg
output = output.reshape(inputs.shape).contiguous()
return output
def quantize_binary(self, inputs):
input_flat = inputs.reshape(self.q_groups, -1)
n = input_flat.shape[1]
m = input_flat.norm(p=1, dim=1, keepdim=True).div(n)
output = input_flat.sign().mul(m)
output = output.reshape(inputs.shape).contiguous()
return output
def mixed_fp16_quantize(self, input, input_q, index):
if self.q_mixed_fp16 and self.q_start_bits[index] >= (self.q_target_bits - 1):
input_q = input * self.quantize_real_ratio + (1 - self.quantize_real_ratio) * input_q
return input_q
return input_q
def compute_quantization(self, input, index=0, factor=1):
# fixing the quantization bits based on the training steps
# when reducing 1 bit at each period, we increase the period
# to go slowly toward the target quantization bits
# the period and starting bit can be configured
if input.start_bits != input.target_bits:
if self.qsteps >= input.q_period:
self.quantize_real_ratio = 1.0
input.q_period <<= 1
input.q_period *= factor
input.start_bits -= 1
if self.q_verbose:
logger.info(
f'Quantization settings: current bit-precision = {input.start_bits}, step = {self.qsteps}, quantization period = {input.q_period}, index = {index}'
)
assert (input.start_bits >= input.target_bits), \
'Quantization bit is lower than target precision bits!'
if self.use_quantizer_kernel:
if input.start_bits <= 2:
raise ValueError('Quantization bit is too low, please do it without quantization kernel!')
input_q = ds_quantizer(input.data.clone(),
self.q_groups,
input.start_bits,
asym=False if self.q_type == 'symmetric' else True,
sr=False if self.q_rounding == 'nearest_neighbor' else True)
else:
if input.start_bits >= 3:
input_flat = self.quantize_highbit(input.data, input.start_bits)
elif input.start_bits == 2:
assert self.q_type == 'symmetric', 'Quantization type is not symmetric!'
assert self.q_rounding == 'nearest', 'Quantization rounding is not nearest_neighbor!'
input_flat = self.quantize_tenary(input.data)
elif input.start_bits == 1:
assert self.q_type == 'symmetric', 'Quantization type is not symmetric!'
assert self.q_rounding == 'nearest', 'Quantization rounding is not nearest_neighbor!'
input_flat = self.quantize_binary(input.data)
if self.use_quantizer_kernel:
return self.mixed_fp16_quantize(input.data, input_q, index)
else:
if self.q_mixed_fp16 and input.start_bits >= input.target_bits - 1:
input_flat = self.quantize_real_ratio * input.data + \
(1 - self.quantize_real_ratio) * input_flat
return input_flat
def update_fp16_ratio(self):
if self.q_mixed_fp16:
if self.quantize_real_ratio > 0:
self.quantize_real_ratio -= self.q_change_ratio
else:
self.quantize_real_ratio = 0.000
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