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import numpy as np
import torch
import torch.nn as nn
def quantize(x, scale, zero, maxq):
q = torch.clamp(torch.round(x / scale) + zero, 0, maxq)
return scale * (q - zero)
class Quantizer(nn.Module):
def __init__(self, shape=1):
super(Quantizer, self).__init__()
self.register_buffer('maxq', torch.tensor(0))
self.register_buffer('scale', torch.zeros(shape))
self.register_buffer('zero', torch.zeros(shape))
def configure(
self,
bits, perchannel=False, sym=True,
mse=False, norm=2.4, grid=100, maxshrink=.8,
grouprows=1
):
self.maxq = torch.tensor(2 ** bits - 1)
self.perchannel = perchannel
self.sym = sym
self.mse = mse
self.norm = norm
self.grid = grid
self.maxshrink = maxshrink
self.grouprows = grouprows
def find_params(self, x, weight=False):
dev = x.device
self.maxq = self.maxq.to(dev)
shape = x.shape
if self.perchannel:
if weight:
x = x.flatten(1)
if self.grouprows > 1:
x = x.reshape((x.shape[0] // self.grouprows, -1))
else:
if len(shape) == 4:
x = x.permute([1, 0, 2, 3])
x = x.flatten(1)
if len(shape) == 3:
x = x.reshape((-1, shape[-1])).t()
if len(shape) == 2:
x = x.t()
else:
x = x.flatten().unsqueeze(0)
tmp = torch.zeros(x.shape[0], device=dev)
xmin = torch.minimum(x.min(1)[0], tmp)
xmax = torch.maximum(x.max(1)[0], tmp)
if self.sym:
xmax = torch.maximum(torch.abs(xmin), xmax)
tmp = xmin < 0
if torch.any(tmp):
xmin[tmp] = -xmax[tmp]
tmp = (xmin == 0) & (xmax == 0)
xmin[tmp] = -1
xmax[tmp] = +1
self.scale = (xmax - xmin) / self.maxq
if self.sym:
self.zero = torch.full_like(self.scale, (self.maxq + 1) / 2)
else:
self.zero = torch.round(-xmin / self.scale)
if self.mse:
best = torch.full([x.shape[0]], float('inf'), device=dev)
for i in range(int(self.maxshrink * self.grid)):
p = 1 - i / self.grid
xmin1 = p * xmin
xmax1 = p * xmax
scale1 = (xmax1 - xmin1) / self.maxq
zero1 = torch.round(-xmin1 / scale1) if not self.sym else self.zero
q = quantize(x, scale1.unsqueeze(1), zero1.unsqueeze(1), self.maxq)
q -= x
q.abs_()
q.pow_(self.norm)
err = torch.sum(q, 1)
tmp = err < best
if torch.any(tmp):
best[tmp] = err[tmp]
self.scale[tmp] = scale1[tmp]
self.zero[tmp] = zero1[tmp]
if not self.perchannel:
if weight:
tmp = shape[0]
else:
tmp = shape[1] if len(shape) != 3 else shape[2]
self.scale = self.scale.repeat(tmp)
self.zero = self.zero.repeat(tmp)
if weight:
if self.grouprows > 1:
self.scale = self.scale.unsqueeze(1).repeat(1, self.grouprows)
self.zero = self.zero.unsqueeze(1).repeat(1, self.grouprows)
shape = [-1] + [1] * (len(shape) - 1)
self.scale = self.scale.reshape(shape)
self.zero = self.zero.reshape(shape)
return
if len(shape) == 4:
self.scale = self.scale.reshape((1, -1, 1, 1))
self.zero = self.zero.reshape((1, -1, 1, 1))
if len(shape) == 3:
self.scale = self.scale.reshape((1, 1, -1))
self.zero = self.zero.reshape((1, 1, -1))
if len(shape) == 2:
self.scale = self.scale.unsqueeze(0)
self.zero = self.zero.unsqueeze(0)
def quantize(self, x):
if self.ready():
return quantize(x, self.scale, self.zero, self.maxq)
return x
def enabled(self):
return self.maxq > 0
def ready(self):
return torch.all(self.scale != 0)
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