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1689 lines
65 KiB
1689 lines
65 KiB
"""
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This module implements observers which are used to collect statistics about
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the values observed during calibration (PTQ) or training (QAT).
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"""
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import re
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import warnings
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from abc import ABCMeta, abstractmethod
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from collections import OrderedDict
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from functools import partial
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from typing import Any, List, Tuple, Optional, Dict
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import torch
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import torch.nn as nn
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from torch.ao.quantization.utils import (
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check_min_max_valid, calculate_qmin_qmax, is_per_tensor, is_per_channel, validate_qmin_qmax)
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__all__ = [
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"default_affine_fixed_qparams_observer",
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"default_debug_observer",
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"default_dynamic_quant_observer",
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"default_fixed_qparams_range_0to1_observer",
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"default_fixed_qparams_range_neg1to1_observer",
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"default_float_qparams_observer",
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"default_float_qparams_observer_4bit",
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"default_histogram_observer",
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"default_observer",
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"default_per_channel_weight_observer",
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"default_placeholder_observer",
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"default_reuse_input_observer",
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"default_symmetric_fixed_qparams_observer",
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"default_weight_observer",
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"get_observer_state_dict",
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"load_observer_state_dict",
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"per_channel_weight_observer_range_neg_127_to_127",
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"weight_observer_range_neg_127_to_127",
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"FixedQParamsObserver",
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"HistogramObserver",
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"MinMaxObserver",
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"MovingAverageMinMaxObserver",
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"MovingAveragePerChannelMinMaxObserver",
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"NoopObserver",
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"ObserverBase",
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"PerChannelMinMaxObserver",
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"PlaceholderObserver",
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"RecordingObserver",
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"ReuseInputObserver",
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"UniformQuantizationObserverBase",
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]
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|
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class _PartialWrapper:
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def __init__(self, p):
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self.p = p
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self.callable_args = {}
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def __call__(self, *args, **keywords):
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# call each arg in callable_args and add them partial, then run with keywords
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# skip if arg_name in keywords so its possible to overwrite
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for arg_name in self.callable_args:
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if arg_name not in keywords:
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keywords = {**keywords, arg_name: self.callable_args[arg_name]()}
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return self.p(*args, **keywords)
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def __repr__(self):
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return self.p.__repr__() + self.callable_args.__repr__()
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def with_args(self, **kwargs):
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return _with_args(self, **kwargs)
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def with_callable_args(self, **kwargs):
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result = _PartialWrapper(p=self.p)
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result.callable_args = {**self.callable_args, **kwargs}
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return result
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def _with_args(cls_or_self, **kwargs):
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r"""Wrapper that allows creation of class factories.
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This can be useful when there is a need to create classes with the same
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constructor arguments, but different instances. Can be used in conjunction with
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_callable_args
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Example::
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>>> # xdoctest: +SKIP("Undefined vars")
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>>> Foo.with_args = classmethod(_with_args)
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>>> foo_builder = Foo.with_args(a=3, b=4).with_args(answer=42)
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>>> foo_instance1 = foo_builder()
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>>> foo_instance2 = foo_builder()
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>>> id(foo_instance1) == id(foo_instance2)
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False
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"""
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r = _PartialWrapper(partial(cls_or_self, **kwargs))
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return r
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def _with_callable_args(cls_or_self, **kwargs):
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r"""Wrapper that allows creation of class factories args that need to be
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called at construction time.
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This can be useful when there is a need to create classes with the same
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constructor arguments, but different instances and those arguments should only
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be calculated at construction time. Can be used in conjunction with _with_args
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|
Example::
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>>> # xdoctest: +SKIP("Undefined vars")
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>>> Foo.with_callable_args = classmethod(_with_callable_args)
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>>> Foo.with_args = classmethod(_with_args)
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>>> foo_builder = Foo.with_callable_args(cur_time=get_time_func).with_args(name="dan")
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>>> foo_instance1 = foo_builder()
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>>> # wait 50
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>>> foo_instance2 = foo_builder()
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>>> id(foo_instance1.creation_time) == id(foo_instance2.creation_time)
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False
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"""
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r = _PartialWrapper(partial(cls_or_self))
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return r.with_callable_args(**kwargs)
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ABC: Any = ABCMeta("ABC", (object,), {}) # compatible with Python 2 *and* 3:
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|
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class ObserverBase(ABC, nn.Module):
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r"""Base observer Module.
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Any observer implementation should derive from this class.
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Concrete observers should follow the same API. In forward, they will update
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the statistics of the observed Tensor. And they should provide a
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`calculate_qparams` function that computes the quantization parameters given
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the collected statistics.
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Args:
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dtype: dtype argument to the `quantize` node needed to implement the
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reference model spec.
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is_dynamic: indicator for whether the observer is a placeholder for dynamic quantization
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or static quantization
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"""
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def __init__(self, dtype, is_dynamic=False):
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super().__init__()
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self.dtype = dtype
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self.is_dynamic = is_dynamic
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@abstractmethod
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def forward(self, x):
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pass
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@abstractmethod
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def calculate_qparams(self, **kwargs):
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pass
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with_args = classmethod(_with_args)
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with_callable_args = classmethod(_with_callable_args)
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class UniformQuantizationObserverBase(ObserverBase):
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r"""Common base for all observers using uniform quantization to calculate
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scale and zero_point.
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Args:
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dtype: dtype argument to the `quantize` node needed to implement the
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reference model spec.
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qscheme: Quantization scheme to be used.
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reduce_range: Reduces the range of the quantized data type by 1 bit.
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This is sometimes required to avoid instruction overflow.
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quant_min: Minimum quantization value. If unspecified, it will follow the 8-bit setup.
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quant_max: Maximum quantization value. If unspecified, it will follow the 8-bit setup.
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eps: Epsilon value for float32, Defaults to `torch.finfo(torch.float32).eps`.
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.. warning::
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:attr:`dtype` can only take ``torch.qint8`` or ``torch.quint8``.
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or `torch.int8` or `torch.uint8`
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.. warning::
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:attr:`qscheme` can only take one of the following options:
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- ``torch.per_tensor_affine``
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- ``torch.per_tensor_symmetric``
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- ``torch.per_channel_affine``
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- ``torch.per_channel_symmetric``
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"""
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# Note: the version is shared by all observer types
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#
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# Version 1/None
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# self
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#
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# Version 2 (base class only, does not include child class buffers)
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# self
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# |--- eps : Tensor
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#
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# Version 3
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# for HistogramObserver only, changed the shape of uninitialized
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# min_val and max_val buffers from torch.Size([0]) to torch.Size([])
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# for PerChannelObservers, changed the name of the buffers from min_vals
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# to min_val and from max_vals to max_val.
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_version = 3
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eps: torch.Tensor
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def __init__(
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self,
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dtype=torch.quint8,
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qscheme=torch.per_tensor_affine,
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reduce_range=False,
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quant_min=None,
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quant_max=None,
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factory_kwargs=None,
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eps=torch.finfo(torch.float32).eps,
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is_dynamic=False,
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**kwargs,
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) -> None:
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factory_kwargs = torch.nn.factory_kwargs(factory_kwargs)
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super().__init__(dtype=dtype, is_dynamic=is_dynamic, **kwargs)
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self.qscheme = qscheme
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if reduce_range:
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warnings.warn(
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"Please use quant_min and quant_max to specify the range for observers. \
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reduce_range will be deprecated in a future release of PyTorch."
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)
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self.reduce_range = reduce_range
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self.register_buffer(
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"eps", torch.tensor([eps], **factory_kwargs)
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)
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assert self.qscheme in (
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torch.per_tensor_affine,
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torch.per_tensor_symmetric,
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torch.per_channel_affine,
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torch.per_channel_symmetric,
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torch.per_channel_affine_float_qparams,
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), "Default Observer only works for per_tensor_affine, \
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per_tensor_symmetric, per_channel_affine, \
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per_channel_symmetric and per_channel_float_qparams quantization scheme"
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_ALLOWED_DTYPES = (
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torch.qint8,
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torch.quint8,
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torch.quint4x2,
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torch.qint32,
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torch.int8,
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torch.uint8,
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torch.int16,
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torch.int32,
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)
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assert self.dtype in _ALLOWED_DTYPES, f"Default Observer only works for {_ALLOWED_DTYPES} data type"
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self.has_customized_qrange = (quant_min is not None) and (quant_max is not None)
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if self.has_customized_qrange:
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validate_qmin_qmax(quant_min, quant_max)
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self.quant_min, self.quant_max = \
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calculate_qmin_qmax(quant_min, quant_max, self.has_customized_qrange, self.dtype, self.reduce_range)
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def _load_from_state_dict(
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self,
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state_dict,
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prefix,
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local_metadata,
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strict,
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missing_keys,
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unexpected_keys,
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error_msgs,
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):
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version = local_metadata.get("version", None)
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if version is None or version == 1:
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# eps was moved to a buffer in version 2
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eps = torch.tensor([torch.finfo(torch.float32).eps])
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state_dict[prefix + "eps"] = eps
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super()._load_from_state_dict(
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state_dict,
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prefix,
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local_metadata,
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strict,
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missing_keys,
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unexpected_keys,
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error_msgs,
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)
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@torch.jit.export
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def _validate_qmin_qmax(self, quant_min: int, quant_max: int) -> None:
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r"""Validates that the user-specified quantization range is properly initialized
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and within the given bound supported by the observer dtype.
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To accommodate lower-bit quantization with respect to the existing torch.qint8 and
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torch.quint8 datatypes, the user can choose to use dynamic quantization range by passing
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in a tuple of initial qmin and qmax values. One use case is these customized qmin and qmax
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values are used to calculate static estimates of the scale and zero point for aggressive lower-bit
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fake quantization. These estimates are compared against parameters learned through backpropagation.
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The related literatures for scale and zero point via backpropagation are as follows:
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|
Learned Step Size Quantization: https://openreview.net/pdf?id=rkgO66VKDS
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Trained Quantization Thresholds: https://arxiv.org/pdf/1903.08066.pdf
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"""
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# The variable names are prefixed with "initial" because their values (qmin and qmax) might be adjusted
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# based on whether quantization range is reduced and the datatype (signed/unsigned) used by the observer.
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assert (
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quant_min <= 0 <= quant_max
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), "Used-specified quantization range must include 0."
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assert (
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quant_min < quant_max
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), "qmin must be strictly less than qmax for user-specified quantization range."
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|
@torch.jit.export
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|
def _calculate_qparams(
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self, min_val: torch.Tensor, max_val: torch.Tensor
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|
) -> Tuple[torch.Tensor, torch.Tensor]:
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r"""Calculates the quantization parameters, given min and max
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value tensors. Works for both per tensor and per channel cases
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|
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|
Args:
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min_val: Minimum values per channel
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|
max_val: Maximum values per channel
|
|
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|
Returns:
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|
scales: Scales tensor of shape (#channels,)
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|
zero_points: Zero points tensor of shape (#channels,)
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|
"""
|
|
# Functionally equivalent to 'determine_qparams' in utils.py. Observers must be torchscriptable however and qscheme
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# as far as I can tell is not allowed to passed as a parameter in torchscript functions. This makes refactoring observer
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|
# to use this utility a massive pain and very gross. For now Im opting just to duplicate as this code
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# seems unlikey to change (last update over 1 year ago) and when torchscript is fully deprecated we can refactor.
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# TODO(jakeszwe, jerryzh168)
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if not check_min_max_valid(min_val, max_val):
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return torch.tensor([1.0], device=min_val.device.type), torch.tensor([0], device=min_val.device.type)
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|
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quant_min, quant_max = self.quant_min, self.quant_max
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min_val_neg = torch.min(min_val, torch.zeros_like(min_val))
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max_val_pos = torch.max(max_val, torch.zeros_like(max_val))
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|
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device = min_val_neg.device
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scale = torch.ones(min_val_neg.size(), dtype=torch.float32, device=device)
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zero_point = torch.zeros(min_val_neg.size(), dtype=torch.int64, device=device)
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|
|
|
if (
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self.qscheme == torch.per_tensor_symmetric
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|
or self.qscheme == torch.per_channel_symmetric
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|
):
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|
max_val_pos = torch.max(-min_val_neg, max_val_pos)
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scale = max_val_pos / (float(quant_max - quant_min) / 2)
|
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scale = torch.max(scale, self.eps)
|
|
if self.dtype in [torch.quint8, torch.uint8]:
|
|
if self.has_customized_qrange:
|
|
# When customized quantization range is used, down-rounded midpoint of the range is chosen.
|
|
zero_point = zero_point.new_full(
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|
zero_point.size(), (quant_min + quant_max) // 2
|
|
)
|
|
else:
|
|
zero_point = zero_point.new_full(zero_point.size(), 128)
|
|
elif self.qscheme == torch.per_channel_affine_float_qparams:
|
|
scale = (max_val - min_val) / float(quant_max - quant_min)
|
|
scale = torch.where(scale > self.eps, scale, torch.ones_like(scale))
|
|
# We use the quantize function
|
|
# xq = Round(Xf * inv_scale + zero_point),
|
|
# setting zero_point to (-1 * min *inv_scale) we get
|
|
# Xq = Round((Xf - min) * inv_scale)
|
|
zero_point = -1 * min_val / scale
|
|
else:
|
|
scale = (max_val_pos - min_val_neg) / float(quant_max - quant_min)
|
|
scale = torch.max(scale, self.eps)
|
|
zero_point = quant_min - torch.round(min_val_neg / scale).to(torch.int)
|
|
zero_point = torch.clamp(zero_point, quant_min, quant_max)
|
|
|
|
# For scalar values, cast them to Tensors of size 1 to keep the shape
|
|
# consistent with default values in FakeQuantize.
|
|
if len(scale.shape) == 0:
|
|
# TODO: switch to scale.item() after adding JIT support
|
|
scale = torch.tensor([float(scale)], dtype=scale.dtype, device=device)
|
|
if len(zero_point.shape) == 0:
|
|
# TODO: switch to zero_point.item() after adding JIT support
|
|
zero_point = torch.tensor(
|
|
[int(zero_point)], dtype=zero_point.dtype, device=device
|
|
)
|
|
if self.qscheme == torch.per_channel_affine_float_qparams:
|
|
zero_point = torch.tensor(
|
|
[float(zero_point)], dtype=zero_point.dtype, device=device
|
|
)
|
|
|
|
return scale, zero_point
|
|
|
|
@torch.jit.export
|
|
def reset_min_max_vals(self):
|
|
raise NotImplementedError("Cannot reset min/max values in the given observer.")
|
|
|
|
|
|
# Originally, this class was called `_ObserverBase`. Keeping the old name around
|
|
# for backwards compatibility.
|
|
# TODO(after v1.13): delete this
|
|
_ObserverBase = UniformQuantizationObserverBase
|
|
|
|
|
|
class MinMaxObserver(UniformQuantizationObserverBase):
|
|
r"""Observer module for computing the quantization parameters based on the
|
|
running min and max values.
|
|
|
|
This observer uses the tensor min/max statistics to compute the quantization
|
|
parameters. The module records the running minimum and maximum of incoming
|
|
tensors, and uses this statistic to compute the quantization parameters.
|
|
|
|
Args:
|
|
dtype: dtype argument to the `quantize` node needed to implement the
|
|
reference model spec.
|
|
qscheme: Quantization scheme to be used
|
|
reduce_range: Reduces the range of the quantized data type by 1 bit
|
|
quant_min: Minimum quantization value. If unspecified, it will follow the 8-bit setup.
|
|
quant_max: Maximum quantization value. If unspecified, it will follow the 8-bit setup.
|
|
eps: Epsilon value for float32, Defaults to `torch.finfo(torch.float32).eps`.
|
|
|
|
Given running min/max as :math:`x_\text{min}` and :math:`x_\text{max}`,
|
|
scale :math:`s` and zero point :math:`z` are computed as:
|
|
|
|
The running minimum/maximum :math:`x_\text{min/max}` is computed as:
|
|
|
|
.. math::
|
|
|
|
\begin{array}{ll}
|
|
x_\text{min} &= \begin{cases}
|
|
\min(X) & \text{if~}x_\text{min} = \text{None} \\
|
|
\min\left(x_\text{min}, \min(X)\right) & \text{otherwise}
|
|
\end{cases}\\
|
|
x_\text{max} &= \begin{cases}
|
|
\max(X) & \text{if~}x_\text{max} = \text{None} \\
|
|
\max\left(x_\text{max}, \max(X)\right) & \text{otherwise}
|
|
\end{cases}\\
|
|
\end{array}
|
|
|
|
where :math:`X` is the observed tensor.
|
|
|
|
The scale :math:`s` and zero point :math:`z` are then computed as:
|
|
|
|
.. math::
|
|
|
|
\begin{aligned}
|
|
\text{if Symmetric:}&\\
|
|
&s = 2 \max(|x_\text{min}|, x_\text{max}) /
|
|
\left( Q_\text{max} - Q_\text{min} \right) \\
|
|
&z = \begin{cases}
|
|
0 & \text{if dtype is qint8} \\
|
|
128 & \text{otherwise}
|
|
\end{cases}\\
|
|
\text{Otherwise:}&\\
|
|
&s = \left( x_\text{max} - x_\text{min} \right ) /
|
|
\left( Q_\text{max} - Q_\text{min} \right ) \\
|
|
&z = Q_\text{min} - \text{round}(x_\text{min} / s)
|
|
\end{aligned}
|
|
|
|
where :math:`Q_\text{min}` and :math:`Q_\text{max}` are the minimum and
|
|
maximum of the quantized data type.
|
|
|
|
.. warning:: :attr:`dtype` can only take ``torch.qint8`` or ``torch.quint8``.
|
|
|
|
.. note:: If the running minimum equals to the running maximum, the scale
|
|
and zero_point are set to 1.0 and 0.
|
|
"""
|
|
min_val: torch.Tensor
|
|
max_val: torch.Tensor
|
|
|
|
def __init__(
|
|
self,
|
|
dtype=torch.quint8,
|
|
qscheme=torch.per_tensor_affine,
|
|
reduce_range=False,
|
|
quant_min=None,
|
|
quant_max=None,
|
|
factory_kwargs=None,
|
|
eps=torch.finfo(torch.float32).eps,
|
|
is_dynamic=False,
|
|
**kwargs,
|
|
) -> None:
|
|
if not is_per_tensor(qscheme):
|
|
raise NotImplementedError(
|
|
"MinMaxObserver's qscheme only support torch.per_tensor_symmetric \
|
|
and torch.per_tensor_affine."
|
|
)
|
|
# TODO: MinMaxObserver by itself doesn't support dynamic quantization, but
|
|
# if it's inherited by MovingAverageObserver, and averaging_constant is 1, it
|
|
# supports dynamic quantization, we may need to better error checking here
|
|
|
|
# For x86 quantized kernels, we need to ensure that the vpmaddubsw
|
|
# instruction does not overflow. We allow for a reduce_range argument to
|
|
# observers that reduces the quantized range to (0,127) or (-64, 63).
|
|
# For more details see aten/src/ATen/native/quantized/cpu/qconv.cpp
|
|
# This is not an optimal choice for non x86 backends as it loses a bit
|
|
# of precision for activations.
|
|
super().__init__(
|
|
dtype=dtype,
|
|
qscheme=qscheme,
|
|
reduce_range=reduce_range,
|
|
quant_min=quant_min,
|
|
quant_max=quant_max,
|
|
factory_kwargs=factory_kwargs,
|
|
eps=eps,
|
|
is_dynamic=is_dynamic,
|
|
**kwargs,
|
|
)
|
|
factory_kwargs = torch.nn.factory_kwargs(factory_kwargs)
|
|
self.register_buffer("min_val", torch.tensor(float("inf"), **factory_kwargs))
|
|
self.register_buffer("max_val", torch.tensor(float("-inf"), **factory_kwargs))
|
|
if (
|
|
self.qscheme == torch.per_tensor_symmetric
|
|
and self.reduce_range
|
|
and self.dtype == torch.quint8
|
|
):
|
|
raise NotImplementedError(
|
|
"Cannot reduce range for symmetric \
|
|
quantization for quint8"
|
|
)
|
|
|
|
def forward(self, x_orig):
|
|
r"""Records the running minimum and maximum of ``x``."""
|
|
if x_orig.numel() == 0:
|
|
return x_orig
|
|
x = x_orig.detach() # avoid keeping autograd tape
|
|
x = x.to(self.min_val.dtype)
|
|
min_val_cur, max_val_cur = torch.aminmax(x)
|
|
min_val = torch.min(min_val_cur, self.min_val)
|
|
max_val = torch.max(max_val_cur, self.max_val)
|
|
self.min_val.copy_(min_val)
|
|
self.max_val.copy_(max_val)
|
|
return x_orig
|
|
|
|
@torch.jit.export
|
|
def calculate_qparams(self):
|
|
r"""Calculates the quantization parameters."""
|
|
return self._calculate_qparams(self.min_val, self.max_val)
|
|
|
|
@torch.jit.export
|
|
def extra_repr(self):
|
|
return f"min_val={self.min_val}, max_val={self.max_val}"
|
|
|
|
@torch.jit.export
|
|
def reset_min_max_vals(self):
|
|
"""Resets the min/max values."""
|
|
self.min_val.copy_(torch.tensor(float("inf")))
|
|
self.max_val.copy_(torch.tensor(float("-inf")))
|
|
|
|
class MovingAverageMinMaxObserver(MinMaxObserver):
|
|
r"""Observer module for computing the quantization parameters based on the
|
|
moving average of the min and max values.
|
|
|
|
This observer computes the quantization parameters based on the moving
|
|
averages of minimums and maximums of the incoming tensors. The module
|
|
records the average minimum and maximum of incoming tensors, and uses this
|
|
statistic to compute the quantization parameters.
|
|
|
|
Args:
|
|
averaging_constant: Averaging constant for min/max.
|
|
dtype: dtype argument to the `quantize` node needed to implement the
|
|
reference model spec.
|
|
qscheme: Quantization scheme to be used
|
|
reduce_range: Reduces the range of the quantized data type by 1 bit
|
|
quant_min: Minimum quantization value. If unspecified, it will follow the 8-bit setup.
|
|
quant_max: Maximum quantization value. If unspecified, it will follow the 8-bit setup.
|
|
eps: Epsilon value for float32, Defaults to `torch.finfo(torch.float32).eps`.
|
|
|
|
The moving average min/max is computed as follows
|
|
|
|
.. math::
|
|
|
|
\begin{array}{ll}
|
|
x_\text{min} = \begin{cases}
|
|
\min(X) & \text{if~}x_\text{min} = \text{None} \\
|
|
(1 - c) x_\text{min} + c \min(X) & \text{otherwise}
|
|
\end{cases}\\
|
|
x_\text{max} = \begin{cases}
|
|
\max(X) & \text{if~}x_\text{max} = \text{None} \\
|
|
(1 - c) x_\text{max} + c \max(X) & \text{otherwise}
|
|
\end{cases}\\
|
|
\end{array}
|
|
|
|
where :math:`x_\text{min/max}` is the running average min/max, :math:`X` is
|
|
is the incoming tensor, and :math:`c` is the ``averaging_constant``.
|
|
|
|
The scale and zero point are then computed as in
|
|
:class:`~torch.ao.quantization.observer.MinMaxObserver`.
|
|
|
|
.. note:: Only works with ``torch.per_tensor_affine`` quantization scheme.
|
|
|
|
.. note:: If the running minimum equals to the running maximum, the scale
|
|
and zero_point are set to 1.0 and 0.
|
|
"""
|
|
|
|
def __init__(
|
|
self,
|
|
averaging_constant=0.01,
|
|
dtype=torch.quint8,
|
|
qscheme=torch.per_tensor_affine,
|
|
reduce_range=False,
|
|
quant_min=None,
|
|
quant_max=None,
|
|
eps=torch.finfo(torch.float32).eps,
|
|
is_dynamic=False,
|
|
**kwargs
|
|
) -> None:
|
|
if not is_per_tensor(qscheme):
|
|
raise NotImplementedError(
|
|
f"MovingAverageMinMaxObserver's qscheme only support \
|
|
torch.per_tensor_symmetric and torch.per_tensor_affine. \
|
|
but got: {qscheme}"
|
|
)
|
|
self.averaging_constant = averaging_constant
|
|
if is_dynamic and self.averaging_constant != 1:
|
|
raise NotImplementedError(
|
|
"MovingAverageMinMaxObserver doesn't support dynamic quantization for "
|
|
f"averaging constant of {self.averaging_constant}"
|
|
)
|
|
super().__init__(
|
|
dtype=dtype,
|
|
qscheme=qscheme,
|
|
reduce_range=reduce_range,
|
|
quant_min=quant_min,
|
|
quant_max=quant_max,
|
|
eps=eps,
|
|
is_dynamic=is_dynamic,
|
|
**kwargs
|
|
)
|
|
|
|
def forward(self, x_orig):
|
|
if x_orig.numel() == 0:
|
|
return x_orig
|
|
x = x_orig.detach() # avoid keeping autograd tape
|
|
x = x.to(self.min_val.dtype)
|
|
min_val = self.min_val
|
|
max_val = self.max_val
|
|
if min_val == float("inf") and max_val == float("-inf"):
|
|
min_val, max_val = torch.aminmax(x)
|
|
else:
|
|
min_val_cur, max_val_cur = torch.aminmax(x)
|
|
min_val = min_val + self.averaging_constant * (min_val_cur - min_val)
|
|
max_val = max_val + self.averaging_constant * (max_val_cur - max_val)
|
|
self.min_val.copy_(min_val)
|
|
self.max_val.copy_(max_val)
|
|
return x_orig
|
|
|
|
|
|
class PerChannelMinMaxObserver(UniformQuantizationObserverBase):
|
|
r"""Observer module for computing the quantization parameters based on the
|
|
running per channel min and max values.
|
|
|
|
This observer uses the tensor min/max statistics to compute the per channel
|
|
quantization parameters. The module records the running minimum and maximum
|
|
of incoming tensors, and uses this statistic to compute the quantization
|
|
parameters.
|
|
|
|
Args:
|
|
ch_axis: Channel axis
|
|
dtype: dtype argument to the `quantize` node needed to implement the
|
|
reference model spec.
|
|
qscheme: Quantization scheme to be used
|
|
reduce_range: Reduces the range of the quantized data type by 1 bit
|
|
quant_min: Minimum quantization value. If unspecified, it will follow the 8-bit setup.
|
|
quant_max: Maximum quantization value. If unspecified, it will follow the 8-bit setup.
|
|
eps: Epsilon value for float32, Defaults to `torch.finfo(torch.float32).eps`.
|
|
|
|
The quantization parameters are computed the same way as in
|
|
:class:`~torch.ao.quantization.observer.MinMaxObserver`, with the difference
|
|
that the running min/max values are stored per channel.
|
|
Scales and zero points are thus computed per channel as well.
|
|
|
|
.. note:: If the running minimum equals to the running maximum, the scales
|
|
and zero_points are set to 1.0 and 0.
|
|
"""
|
|
min_val: torch.Tensor
|
|
max_val: torch.Tensor
|
|
|
|
def __init__(
|
|
self,
|
|
ch_axis=0,
|
|
dtype=torch.quint8,
|
|
qscheme=torch.per_channel_affine,
|
|
reduce_range=False,
|
|
quant_min=None,
|
|
quant_max=None,
|
|
factory_kwargs=None,
|
|
eps=torch.finfo(torch.float32).eps,
|
|
is_dynamic=False,
|
|
**kwargs,
|
|
) -> None:
|
|
if not is_per_channel(qscheme):
|
|
raise NotImplementedError(
|
|
"PerChannelMinMaxObserver's qscheme only support \
|
|
torch.per_channel_symmetric, torch.per_channel_affine and torch.per_channel_affine_float_qparams."
|
|
)
|
|
if is_dynamic:
|
|
raise NotImplementedError(
|
|
"PerChannelMinMaxObserver doesn't support dynamic quantization"
|
|
)
|
|
super().__init__(
|
|
dtype=dtype,
|
|
qscheme=qscheme,
|
|
reduce_range=reduce_range,
|
|
quant_min=quant_min,
|
|
quant_max=quant_max,
|
|
factory_kwargs=factory_kwargs,
|
|
eps=eps,
|
|
is_dynamic=is_dynamic,
|
|
**kwargs,
|
|
)
|
|
factory_kwargs = torch.nn.factory_kwargs(factory_kwargs)
|
|
self.ch_axis = ch_axis
|
|
self.register_buffer("min_val", torch.tensor([], **factory_kwargs))
|
|
self.register_buffer("max_val", torch.tensor([], **factory_kwargs))
|
|
if (
|
|
self.qscheme == torch.per_channel_symmetric
|
|
and self.reduce_range
|
|
and self.dtype == torch.quint8
|
|
):
|
|
raise NotImplementedError(
|
|
"Cannot reduce range for symmetric quantization for quint8"
|
|
)
|
|
|
|
def forward(self, x_orig):
|
|
return self._forward(x_orig)
|
|
|
|
def _forward(self, x_orig):
|
|
if x_orig.numel() == 0:
|
|
return x_orig
|
|
x = x_orig.detach() # avoid keeping autograd tape
|
|
min_val = self.min_val
|
|
max_val = self.max_val
|
|
x_dim = x.size()
|
|
|
|
new_axis_list = [i for i in range(len(x_dim))] # noqa: C416
|
|
new_axis_list[self.ch_axis] = 0
|
|
new_axis_list[0] = self.ch_axis
|
|
y = x.permute(new_axis_list)
|
|
# Need to match dtype of min/max because the updates to buffers
|
|
# are done in place and types need to match for comparisons
|
|
y = y.to(self.min_val.dtype)
|
|
y = torch.flatten(y, start_dim=1)
|
|
if min_val.numel() == 0 or max_val.numel() == 0:
|
|
min_val, max_val = torch.aminmax(y, dim=1)
|
|
else:
|
|
min_val_cur, max_val_cur = torch.aminmax(y, dim=1)
|
|
min_val = torch.min(min_val_cur, min_val)
|
|
max_val = torch.max(max_val_cur, max_val)
|
|
self.min_val.resize_(min_val.shape)
|
|
self.max_val.resize_(max_val.shape)
|
|
self.min_val.copy_(min_val)
|
|
self.max_val.copy_(max_val)
|
|
return x_orig
|
|
|
|
@torch.jit.export
|
|
def calculate_qparams(self):
|
|
return self._calculate_qparams(self.min_val, self.max_val)
|
|
|
|
def extra_repr(self):
|
|
return f"min_val={self.min_val}, max_val={self.max_val}"
|
|
|
|
def _load_from_state_dict(
|
|
self,
|
|
state_dict: Dict[str, Any],
|
|
prefix: str,
|
|
local_metadata: Dict[str, torch.Tensor],
|
|
strict: bool,
|
|
missing_keys: List[str],
|
|
unexpected_keys: List[str],
|
|
error_msgs: List[str],
|
|
):
|
|
version = local_metadata.get("version", None)
|
|
if version is not None and version < 3:
|
|
local_state = ["min_vals", "max_vals"]
|
|
expected_min_name = "min_vals"
|
|
expected_max_name = "max_vals"
|
|
else:
|
|
local_state = ["min_val", "max_val"]
|
|
expected_min_name = "min_val"
|
|
expected_max_name = "max_val"
|
|
for name in local_state:
|
|
key = prefix + name
|
|
if key in state_dict:
|
|
val = state_dict[key]
|
|
# Custom handling to allow loading min_val or max_val
|
|
# of size N into uninitialized buffers of size 0. The
|
|
# buffers are resized here, and the values are copied in
|
|
# the default state_dict loading code of the parent.
|
|
if name == expected_min_name:
|
|
self.min_val.resize_(val.shape)
|
|
elif name == expected_max_name:
|
|
self.max_val.resize_(val.shape)
|
|
else:
|
|
warnings.warn(f"Observer load_from_state_dict got unexpected name {name}")
|
|
# For torchscript module we need to update the attributes here since we do not
|
|
# call the `_load_from_state_dict` function defined module.py
|
|
if torch.jit.is_scripting():
|
|
if name == expected_min_name:
|
|
self.min_val.copy_(val)
|
|
elif name == expected_max_name:
|
|
self.max_val.copy_(val)
|
|
else:
|
|
warnings.warn(f"Observer load_from_state_dict got unexpected name {name}")
|
|
elif strict:
|
|
missing_keys.append(key)
|
|
|
|
if not torch.jit.is_scripting():
|
|
super()._load_from_state_dict(
|
|
state_dict,
|
|
prefix,
|
|
local_metadata,
|
|
False,
|
|
missing_keys,
|
|
unexpected_keys,
|
|
error_msgs,
|
|
)
|
|
|
|
def _load_from_state_dict_script(
|
|
self,
|
|
state_dict: Dict[str, Any],
|
|
prefix: str,
|
|
local_metadata: Dict[str, torch.Tensor],
|
|
strict: bool,
|
|
missing_keys: List[str],
|
|
unexpected_keys: List[str],
|
|
error_msgs: List[str],
|
|
):
|
|
|
|
self._load_from_state_dict(
|
|
state_dict,
|
|
prefix,
|
|
local_metadata,
|
|
strict,
|
|
missing_keys,
|
|
unexpected_keys,
|
|
error_msgs,
|
|
)
|
|
|
|
@torch.jit.export
|
|
def reset_min_max_vals(self):
|
|
"""Resets the min/max values."""
|
|
# This used to be torch.ones but that does not work because
|
|
# JIT compiler can optimize it via common subexpression elimination
|
|
# in which case both min_val and max_val point to the same tensor.
|
|
self.min_val = torch.rand(0, )
|
|
self.max_val = torch.rand(0, )
|
|
|
|
|
|
class MovingAveragePerChannelMinMaxObserver(PerChannelMinMaxObserver):
|
|
r"""Observer module for computing the quantization parameters based on the
|
|
running per channel min and max values.
|
|
|
|
This observer uses the tensor min/max statistics to compute the per channel
|
|
quantization parameters. The module records the running minimum and maximum
|
|
of incoming tensors, and uses this statistic to compute the quantization
|
|
parameters.
|
|
|
|
Args:
|
|
averaging_constant: Averaging constant for min/max.
|
|
ch_axis: Channel axis
|
|
dtype: Quantized data type
|
|
qscheme: Quantization scheme to be used
|
|
reduce_range: Reduces the range of the quantized data type by 1 bit
|
|
quant_min: Minimum quantization value. If unspecified, it will follow the 8-bit setup.
|
|
quant_max: Maximum quantization value. If unspecified, it will follow the 8-bit setup.
|
|
eps: Epsilon value for float32, Defaults to `torch.finfo(torch.float32).eps`.
|
|
|
|
The quantization parameters are computed the same way as in
|
|
:class:`~torch.ao.quantization.observer.MovingAverageMinMaxObserver`, with the
|
|
difference that the running min/max values are stored per channel.
|
|
Scales and zero points are thus computed per channel as well.
|
|
|
|
.. note:: If the running minimum equals to the running maximum, the scales
|
|
and zero_points are set to 1.0 and 0.
|
|
"""
|
|
|
|
def __init__(
|
|
self,
|
|
averaging_constant=0.01,
|
|
ch_axis=0,
|
|
dtype=torch.quint8,
|
|
qscheme=torch.per_channel_affine,
|
|
reduce_range=False,
|
|
quant_min=None,
|
|
quant_max=None,
|
|
eps=torch.finfo(torch.float32).eps,
|
|
is_dynamic=False,
|
|
**kwargs
|
|
) -> None:
|
|
if not is_per_channel(qscheme):
|
|
raise NotImplementedError(
|
|
"MovingAveragePerChannelMinMaxObserver's qscheme only support \
|
|
torch.per_channel_symmetric, torch.per_channel_affine and torch.per_channel_affine_float_qparams."
|
|
)
|
|
if is_dynamic:
|
|
raise NotImplementedError(
|
|
"MovingAveragePerChannelMinMaxObserver doesn't support dynamic quantization"
|
|
)
|
|
super().__init__(
|
|
ch_axis=ch_axis,
|
|
dtype=dtype,
|
|
qscheme=qscheme,
|
|
reduce_range=reduce_range,
|
|
quant_min=quant_min,
|
|
quant_max=quant_max,
|
|
eps=eps,
|
|
is_dynamic=is_dynamic,
|
|
**kwargs
|
|
)
|
|
self.averaging_constant = averaging_constant
|
|
|
|
def forward(self, x_orig):
|
|
if x_orig.numel() == 0:
|
|
return x_orig
|
|
x = x_orig.detach() # avoid keeping autograd tape
|
|
x = x.to(self.min_val.dtype)
|
|
min_val = self.min_val
|
|
max_val = self.max_val
|
|
x_dim = x.size()
|
|
|
|
new_axis_list = [i for i in range(len(x_dim))] # noqa: C416
|
|
new_axis_list[self.ch_axis] = 0
|
|
new_axis_list[0] = self.ch_axis
|
|
y = x.permute(new_axis_list)
|
|
y = torch.flatten(y, start_dim=1)
|
|
if min_val.numel() == 0 or max_val.numel() == 0:
|
|
min_val, max_val = torch.aminmax(y, dim=1)
|
|
else:
|
|
min_val_cur, max_val_cur = torch.aminmax(y, dim=1)
|
|
min_val = min_val + self.averaging_constant * (min_val_cur - min_val)
|
|
max_val = max_val + self.averaging_constant * (max_val_cur - max_val)
|
|
self.min_val.resize_(min_val.shape)
|
|
self.max_val.resize_(max_val.shape)
|
|
self.min_val.copy_(min_val)
|
|
self.max_val.copy_(max_val)
|
|
return x_orig
|
|
|
|
|
|
class HistogramObserver(UniformQuantizationObserverBase):
|
|
r"""
|
|
The module records the running histogram of tensor values along with
|
|
min/max values. ``calculate_qparams`` will calculate scale and zero_point.
|
|
|
|
Args:
|
|
bins: Number of bins to use for the histogram
|
|
upsample_rate: Factor by which the histograms are upsampled, this is
|
|
used to interpolate histograms with varying ranges across observations
|
|
dtype: dtype argument to the `quantize` node needed to implement the
|
|
reference model spec
|
|
qscheme: Quantization scheme to be used
|
|
reduce_range: Reduces the range of the quantized data type by 1 bit
|
|
eps: Epsilon value for float32, Defaults to `torch.finfo(torch.float32).eps`.
|
|
|
|
The scale and zero point are computed as follows:
|
|
|
|
1. Create the histogram of the incoming inputs.
|
|
The histogram is computed continuously, and the ranges per bin change
|
|
with every new tensor observed.
|
|
2. Search the distribution in the histogram for optimal min/max values.
|
|
The search for the min/max values ensures the minimization of the
|
|
quantization error with respect to the floating point model.
|
|
3. Compute the scale and zero point the same way as in the
|
|
:class:`~torch.ao.quantization.MinMaxObserver`
|
|
"""
|
|
histogram: torch.Tensor
|
|
min_val: torch.Tensor
|
|
max_val: torch.Tensor
|
|
|
|
def __init__(
|
|
self,
|
|
bins: int = 2048,
|
|
upsample_rate: int = 128,
|
|
dtype: torch.dtype = torch.quint8,
|
|
qscheme=torch.per_tensor_affine,
|
|
reduce_range=False,
|
|
quant_min=None,
|
|
quant_max=None,
|
|
factory_kwargs=None,
|
|
eps=torch.finfo(torch.float32).eps,
|
|
is_dynamic=False,
|
|
**kwargs,
|
|
) -> None:
|
|
if not is_per_tensor(qscheme):
|
|
raise NotImplementedError(
|
|
"HistogramObserver's qscheme only support torch.per_tensor_symmetric \
|
|
and torch.per_tensor_affine."
|
|
)
|
|
if is_dynamic:
|
|
raise NotImplementedError(
|
|
"HistogramObserver doesn't support dynamic quantization"
|
|
)
|
|
# bins: The number of bins used for histogram calculation.
|
|
super().__init__(
|
|
dtype=dtype,
|
|
qscheme=qscheme,
|
|
reduce_range=reduce_range,
|
|
quant_min=quant_min,
|
|
quant_max=quant_max,
|
|
factory_kwargs=factory_kwargs,
|
|
eps=eps,
|
|
is_dynamic=is_dynamic,
|
|
**kwargs
|
|
)
|
|
factory_kwargs = torch.nn.factory_kwargs(factory_kwargs)
|
|
self.bins = bins
|
|
self.register_buffer("histogram", torch.zeros(self.bins, **factory_kwargs))
|
|
self.register_buffer("min_val", torch.tensor(float("inf"), **factory_kwargs))
|
|
self.register_buffer("max_val", torch.tensor(float("-inf"), **factory_kwargs))
|
|
self.dst_nbins = 2 ** torch.iinfo(self.dtype).bits
|
|
self.upsample_rate = upsample_rate
|
|
|
|
def _get_norm(
|
|
self, delta_begin: torch.Tensor, delta_end: torch.Tensor, density: torch.Tensor
|
|
) -> torch.Tensor:
|
|
r"""
|
|
Compute the norm of the values uniformaly distributed between
|
|
delta_begin and delta_end.
|
|
Currently only L2 norm is supported.
|
|
|
|
norm = density * (integral_{begin, end} x^2)
|
|
= density * (end^3 - begin^3) / 3
|
|
"""
|
|
norm = (
|
|
delta_end * delta_end * delta_end - delta_begin * delta_begin * delta_begin
|
|
) / 3
|
|
return density * norm
|
|
|
|
def _compute_quantization_error(self, next_start_bin: int, next_end_bin: int):
|
|
r"""
|
|
Compute the quantization error if we use start_bin to end_bin as the
|
|
min and max to do the quantization.
|
|
"""
|
|
bin_width = (self.max_val.item() - self.min_val.item()) / self.bins
|
|
|
|
dst_bin_width = bin_width * (next_end_bin - next_start_bin + 1) / self.dst_nbins
|
|
if dst_bin_width == 0.0:
|
|
return 0.0
|
|
|
|
src_bin = torch.arange(self.bins, device=self.histogram.device)
|
|
# distances from the beginning of first dst_bin to the beginning and
|
|
# end of src_bin
|
|
src_bin_begin = (src_bin - next_start_bin) * bin_width
|
|
src_bin_end = src_bin_begin + bin_width
|
|
|
|
# which dst_bins the beginning and end of src_bin belong to?
|
|
dst_bin_of_begin = torch.clamp(
|
|
torch.div(src_bin_begin, dst_bin_width, rounding_mode='floor'), 0, self.dst_nbins - 1
|
|
)
|
|
dst_bin_of_begin_center = (dst_bin_of_begin + 0.5) * dst_bin_width
|
|
|
|
dst_bin_of_end = torch.clamp(
|
|
torch.div(src_bin_end, dst_bin_width, rounding_mode='floor'), 0, self.dst_nbins - 1
|
|
)
|
|
density = self.histogram / bin_width
|
|
|
|
norm = torch.zeros(self.bins, device=self.histogram.device)
|
|
|
|
delta_begin = src_bin_begin - dst_bin_of_begin_center
|
|
delta_end = dst_bin_width / 2
|
|
norm += self._get_norm(delta_begin,
|
|
torch.ones(self.bins, device=self.histogram.device) * delta_end,
|
|
density)
|
|
|
|
norm += (dst_bin_of_end - dst_bin_of_begin - 1) * self._get_norm(
|
|
torch.tensor(-dst_bin_width / 2), torch.tensor(dst_bin_width / 2), density
|
|
)
|
|
|
|
dst_bin_of_end_center = dst_bin_of_end * dst_bin_width + dst_bin_width / 2
|
|
|
|
delta_begin = -dst_bin_width / 2
|
|
delta_end = src_bin_end - dst_bin_of_end_center
|
|
norm += self._get_norm(torch.tensor(delta_begin), delta_end, density)
|
|
|
|
return norm.sum().item()
|
|
|
|
def _non_linear_param_search(self) -> Tuple[torch.Tensor, torch.Tensor]:
|
|
r"""Non-linear parameter search.
|
|
|
|
An approximation for L2 error minimization for selecting min/max.
|
|
By selecting new min/max, we filter out outliers in input distribution.
|
|
This follows the implementation of NormMinimization::NonlinearQuantizationParamsSearch in
|
|
caffe2/quantization/server/norm_minimization.cc
|
|
"""
|
|
assert self.histogram.size()[0] == self.bins, "bins mismatch"
|
|
bin_width = (self.max_val - self.min_val) / self.bins
|
|
|
|
# cumulative sum
|
|
total = torch.sum(self.histogram).item()
|
|
cSum = torch.cumsum(self.histogram, dim=0)
|
|
|
|
stepsize = 1e-5 # granularity
|
|
alpha = 0.0 # lower bound
|
|
beta = 1.0 # upper bound
|
|
start_bin = 0
|
|
end_bin = self.bins - 1
|
|
norm_min = float("inf")
|
|
|
|
while alpha < beta:
|
|
# Find the next step
|
|
next_alpha = alpha + stepsize
|
|
next_beta = beta - stepsize
|
|
|
|
# find the left and right bins between the quantile bounds
|
|
l = start_bin
|
|
r = end_bin
|
|
while l < end_bin and cSum[l] < next_alpha * total:
|
|
l = l + 1
|
|
while r > start_bin and cSum[r] > next_beta * total:
|
|
r = r - 1
|
|
|
|
# decide the next move
|
|
next_start_bin = start_bin
|
|
next_end_bin = end_bin
|
|
if (l - start_bin) > (end_bin - r):
|
|
# move the start bin
|
|
next_start_bin = l
|
|
alpha = next_alpha
|
|
else:
|
|
# move the end bin
|
|
next_end_bin = r
|
|
beta = next_beta
|
|
|
|
if next_start_bin == start_bin and next_end_bin == end_bin:
|
|
continue
|
|
|
|
# calculate the quantization error using next_start_bin and next_end_bin
|
|
norm = self._compute_quantization_error(next_start_bin, next_end_bin)
|
|
|
|
if norm > norm_min:
|
|
break
|
|
norm_min = norm
|
|
start_bin = next_start_bin
|
|
end_bin = next_end_bin
|
|
|
|
new_min = self.min_val + bin_width * start_bin
|
|
new_max = self.min_val + bin_width * (end_bin + 1)
|
|
return new_min, new_max
|
|
|
|
def _adjust_min_max(
|
|
self, combined_min: torch.Tensor, combined_max: torch.Tensor, upsample_rate: int
|
|
) -> Tuple[torch.Tensor, torch.Tensor, int, int]:
|
|
# We ensure that:
|
|
# (combined_max - combined_min)/(downsample_rate*Nbins) = (max - min)/(upsample_rate*Nbins)
|
|
# This allows us to have a common grid of resolution s, where we can align
|
|
# the input histogram
|
|
# start_idx maps min_val to the histogram bin index.
|
|
|
|
# Compute the width of histogram bins is a straightforward solution, where
|
|
# hist_bin_width = (self.max_val - self.min_val) / (self.bins * upsample_rate)
|
|
# Underflow happens if the numerator is close to the smallest positive subnormal number of FP32
|
|
# Therefore, we avoid such division operation.
|
|
downsample_rate = int(
|
|
torch.ceil(
|
|
((combined_max - combined_min) / (self.max_val - self.min_val)) * upsample_rate
|
|
).item()
|
|
)
|
|
e = downsample_rate / upsample_rate * (self.max_val - self.min_val) - (combined_max - combined_min)
|
|
start_idx = int(
|
|
torch.round((self.min_val - combined_min) / (self.max_val - self.min_val) * self.bins * upsample_rate).item()
|
|
)
|
|
combined_max = combined_max + e
|
|
return combined_min, combined_max, downsample_rate, start_idx
|
|
|
|
def _combine_histograms(
|
|
self,
|
|
orig_hist: torch.Tensor,
|
|
new_hist: torch.Tensor,
|
|
upsample_rate: int,
|
|
downsample_rate: int,
|
|
start_idx: int,
|
|
Nbins: int,
|
|
) -> torch.Tensor:
|
|
# First up-sample the histogram with new data by a factor of L
|
|
# This creates an approximate probability density thats piecewise constant
|
|
upsampled_histogram = new_hist.repeat_interleave(upsample_rate)
|
|
# Now insert the upsampled histogram into the output
|
|
# histogram, which is initialized with zeros.
|
|
# The offset at which the histogram is introduced is determined
|
|
# by the start index as the output histogram can cover a wider range
|
|
histogram_with_output_range = torch.zeros(
|
|
(Nbins * downsample_rate), device=orig_hist.device
|
|
)
|
|
histogram_with_output_range[
|
|
start_idx : Nbins * upsample_rate + start_idx
|
|
] = upsampled_histogram
|
|
# Compute integral histogram, double precision is needed to ensure
|
|
# that there are no overflows
|
|
integral_histogram = torch.cumsum(
|
|
histogram_with_output_range, 0, dtype=torch.double
|
|
)[downsample_rate - 1 :: downsample_rate]
|
|
# Finally perform interpolation
|
|
shifted_integral_histogram = torch.zeros((Nbins), device=orig_hist.device)
|
|
shifted_integral_histogram[1:Nbins] = integral_histogram[0:-1]
|
|
interpolated_histogram = (
|
|
integral_histogram - shifted_integral_histogram
|
|
) / upsample_rate
|
|
orig_hist = orig_hist + interpolated_histogram.to(torch.float)
|
|
return orig_hist
|
|
|
|
def forward(self, x_orig: torch.Tensor) -> torch.Tensor:
|
|
if x_orig.numel() == 0:
|
|
return x_orig
|
|
x = x_orig.detach()
|
|
x_min, x_max = torch.aminmax(x)
|
|
# want to ignore torch.inf since we don't actually
|
|
# want to make our quantization range infinite
|
|
# and in practice those values will be clamped
|
|
if x_min == -torch.inf or x_max == torch.inf:
|
|
warnings.warn("torch.inf detected in input tensor, ignoring input")
|
|
x = x[x.abs() != torch.inf]
|
|
if x.numel() == 0:
|
|
return x_orig
|
|
x_min, x_max = torch.aminmax(x)
|
|
min_val = self.min_val
|
|
max_val = self.max_val
|
|
same_values = min_val.item() == max_val.item()
|
|
is_uninitialized = min_val == float("inf") and max_val == float("-inf")
|
|
if is_uninitialized or same_values:
|
|
min_val, max_val = x_min, x_max
|
|
self.min_val.resize_(min_val.shape)
|
|
self.min_val.copy_(min_val)
|
|
self.max_val.resize_(max_val.shape)
|
|
self.max_val.copy_(max_val)
|
|
assert (
|
|
min_val.numel() == 1 and max_val.numel() == 1
|
|
), "histogram min/max values must be scalar."
|
|
torch.histc(
|
|
x, self.bins, min=min_val, max=max_val, out=self.histogram # type: ignore[arg-type]
|
|
)
|
|
else:
|
|
new_min, new_max = x_min, x_max
|
|
combined_min = torch.min(new_min, min_val)
|
|
combined_max = torch.max(new_max, max_val)
|
|
# combine the existing histogram and new histogram into 1 histogram
|
|
# We do this by first upsampling the histogram to a dense grid
|
|
# and then downsampling the histogram efficiently
|
|
(
|
|
combined_min,
|
|
combined_max,
|
|
downsample_rate,
|
|
start_idx,
|
|
) = self._adjust_min_max(combined_min, combined_max, self.upsample_rate)
|
|
assert (
|
|
combined_min.numel() == 1 and combined_max.numel() == 1
|
|
), "histogram min/max values must be scalar."
|
|
|
|
# TODO: For some reason, this is required for it to pass torchscript test
|
|
# combined_min and combined_max should already have requires_grad set to False
|
|
combined_min, combined_max = combined_min.detach(), combined_max.detach()
|
|
|
|
combined_histogram = torch.histc(
|
|
x, self.bins, min=combined_min, max=combined_max # type: ignore[arg-type]
|
|
)
|
|
if combined_min == min_val and combined_max == max_val:
|
|
combined_histogram += self.histogram
|
|
else:
|
|
combined_histogram = self._combine_histograms(
|
|
combined_histogram,
|
|
self.histogram,
|
|
self.upsample_rate,
|
|
downsample_rate,
|
|
start_idx,
|
|
self.bins,
|
|
)
|
|
|
|
self.histogram.detach_().resize_(combined_histogram.shape)
|
|
self.histogram.copy_(combined_histogram)
|
|
self.min_val.detach_().resize_(combined_min.shape)
|
|
self.min_val.copy_(combined_min)
|
|
self.max_val.detach_().resize_(combined_max.shape)
|
|
self.max_val.copy_(combined_max)
|
|
return x_orig
|
|
|
|
@torch.jit.export
|
|
def calculate_qparams(self):
|
|
is_uninitialized = self.min_val == float("inf") and self.max_val == float(
|
|
"-inf"
|
|
)
|
|
if is_uninitialized:
|
|
warnings.warn(
|
|
"must run observer before calling calculate_qparams.\
|
|
Returning default scale and zero point "
|
|
)
|
|
return torch.tensor([1.0], device=self.min_val.device.type), torch.tensor([0], device=self.min_val.device.type)
|
|
assert self.bins == len(self.histogram), (
|
|
"The number of bins in histogram should be equal to the number of bins "
|
|
"supplied while making this observer"
|
|
)
|
|
|
|
new_min, new_max = self._non_linear_param_search()
|
|
|
|
return self._calculate_qparams(new_min, new_max)
|
|
|
|
def _save_to_state_dict(self, destination, prefix, keep_vars):
|
|
super()._save_to_state_dict(destination, prefix, keep_vars)
|
|
destination[prefix + "min_val"] = self.min_val
|
|
destination[prefix + "max_val"] = self.max_val
|
|
|
|
def _load_from_state_dict(
|
|
self,
|
|
state_dict,
|
|
prefix,
|
|
local_metadata,
|
|
strict,
|
|
missing_keys,
|
|
unexpected_keys,
|
|
error_msgs,
|
|
):
|
|
version = local_metadata.get("version", None)
|
|
|
|
if version is None or version < 3:
|
|
# if min_val and max_val are not initialized, update their shape
|
|
# to account for the differences between v2 and v3
|
|
min_val_name, max_val_name = prefix + "min_val", prefix + "max_val"
|
|
if min_val_name in state_dict:
|
|
if state_dict[min_val_name].shape == torch.Size([0]):
|
|
state_dict[min_val_name] = torch.tensor(float("inf"))
|
|
if max_val_name in state_dict:
|
|
if state_dict[max_val_name].shape == torch.Size([0]):
|
|
state_dict[max_val_name] = torch.tensor(float("-inf"))
|
|
|
|
local_state = ["min_val", "max_val"]
|
|
for name in local_state:
|
|
key = prefix + name
|
|
if key in state_dict:
|
|
val = state_dict[key]
|
|
setattr(self, name, val)
|
|
elif strict:
|
|
missing_keys.append(key)
|
|
super()._load_from_state_dict(
|
|
state_dict,
|
|
prefix,
|
|
local_metadata,
|
|
strict,
|
|
missing_keys,
|
|
unexpected_keys,
|
|
error_msgs,
|
|
)
|
|
|
|
def extra_repr(self):
|
|
return f"min_val={self.min_val}, max_val={self.max_val}"
|
|
|
|
|
|
class FixedQParamsObserver(ObserverBase):
|
|
r"""
|
|
Observer that simulates quantize and dequantize with fixed
|
|
quantization parameters in training time. Only per tensor
|
|
quantization is supported.
|
|
|
|
Args:
|
|
`scale` (float): fixed scale for the observer
|
|
`zero_point` (int): fixed zero point for the observer
|
|
`dtype`, `qscheme`, `quant_min`, `quant_max`
|
|
"""
|
|
|
|
scale: torch.Tensor
|
|
zero_point: torch.Tensor
|
|
|
|
def __init__(
|
|
self,
|
|
scale,
|
|
zero_point,
|
|
dtype=torch.quint8,
|
|
qscheme=torch.per_tensor_affine,
|
|
quant_min=0,
|
|
quant_max=255,
|
|
is_dynamic=False,
|
|
**kwargs,
|
|
):
|
|
if is_dynamic:
|
|
raise NotImplementedError(
|
|
"FixedQParamsObserver doesn't support dynamic quantization"
|
|
)
|
|
super().__init__(dtype=dtype, is_dynamic=is_dynamic, **kwargs)
|
|
self.quant_min = quant_min
|
|
self.quant_max = quant_max
|
|
self.register_buffer('scale', torch.tensor([scale], dtype=torch.float))
|
|
self.register_buffer('zero_point', torch.tensor([zero_point], dtype=torch.int))
|
|
self.dtype = dtype
|
|
self.qscheme = qscheme
|
|
|
|
def forward(self, X):
|
|
return X
|
|
|
|
@torch.jit.export
|
|
def calculate_qparams(self):
|
|
return self.scale, self.zero_point
|
|
|
|
|
|
class PlaceholderObserver(ObserverBase):
|
|
r"""
|
|
Observer that doesn't do anything and just passes its configuration to the
|
|
quantized module's ``.from_float()``.
|
|
|
|
Can be used for quantization to float16 which doesn't require determining
|
|
ranges.
|
|
|
|
Args:
|
|
dtype: dtype argument to the `quantize` node needed to implement the
|
|
reference model spec.
|
|
quant_min: minimum value in quantized domain (TODO: align behavior with other observers)
|
|
quant_max: maximum value in quantized domain
|
|
custom_op_name: (temporary) specify this observer for an operator that doesn't require any observation
|
|
(Can be used in Graph Mode Passes for special case ops).
|
|
compute_dtype (deprecated): if set, marks the future quantize function to use
|
|
dynamic quantization instead of static quantization.
|
|
This field is deprecated, use `is_dynamic=True` instead.
|
|
is_dynamic: if True, the `quantize` function in the reference model
|
|
representation taking stats from this observer instance will
|
|
use dynamic quantization.
|
|
"""
|
|
|
|
def __init__(
|
|
self, dtype=torch.float32, custom_op_name="", compute_dtype=None,
|
|
quant_min=None, quant_max=None, qscheme=None, eps=None,
|
|
is_dynamic=False,
|
|
) -> None:
|
|
super().__init__(dtype=dtype, is_dynamic=is_dynamic)
|
|
if qscheme is None:
|
|
qscheme = torch.per_tensor_affine
|
|
if eps is None:
|
|
eps = torch.finfo(torch.float32).eps
|
|
|
|
# dtype of input of the target operator, e.g. for dynamic quantization
|
|
# ops, the dtype will be float32
|
|
self.dtype = dtype
|
|
self.qscheme = qscheme
|
|
self.quant_min = quant_min
|
|
self.quant_max = quant_max
|
|
self.eps = eps
|
|
self.custom_op = custom_op_name
|
|
# used for configuration of computation type for dynamic quantization
|
|
if compute_dtype:
|
|
is_dynamic = True
|
|
warnings.warn(
|
|
"Please use `is_dynamic` instead of `compute_dtype`. \
|
|
`compute_dtype` will be deprecated in a future release \
|
|
of PyTorch."
|
|
)
|
|
|
|
def forward(self, x):
|
|
return x
|
|
|
|
@torch.jit.export
|
|
def extra_repr(self):
|
|
return f"dtype={self.dtype}, is_dynamic={self.is_dynamic}"
|
|
|
|
@torch.jit.export
|
|
def calculate_qparams(self):
|
|
raise Exception(
|
|
"calculate_qparams should not be called for PlaceholderObserver"
|
|
)
|
|
|
|
|
|
class RecordingObserver(ObserverBase):
|
|
r"""
|
|
The module is mainly for debug and records the tensor values during runtime.
|
|
|
|
Args:
|
|
dtype: Quantized data type
|
|
qscheme: Quantization scheme to be used
|
|
reduce_range: Reduces the range of the quantized data type by 1 bit
|
|
"""
|
|
__annotations__ = {"tensor_val": List[Optional[torch.Tensor]]}
|
|
|
|
def __init__(self, dtype=torch.quint8):
|
|
super().__init__(dtype=dtype, is_dynamic=False) # type: ignore[call-arg]
|
|
self.tensor_val = []
|
|
|
|
def forward(self, x):
|
|
self.tensor_val.append(x.clone())
|
|
return x
|
|
|
|
@torch.jit.export
|
|
def calculate_qparams(self):
|
|
raise Exception("calculate_qparams should not be called for RecordingObserver")
|
|
|
|
@torch.jit.export
|
|
def get_tensor_value(self):
|
|
return self.tensor_val
|
|
|
|
|
|
class NoopObserver(ObserverBase):
|
|
r"""
|
|
Observer that doesn't do anything and just passes its configuration to the
|
|
quantized module's ``.from_float()``.
|
|
|
|
Primarily used for quantization to float16 which doesn't require determining
|
|
ranges.
|
|
|
|
Args:
|
|
dtype: Quantized data type
|
|
custom_op_name: (temporary) specify this observer for an operator that doesn't require any observation
|
|
(Can be used in Graph Mode Passes for special case ops).
|
|
"""
|
|
|
|
def __init__(self, dtype=torch.float16, custom_op_name="") -> None:
|
|
super().__init__(dtype=dtype, is_dynamic=False)
|
|
self.dtype = dtype
|
|
self.custom_op = custom_op_name
|
|
|
|
def forward(self, x):
|
|
return x
|
|
|
|
@torch.jit.export
|
|
def calculate_qparams(self):
|
|
raise Exception("calculate_qparams should not be called for NoopObserver")
|
|
|
|
class ReuseInputObserver(ObserverBase):
|
|
r""" This observer is used when we want to reuse the observer from the operator
|
|
that produces the input Tensor, typically used for operators like reshape, e.g.
|
|
```
|
|
x0 = ...
|
|
x1 = x0.reshape()
|
|
```
|
|
if we configure x0 to be observed by some observer, let's say MinMaxObserver,
|
|
and reshape is configured with ReuseInputObserver, we'll reuse the observer instance
|
|
for x0 for x1 (output of reshape). If x0 is not observed, we also won't observe x1.
|
|
|
|
Note: this is only enabled in FX Graph Mode Quantization
|
|
"""
|
|
def __init__(self):
|
|
super().__init__(torch.quint8, is_dynamic=False)
|
|
|
|
def forward(self, x):
|
|
return x
|
|
|
|
@torch.jit.export
|
|
def calculate_qparams(self):
|
|
raise Exception("calculate_qparams should not be called for ReuseInputObserver")
|
|
|
|
def _is_observer_script_module(mod, obs_type_name):
|
|
"""Returns true if given mod is an instance of Observer script module."""
|
|
if isinstance(mod, torch.jit.RecursiveScriptModule):
|
|
# qualified name looks like '__torch__.torch.ao.quantization.observer.___torch_mangle_2.MinMaxObserver'
|
|
suffix = mod._c.qualified_name.split(".", 1)[1]
|
|
name = re.sub(r"\.___torch_mangle_\d+", "", suffix)
|
|
return obs_type_name in name
|
|
return False
|
|
|
|
|
|
def _is_activation_post_process(module):
|
|
return (
|
|
isinstance(module, (torch.ao.quantization.ObserverBase,
|
|
torch.ao.quantization.FakeQuantizeBase)) or _is_observer_script_module(module, "quantization.observer")
|
|
)
|
|
|
|
|
|
def _is_per_channel_script_obs_instance(module):
|
|
if isinstance(module, torch.jit.RecursiveScriptModule):
|
|
return _is_observer_script_module(
|
|
module, "quantization.observer.PerChannelMinMaxObserver"
|
|
) or _is_observer_script_module(
|
|
module, "quantization.observer.MovingAveragePerChannelMinMaxObserver"
|
|
)
|
|
return False
|
|
|
|
|
|
def get_observer_state_dict(mod):
|
|
r"""
|
|
Returns the state dict corresponding to the observer stats.
|
|
Traverse the model state_dict and extract out the stats.
|
|
"""
|
|
od = OrderedDict()
|
|
if isinstance(mod, torch.jit.RecursiveScriptModule):
|
|
for k, v in mod.state_dict().items():
|
|
if "observer" in k:
|
|
od[k] = v
|
|
else:
|
|
# path for GraphModule and nn.Module (eager mode)
|
|
for k, v in mod.state_dict().items():
|
|
if "activation_post_process" in k:
|
|
od[k] = v
|
|
od._metadata = mod.state_dict()._metadata # type: ignore[attr-defined]
|
|
return od
|
|
|
|
|
|
def load_observer_state_dict(mod, obs_dict):
|
|
r"""
|
|
Given input model and a state_dict containing model observer stats,
|
|
load the stats back into the model. The observer state_dict can be saved
|
|
using torch.ao.quantization.get_observer_state_dict
|
|
"""
|
|
missing_keys: List[str] = []
|
|
unexpected_keys: List[str] = []
|
|
for name, module in mod.named_modules():
|
|
prefix = name + "."
|
|
if _is_activation_post_process(module):
|
|
if _is_per_channel_script_obs_instance(module):
|
|
# For per-channel observers we need to call a custom load_from_state_dict to resize the tensor.
|
|
# However this is not called when the module is scripted and we end up calling the default one in module.py
|
|
module._load_from_state_dict_script(
|
|
obs_dict, prefix, {}, True, missing_keys, unexpected_keys, []
|
|
)
|
|
else:
|
|
module._load_from_state_dict(
|
|
obs_dict, prefix, {}, False, missing_keys, unexpected_keys, []
|
|
)
|
|
for k in missing_keys:
|
|
if "observer" in k or "activation_post_process" in k:
|
|
raise Exception(f"Missing keys for observer {k} in state_dict")
|
|
for k in unexpected_keys:
|
|
if "observer" in k or "activation_post_process" in k:
|
|
raise Exception(f"Unexpected keys for observer {k} in state_dict")
|
|
|
|
|
|
# Restrict activations to be in the range (0,127)
|
|
default_observer = MinMaxObserver.with_args(quant_min=0, quant_max=127)
|
|
"""
|
|
Default observer for static quantization, usually used for debugging.
|
|
"""
|
|
|
|
default_placeholder_observer = PlaceholderObserver
|
|
"""
|
|
Default placeholder observer, usually used for quantization to torch.float16.
|
|
"""
|
|
|
|
default_debug_observer = RecordingObserver
|
|
"""
|
|
Default debug-only observer.
|
|
"""
|
|
|
|
default_weight_observer = MinMaxObserver.with_args(
|
|
dtype=torch.qint8, qscheme=torch.per_tensor_symmetric
|
|
)
|
|
"""
|
|
Default weight observer.
|
|
"""
|
|
|
|
weight_observer_range_neg_127_to_127 = MinMaxObserver.with_args(
|
|
dtype=torch.qint8, qscheme=torch.per_tensor_symmetric,
|
|
quant_min=-127, quant_max=127, eps=2 ** -12)
|
|
"""
|
|
Symmetric weight observer with the 8-bit values restricted to [-127, +127], excluding -128.
|
|
"""
|
|
|
|
default_histogram_observer = HistogramObserver.with_args(quant_min=0, quant_max=127)
|
|
"""
|
|
Default histogram observer, usually used for PTQ.
|
|
"""
|
|
|
|
default_per_channel_weight_observer = PerChannelMinMaxObserver.with_args(
|
|
dtype=torch.qint8, qscheme=torch.per_channel_symmetric
|
|
)
|
|
"""
|
|
Default per-channel weight observer, usually used on backends where per-channel
|
|
weight quantization is supported, such as `fbgemm`.
|
|
"""
|
|
|
|
per_channel_weight_observer_range_neg_127_to_127 = PerChannelMinMaxObserver.with_args(
|
|
dtype=torch.qint8, qscheme=torch.per_channel_symmetric,
|
|
quant_min=-127, quant_max=127, eps=2 ** -12)
|
|
"""
|
|
Per-channel, symmetric weight observer with the 8-bit values restricted to [-127, +127], excluding -128.
|
|
"""
|
|
|
|
default_dynamic_quant_observer = PlaceholderObserver.with_args(
|
|
dtype=torch.quint8, quant_min=0, quant_max=255, is_dynamic=True,
|
|
)
|
|
"""
|
|
Default observer for dynamic quantization.
|
|
"""
|
|
|
|
default_float_qparams_observer = PerChannelMinMaxObserver.with_args(
|
|
dtype=torch.quint8, qscheme=torch.per_channel_affine_float_qparams, ch_axis=0
|
|
)
|
|
"""
|
|
Default observer for a floating point zero-point.
|
|
"""
|
|
|
|
default_float_qparams_observer_4bit = PerChannelMinMaxObserver.with_args(
|
|
dtype=torch.quint4x2, qscheme=torch.per_channel_affine_float_qparams, ch_axis=0
|
|
)
|
|
"""
|
|
Default observer for a floating point zero-point and 4 bit activations.
|
|
"""
|
|
|
|
# TODO(future PR): remove these defaults and enforce activation functions
|
|
# to explicitly specify their output range
|
|
default_fixed_qparams_range_neg1to1_observer = FixedQParamsObserver.with_args(
|
|
scale=2.0 / 256.0, zero_point=128, dtype=torch.quint8, quant_min=0, quant_max=255)
|
|
default_fixed_qparams_range_0to1_observer = FixedQParamsObserver.with_args(
|
|
scale=1.0 / 256.0, zero_point=0, dtype=torch.quint8, quant_min=0, quant_max=255)
|
|
# TODO: the following 2 variables are kept for backwards compatibility; remove after a few releases
|
|
default_symmetric_fixed_qparams_observer = default_fixed_qparams_range_neg1to1_observer
|
|
default_affine_fixed_qparams_observer = default_fixed_qparams_range_0to1_observer
|
|
|
|
"""
|
|
Default observers for fixed qparams operations.
|
|
"""
|
|
|
|
default_reuse_input_observer = ReuseInputObserver
|
|
"""
|
|
Default observer for operators like reshape that reuses the observer of input to
|
|
the operator
|
|
"""
|