| from __future__ import absolute_import, division, print_function, unicode_literals |
| |
| import math |
| import warnings |
| from abc import ABCMeta, abstractmethod |
| from functools import partial |
| |
| import torch |
| import torch.nn as nn |
| from torch._jit_internal import List, Optional |
| |
| def _with_args(cls_or_self, **kwargs): |
| r"""Wrapper that allows creation of class factories. |
| |
| This can be useful when there is a need to create classes with the same |
| constructor arguments, but different instances. |
| |
| .. Example:: |
| |
| >>> Foo.with_args = classmethod(_with_args) |
| >>> foo_builder = Foo.with_args(a=3, b=4).with_args(answer=42) |
| >>> foo_instance1 = foo_builder() |
| >>> foo_instance2 = foo_builder() |
| >>> id(foo_instance1) == id(foo_instance2) |
| False |
| """ |
| class _PartialWrapper(object): |
| def __init__(self, p): |
| self.p = p |
| |
| def __call__(self, *args, **keywords): |
| return self.p(*args, **keywords) |
| |
| def __repr__(self): |
| return self.p.__repr__() |
| |
| with_args = _with_args |
| r = _PartialWrapper(partial(cls_or_self, **kwargs)) |
| return r |
| |
| |
| ABC = ABCMeta(str("ABC"), (object,), {}) # compatible with Python 2 *and* 3: |
| |
| |
| class ObserverBase(ABC, nn.Module): |
| r"""Base observer Module. |
| Any observer implementation should derive from this class. |
| |
| Concrete observers should follow the same API. In forward, they will update |
| the statistics of the observed Tensor. And they should provide a |
| `calculate_qparams` function that computes the quantization parameters given |
| the collected statistics. |
| |
| Args: |
| dtype: Quantized data type |
| """ |
| def __init__(self, dtype): |
| super(ObserverBase, self).__init__() |
| self.dtype = dtype |
| |
| @abstractmethod |
| def forward(self, x): |
| pass |
| |
| @abstractmethod |
| def calculate_qparams(self, **kwargs): |
| pass |
| |
| with_args = classmethod(_with_args) |
| |
| |
| class _ObserverBase(ObserverBase): |
| r"""Internal common base for all qint/quint8 observers. |
| |
| This base is for commonly used paramters used internally. |
| Users should use `~torch.quantization.observer.ObserverBase` as a base class |
| for custom observers. |
| |
| Args: |
| dtype: Quantized data type. |
| qscheme: Quantization scheme to be used. |
| reduce_range: Reduces the range of the quantized data type by 1 bit. |
| This is sometimes required to avoid instruction overflow. |
| |
| .. warning:: |
| |
| :attr:`dtype` can only take ``torch.qint8`` or ``torch.quint8``. |
| |
| .. warning:: |
| |
| :attr:`qscheme` can only take one of the following options: |
| |
| - ``torch.per_tensor_affine`` |
| - ``torch.per_tensor_symmetric`` |
| - ``torch.per_channel_affine`` |
| - ``torch.per_channel_symmetric`` |
| """ |
| |
| def __init__(self, dtype=torch.quint8, qscheme=torch.per_tensor_affine, |
| reduce_range=False): |
| super(_ObserverBase, self).__init__(dtype=dtype) |
| self.qscheme = qscheme |
| self.reduce_range = reduce_range |
| |
| self.eps = torch.finfo(torch.float32).eps |
| assert self.qscheme in ( |
| torch.per_tensor_affine, |
| torch.per_tensor_symmetric, |
| torch.per_channel_affine, |
| torch.per_channel_symmetric, |
| ), "Default Observer only works for per_tensor_affine, \ |
| per_tensor_symmetric, per_channel_affine and \ |
| per_channel_symmetric quantization scheme" |
| assert self.dtype in ( |
| torch.qint8, |
| torch.quint8, |
| ), "Default Observer only works for qint8 and quint8 data type" |
| |
| def _calculate_per_channel_qparams(self, min_vals, max_vals): |
| # type: (Optional[Tensor], Optional[Tensor]) -> Tuple[Tensor, Tensor] |
| r"""Calculates the per channel quantization parameters, given min and max |
| value tensors. |
| |
| Args: |
| min_vals: Minimum values per channel |
| max_vals: Maximum values per channel |
| |
| Returns: |
| scales: Per channel scales tensor of shape (#channels,) |
| zero_points: Per channel zero points tensor of shape (#channels,) |
| """ |
| if min_vals is None or max_vals is None: |
| warnings.warn( |
| "must run observer before calling calculate_qparams.\ |
| Returning default scale and zero point " |
| ) |
| return torch.tensor([1.0]), torch.tensor([0]) |
| |
| for i in range(len(min_vals)): |
| assert ( |
| min_vals[i] <= max_vals[i] |
| ), "min {} should be less than max {}".format(min_vals[i], max_vals[i]) |
| |
| scales = torch.empty(min_vals.size(), dtype=torch.float32) |
| zero_points = torch.empty(min_vals.size(), dtype=torch.int64) |
| |
| for i in range(len(scales)): |
| qparam = self._calculate_qparams( |
| min_vals[i], max_vals[i] |
| ) |
| scales[i] = float(qparam[0]) |
| zero_points[i] = int(qparam[1]) |
| |
| return scales, zero_points |
| |
| def _calculate_qparams(self, min_val, max_val): |
| # type: (Optional[Tensor], Optional[Tensor]) -> Tuple[Tensor, Tensor] |
| r"""Calculates the per tensor quantization parameters, given the min/max. |
| |
| Args: |
| min_val: Per tensor minimum value |
| max_val: Per tensor maximum value |
| |
| Returns: |
| scale: Scale as a tensor of shape (1,) |
| zero_point: Zero point as a tensor of shape (1,) |
| """ |
| |
| if max_val is None or min_val is None: |
| warnings.warn("Must run observer before calling calculate_qparams.\ |
| Returning default scale and zero point.") |
| return torch.tensor([1.0]), torch.tensor([0]) |
| |
| assert min_val <= max_val, "min {} should be less than max {}".format( |
| min_val, max_val |
| ) |
| |
| if self.dtype == torch.qint8: |
| if self.reduce_range: |
| qmin, qmax = -64, 63 |
| else: |
| qmin, qmax = -128, 127 |
| else: |
| if self.reduce_range: |
| qmin, qmax = 0, 127 |
| else: |
| qmin, qmax = 0, 255 |
| |
| max_val, min_val = float(max_val), float(min_val) |
| min_val = min(0.0, min_val) |
| max_val = max(0.0, max_val) |
| if max_val == min_val: |
| scale = 1.0 |
| zero_point = 0 |
| else: |
| if self.qscheme == torch.per_tensor_symmetric or self.qscheme == torch.per_channel_symmetric: |
| max_val = max(-min_val, max_val) |
| scale = max_val / ((qmax - qmin) / 2) |
| scale = max(scale, self.eps) |
| zero_point = 0 if self.dtype == torch.qint8 else 128 |
| else: |
| scale = (max_val - min_val) / float(qmax - qmin) |
| scale = max(scale, self.eps) |
| zero_point = qmin - round(min_val / scale) |
| zero_point = max(qmin, zero_point) |
| zero_point = min(qmax, zero_point) |
| zero_point = int(zero_point) |
| |
| return torch.tensor([scale]), torch.tensor([zero_point]) |
| |
| |
| class MinMaxObserver(_ObserverBase): |
| 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: Quantized data type |
| qscheme: Quantization scheme to be used |
| reduce_range: Reduces the range of the quantized data type by 1 bit |
| |
| 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:: Only works with ``torch.per_tensor_symmetric`` quantization scheme |
| |
| .. 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. |
| """ |
| |
| __annotations__ = { |
| "min_val": Optional[torch.Tensor], |
| "max_val": Optional[torch.Tensor], |
| } |
| |
| def __init__(self, dtype=torch.quint8, qscheme=torch.per_tensor_affine, |
| reduce_range=False): |
| # 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(MinMaxObserver, self).__init__(dtype=dtype, |
| qscheme=qscheme, |
| reduce_range=reduce_range) |
| self.min_val = None |
| self.max_val = None |
| 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``.""" |
| x = x_orig.detach() |
| min_val = self.min_val |
| max_val = self.max_val |
| if min_val is None or max_val is None: |
| min_val = torch.min(x) |
| max_val = torch.max(x) |
| else: |
| min_val = torch.min(torch.min(x), min_val) |
| max_val = torch.max(torch.max(x), max_val) |
| self.min_val = min_val |
| self.max_val = 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 "min_val={}, max_val={}".format(self.min_val, self.max_val) |
| |
| def _save_to_state_dict(self, destination, prefix, keep_vars): |
| super(MinMaxObserver, self)._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): |
| |
| self.min_val = state_dict.pop(prefix + 'min_val') |
| self.max_val = state_dict.pop(prefix + 'max_val') |
| super(MinMaxObserver, self)._load_from_state_dict(state_dict, prefix, local_metadata, False, |
| missing_keys, unexpected_keys, error_msgs) |
| |
| |
| 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: Quantized data type |
| qscheme: Quantization scheme to be used |
| reduce_range: Reduces the range of the quantized data type by 1 bit |
| |
| 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.quantization.observer.MinMaxObserver`. |
| |
| .. note:: Only works with ``torch.per_tensor_affine`` quantization shceme. |
| |
| .. 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): |
| self.averaging_constant = averaging_constant |
| super(MovingAverageMinMaxObserver, self).__init__(dtype=dtype, |
| qscheme=qscheme, |
| reduce_range=reduce_range) |
| |
| def forward(self, x_orig): |
| x = x_orig.detach() # avoid keeping autograd tape |
| min_val = self.min_val |
| max_val = self.max_val |
| if min_val is None or max_val is None: |
| min_val = torch.min(x) |
| max_val = torch.max(x) |
| else: |
| min_val = min_val + self.averaging_constant * (torch.min(x) - min_val) |
| max_val = max_val + self.averaging_constant * (torch.max(x) - max_val) |
| self.min_val = min_val |
| self.max_val = max_val |
| return x_orig |
| |
| |
| class PerChannelMinMaxObserver(_ObserverBase): |
| 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: Quantized data type |
| qscheme: Quantization scheme to be used |
| reduce_range: Reduces the range of the quantized data type by 1 bit |
| |
| The quantization parameters are computed the same way as in |
| :class:`~torch.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. |
| """ |
| |
| def __init__(self, ch_axis=0, dtype=torch.quint8, |
| qscheme=torch.per_tensor_affine, reduce_range=False): |
| super(PerChannelMinMaxObserver, self).__init__(dtype=dtype, |
| qscheme=qscheme, |
| reduce_range=reduce_range) |
| self.ch_axis = ch_axis |
| self.register_buffer('min_vals', None) |
| self.register_buffer('max_vals', None) |
| 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): |
| x = x_orig.detach() # avoid keeping autograd tape |
| min_vals = self.min_vals |
| max_vals = self.max_vals |
| x_dim = x.size() |
| |
| new_axis_list = list(range(len(x_dim))) |
| new_axis_list[self.ch_axis] = 0 |
| new_axis_list[0] = self.ch_axis |
| y = x.permute(tuple(new_axis_list)) |
| y = torch.flatten(y, start_dim=1) |
| if min_vals is None or max_vals is None: |
| min_vals = torch.min(y, 1)[0] |
| max_vals = torch.max(y, 1)[0] |
| else: |
| min_vals = torch.min(torch.min(y, 1)[0], min_vals) |
| max_vals = torch.max(torch.max(y, 1)[0], max_vals) |
| self.min_vals = min_vals |
| self.max_vals = max_vals |
| return x_orig |
| |
| def calculate_qparams(self): |
| return self._calculate_per_channel_qparams(self.min_vals, self.max_vals) |
| |
| def extra_repr(self): |
| return "min_val={}, max_val={}".format(self.min_vals, self.max_vals) |
| |
| def _load_from_state_dict(self, state_dict, prefix, local_metadata, strict, |
| missing_keys, unexpected_keys, error_msgs): |
| # We have to handle min_vals and max_vals manually even though they are registered as buffers |
| # as they are initialized to None |
| self.min_vals = state_dict.pop(prefix + 'min_vals') |
| self.max_vals = state_dict.pop(prefix + 'max_vals') |
| super(PerChannelMinMaxObserver, self)._load_from_state_dict(state_dict, prefix, local_metadata, False, |
| missing_keys, unexpected_keys, error_msgs) |
| |
| 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 |
| |
| The quantization parameters are computed the same way as in |
| :class:`~torch.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_tensor_affine, reduce_range=False): |
| super(MovingAveragePerChannelMinMaxObserver, self).__init__( |
| ch_axis=ch_axis, dtype=dtype, qscheme=qscheme, |
| reduce_range=reduce_range) |
| self.averaging_constant = averaging_constant |
| |
| def forward(self, x_orig): |
| x = x_orig.detach() # avoid keeping autograd tape |
| min_vals = self.min_vals |
| max_vals = self.max_vals |
| x_dim = x.size() |
| |
| new_axis_list = list(range(len(x_dim))) |
| new_axis_list[self.ch_axis] = 0 |
| new_axis_list[0] = self.ch_axis |
| y = x.permute(tuple(new_axis_list)) |
| y = torch.flatten(y, start_dim=1) |
| if min_vals is None or max_vals is None: |
| min_vals = torch.min(y, 1)[0] |
| max_vals = torch.max(y, 1)[0] |
| else: |
| min_vals = min_vals + self.averaging_constant * (torch.min(y, 1)[0] - min_vals) |
| max_vals = max_vals + self.averaging_constant * (torch.max(y, 1)[0] - max_vals) |
| self.min_vals = min_vals |
| self.max_vals = max_vals |
| return x_orig |
| |
| class HistogramObserver(_ObserverBase): |
| 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 |
| dtype: Quantized data type |
| qscheme: Quantization scheme to be used |
| reduce_range: Reduces the range of the quantized data type by 1 bit |
| |
| 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.quantization.MinMaxObserver` |
| """ |
| |
| __annotations__ = { |
| "min_val": Optional[torch.Tensor], |
| "max_val": Optional[torch.Tensor], |
| } |
| |
| def __init__(self, bins=2048, dtype=torch.quint8, |
| qscheme=torch.per_tensor_affine, reduce_range=False): |
| # bins: The number of bins used for histogram calculation. |
| super(HistogramObserver, self).__init__(dtype=dtype, |
| qscheme=qscheme, |
| reduce_range=reduce_range) |
| self.bins = bins |
| self.register_buffer('histogram', torch.zeros(self.bins)) |
| self.min_val = None |
| self.max_val = None |
| |
| @staticmethod |
| def _get_norm(delta_begin, delta_end, density, norm_type): |
| r""" |
| Compute the norm of the values uniformaly distributed between |
| delta_begin and delta_end. |
| |
| norm = density * (integral_{begin, end} x^2) |
| = density * (end^3 - begin^3) / 3 |
| """ |
| assert norm_type == "L2", "Only L2 norms are currently supported" |
| norm = 0.0 |
| if norm_type == "L2": |
| 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, next_end_bin, norm_type): |
| r""" |
| Compute the quantization error if we use start_bin to end_bin as the |
| min and max to do the quantization. |
| """ |
| dst_nbins = 2 ** torch.iinfo(self.dtype).bits |
| bin_width = (self.max_val.item() - self.min_val.item()) / self.bins |
| |
| norm = 0.0 |
| dst_bin_width = bin_width * (next_end_bin - next_start_bin + 1) / dst_nbins |
| if dst_bin_width == 0.0: |
| return 0.0 |
| for src_bin in range(self.bins): |
| # 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 = min( |
| dst_nbins - 1, max(0.0, math.floor(src_bin_begin / dst_bin_width)) |
| ) |
| dst_bin_of_end = min( |
| dst_nbins - 1, max(0.0, math.floor(src_bin_end / dst_bin_width)) |
| ) |
| dst_bin_of_begin_center = ( |
| dst_bin_of_begin * dst_bin_width + dst_bin_width / 2 |
| ) |
| |
| density = self.histogram[src_bin] / bin_width |
| if dst_bin_of_begin == dst_bin_of_end: |
| # if src_bin is entirely within 1 dst_bin |
| delta_begin = src_bin_begin - dst_bin_of_begin_center |
| delta_end = src_bin_end - dst_bin_of_begin_center |
| norm = norm + self._get_norm(delta_begin, delta_end, density, norm_type) |
| else: |
| delta_begin = src_bin_begin - dst_bin_of_begin_center |
| delta_end = dst_bin_width / 2 |
| norm = norm + self._get_norm(delta_begin, delta_end, density, norm_type) |
| |
| norm = norm + (dst_bin_of_end - dst_bin_of_begin - 1) * self._get_norm( |
| -dst_bin_width / 2, dst_bin_width / 2, density, norm_type |
| ) |
| |
| 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 = norm + self._get_norm(delta_begin, delta_end, density, norm_type) |
| return norm |
| |
| def _non_linear_param_search(self): |
| 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 mistmatch" |
| bin_width = (self.max_val - self.min_val) / self.bins |
| |
| # cumulative sum |
| total = sum(self.histogram) |
| 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, "L2") |
| |
| 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 _combine_histograms( |
| self, dst_histogram, dst_min, dst_max, src_histogram, src_min, src_max |
| ): |
| bins_dst = dst_histogram.size()[0] |
| bins_src = src_histogram.size()[0] |
| |
| dst_bin_width = (dst_max - dst_min) / bins_dst |
| src_bin_width = (src_max - src_min) / bins_src |
| |
| for i in range(bins_src): |
| src_bin_count = src_histogram[i].item() |
| if src_bin_count == 0: |
| continue |
| |
| src_bin_begin = src_min + src_bin_width * i |
| src_bin_end = src_bin_begin + src_bin_width |
| |
| dst_bin = 0 |
| if dst_bin_width: |
| dst_bin = int((src_bin_begin - dst_min) / dst_bin_width) |
| |
| dst_bin_begin = dst_min + dst_bin_width * dst_bin |
| dst_bin_end = dst_bin_begin + dst_bin_width |
| |
| dst_bin2 = 0 |
| if dst_bin_width: |
| dst_bin2 = min( |
| int((src_bin_end - dst_min) / dst_bin_width), bins_dst - 1 |
| ) |
| |
| assert dst_bin2 <= dst_bin + 2, "1 src_bin is mapped to at most 2 dst_bins" |
| # dst_bin_cnt is the count from src_bin that should go to dst_bin |
| # the remainder should go to dst_bin2 |
| dst_bin_cnt = 0 |
| if src_bin_width == 0 or dst_bin_width == 0: |
| dst_bin_cnt = src_bin_count |
| else: |
| # We divide counts in src_bin in proportion to range overlap with dst_bin |
| dst_bin_cnt = min( |
| round( |
| (dst_bin_end - src_bin_begin) / src_bin_width * src_bin_count |
| ), |
| src_bin_count, |
| ) |
| |
| dst_histogram[dst_bin] += dst_bin_cnt |
| |
| # remaining should go to dst_bin2 |
| if dst_bin_cnt < src_bin_count: |
| dst_histogram[dst_bin2] += src_bin_count - dst_bin_cnt |
| |
| def forward(self, x): |
| with torch.no_grad(): |
| min_val = self.min_val |
| max_val = self.max_val |
| if min_val is None or max_val is None: |
| min_val = torch.min(x) |
| max_val = torch.max(x) |
| self.min_val = min_val |
| self.max_val = max_val |
| self.histogram = torch.histc(x, self.bins, min=min_val, max=max_val) |
| else: |
| new_min = torch.min(x) |
| new_max = torch.max(x) |
| new_histogram = torch.histc(x, self.bins, min=new_min, max=new_max) |
| # combine the existing histogram and new histogram into 1 histogram |
| combined_histogram = torch.zeros_like(self.histogram) |
| combined_min = torch.min(new_min, self.min_val) |
| combined_max = torch.max(new_max, self.max_val) |
| self._combine_histograms( |
| combined_histogram, |
| combined_min.item(), |
| combined_max.item(), |
| self.histogram, |
| self.min_val.item(), |
| self.max_val.item(), |
| ) |
| self._combine_histograms( |
| combined_histogram, |
| combined_min.item(), |
| combined_max.item(), |
| new_histogram, |
| new_min.item(), |
| new_max.item(), |
| ) |
| self.histogram = combined_histogram |
| self.min_val = combined_min |
| self.max_val = combined_max |
| return x |
| |
| def calculate_qparams(self): |
| if self.min_val is None or self.max_val is None: |
| warnings.warn( |
| "must run observer before calling calculate_qparams.\ |
| Returning default scale and zero point " |
| ) |
| return torch.tensor([1.0]), torch.tensor([0]) |
| 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.item(), new_max.item()) |
| |
| def _save_to_state_dict(self, destination, prefix, keep_vars): |
| super(HistogramObserver, self)._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): |
| self.min_val = state_dict.pop(prefix + 'min_val') |
| self.max_val = state_dict.pop(prefix + 'max_val') |
| super(HistogramObserver, self)._load_from_state_dict(state_dict, prefix, local_metadata, False, |
| missing_keys, unexpected_keys, error_msgs) |
| |
| 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, **kwargs): |
| super(RecordingObserver, self).__init__(**kwargs) |
| 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 |
| """ |
| def __init__(self, dtype=torch.float16): |
| if dtype != torch.float16: |
| raise ValueError("Only float16 quantization can be used without calibration process") |
| super(NoopObserver, self).__init__(dtype=dtype) |
| |
| def forward(self, x): |
| return x |
| |
| def calculate_qparams(self): |
| raise Exception("calculate_qparams should not be called for NoopObserver") |
| |
| |
| # Restrict activations to be in the range (0,127) |
| default_observer = MinMaxObserver.with_args(reduce_range=True) |
| default_debug_observer = RecordingObserver |
| default_weight_observer = MinMaxObserver.with_args(dtype=torch.qint8, qscheme=torch.per_tensor_symmetric) |
| default_histogram_observer = HistogramObserver.with_args(reduce_range=True) |
| default_per_channel_weight_observer = PerChannelMinMaxObserver.with_args(dtype=torch.qint8, qscheme=torch.per_channel_symmetric) |
