import torch
import torch.nn as nn
import torch.nn.functional as F
import math
from . import base
from abc import abstractmethod
[文档]class StatelessEncoder(nn.Module):
def __init__(self):
"""
* :ref:`API in English <StatelessEncoder.__init__-en>`
.. _StatelessEncoder.__init__-cn:
无状态编码器的基类。无状态编码器 ``encoder = StatelessEncoder()``，直接调用 ``encoder(x)`` 即可将 ``x`` 编码为 ``spike``。
* :ref:`中文API <StatelessEncoder.__init__-cn>`
.. _StatelessEncoder.__init__-en:
The base class of stateless encoder. The stateless encoder ``encoder = StatelessEncoder()`` can encode ``x`` to
``spike`` by ``encoder(x)``.
"""
super().__init__()
[文档] @abstractmethod
def forward(self, x: torch.Tensor):
"""
* :ref:`API in English <StatelessEncoder.forward-en>`
.. _StatelessEncoder.forward-cn:
:param x: 输入数据
:type x: torch.Tensor
:return: ``spike``, shape 与 ``x.shape`` 相同
:rtype: torch.Tensor
* :ref:`中文API <StatelessEncoder.forward-cn>`
.. _StatelessEncoder.forward-en:
:param x: input data
:type x: torch.Tensor
:return: ``spike``, whose shape is same with ``x.shape``
:rtype: torch.Tensor
"""
raise NotImplementedError
[文档]class StatefulEncoder(base.MemoryModule):
def __init__(self, T: int):
"""
* :ref:`API in English <StatefulEncoder.__init__-en>`
.. _StatefulEncoder.__init__-cn:
:param T: 编码周期。通常情况下，与SNN的仿真周期（总步长一致）
:type T: int
有状态编码器的基类。有状态编码器 ``encoder = StatefulEncoder(T)``，编码器会在首次调用 ``encoder(x)`` 时对 ``x` 进行编码。在
第 ``t`` 次调用 ``encoder(x)`` 时会输出 ``spike[t % T]``
.. code-block:: python
encoder = StatefulEncoder(T)
s_list = []
for t in range(T):
s_list.append(encoder(x)) # s_list[t] == spike[t]
* :ref:`中文API <StatefulEncoder.__init__-cn>`
.. _StatefulEncoder.__init__-en:
:param T: the encoding period. It is usually same with the total simulation time-steps of SNN
:type T: int
The base class of stateful encoder. The stateful encoder ``encoder = StatefulEncoder(T)`` will encode ``x`` to
``spike`` at the first time of calling ``encoder(x)``. It will output ``spike[t % T]`` at the ``t`` -th calling
.. code-block:: python
encoder = StatefulEncoder(T)
s_list = []
for t in range(T):
s_list.append(encoder(x)) # s_list[t] == spike[t]
"""
super().__init__()
assert isinstance(T, int) and T >= 1
self.T = T
self.register_memory('spike', None)
self.register_memory('t', 0)
[文档] def forward(self, x: torch.Tensor = None):
"""
* :ref:`API in English <StatefulEncoder.forward-en>`
.. _StatefulEncoder.forward-cn:
:param x: 输入数据
:type x: torch.Tensor
:return: ``spike``, shape 与 ``x.shape`` 相同
:rtype: torch.Tensor
* :ref:`中文API <StatefulEncoder.forward-cn>`
.. _StatefulEncoder.forward-en:
:param x: input data
:type x: torch.Tensor
:return: ``spike``, whose shape is same with ``x.shape``
:rtype: torch.Tensor
"""
if self.spike is None:
self.encode(x)
t = self.t
self.t += 1
if self.t >= self.T:
self.t = 0
return self.spike[t]
[文档] @abstractmethod
def encode(self, x: torch.Tensor):
"""
* :ref:`API in English <StatefulEncoder.encode-en>`
.. _StatefulEncoder.encode-cn:
:param x: 输入数据
:type x: torch.Tensor
:return: ``spike``, shape 与 ``x.shape`` 相同
:rtype: torch.Tensor
* :ref:`中文API <StatefulEncoder.encode-cn>`
.. _StatefulEncoder.encode-en:
:param x: input data
:type x: torch.Tensor
:return: ``spike``, whose shape is same with ``x.shape``
:rtype: torch.Tensor
"""
raise NotImplementedError
[文档]class PeriodicEncoder(StatefulEncoder):
def __init__(self, spike: torch.Tensor):
"""
* :ref:`API in English <PeriodicEncoder.__init__-en>`
.. _PeriodicEncoder.__init__-cn:
:param spike: 输入脉冲
:type spike: torch.Tensor
周期性编码器，在第 ``t`` 次调用时输出 ``spike[t % T]``，其中 ``T = spike.shape[0]``
* :ref:`中文API <PeriodicEncoder.__init__-cn>`
.. _PeriodicEncoder.__init__-en:
:param spike: the input spike
:type spike: torch.Tensor
The periodic encoder that outputs ``spike[t % T]`` at ``t`` -th calling, where ``T = spike.shape[0]``
"""
super().__init__(spike.shape[0])
self.encode(spike)
[文档] def encode(self, spike: torch.Tensor):
self.spike = spike
self.T = spike.shape[0]
[文档]class LatencyEncoder(StatefulEncoder):
def __init__(self, T: int, enc_function='linear'):
"""
* :ref:`API in English <LatencyEncoder.__init__-en>`
.. _LatencyEncoder.__init__-cn:
:param T: 最大（最晚）脉冲发放时刻
:type T: int
:param enc_function: 定义使用哪个函数将输入强度转化为脉冲发放时刻，可以为 `linear` 或 `log`
:type enc_function: str
延迟编码器，将 ``0 <= x <= 1`` 的输入转化为在 ``0 <= t_f <= T-1`` 时刻发放的脉冲。输入的强度越大，发放越早。
当 ``enc_function == 'linear'``
.. math::
t_f(x) = (T - 1)(1 - x)
当 ``enc_function == 'log'``
.. math::
t_f(x) = (T - 1) - ln(\\alpha * x + 1)
其中 :math:`\alpha` 满足 :math:`t_f(1) = T - 1`
实例代码：
.. code-block:: python
x = torch.rand(size=[8, 2])
print('x', x)
T = 20
encoder = LatencyEncoder(T)
for t range(T):
print(encoder(x))
.. warning::
必须确保 ``0 <= x <= 1``。
* :ref:`中文API <LatencyEncoder.__init__-cn>`
.. _LatencyEncoder.__init__-en:
:param T: the maximum (latest) firing time
:type T: int
:param enc_function: how to convert intensity to firing time. `linear` or `log`
:type enc_function: str
The latency encoder will encode ``0 <= x <= 1`` to spike whose firing time is ``0 <= t_f <= T-1``. A larger
``x`` will cause a earlier firing time.
If ``enc_function == 'linear'``
.. math::
t_f(x) = (T - 1)(1 - x)
If ``enc_function == 'log'``
.. math::
t_f(x) = (T - 1) - ln(\\alpha * x + 1)
where :math:`\alpha` satisfies :math:`t_f(1) = T - 1`
Example:
.. code-block:: python
x = torch.rand(size=[8, 2])
print('x', x)
T = 20
encoder = LatencyEncoder(T)
for t range(T):
print(encoder(x))
.. admonition:: Warning
:class: warning
The user must assert ``0 <= x <= 1``.
"""
super().__init__(T)
if enc_function == 'log':
self.alpha = math.exp(T - 1.) - 1.
elif enc_function != 'linear':
raise NotImplementedError
self.enc_function = enc_function
[文档] def encode(self, x: torch.Tensor):
if self.enc_function == 'log':
t_f = (self.T - 1. - torch.log(self.alpha * x + 1.)).round().long()
else:
t_f = ((self.T - 1.) * (1. - x)).round().long()
self.spike = F.one_hot(t_f, num_classes=self.T).to(x)
# [*, T] -> [T, *]
d_seq = list(range(self.spike.ndim - 1))
d_seq.insert(0, self.spike.ndim - 1)
self.spike = self.spike.permute(d_seq)
[文档]class PoissonEncoder(StatelessEncoder):
def __init__(self):
"""
* :ref:`API in English <PoissonEncoder.__init__-en>`
.. _PoissonEncoder.__init__-cn:
无状态的泊松编码器。输出脉冲的发放概率与输入 ``x`` 相同。
.. warning::
必须确保 ``0 <= x <= 1``。
* :ref:`中文API <PoissonEncoder.__init__-cn>`
.. _PoissonEncoder.__init__-en:
The poisson encoder will output spike whose firing probability is ``x``。
.. admonition:: Warning
:class: warning
The user must assert ``0 <= x <= 1``.
"""
super().__init__()
[文档] def forward(self, x: torch.Tensor):
out_spike = torch.rand_like(x).le(x).to(x)
return out_spike
[文档]class WeightedPhaseEncoder(StatefulEncoder):
def __init__(self, K: int):
"""
* :ref:`API in English <WeightedPhaseEncoder.__init__-en>`
.. _WeightedPhaseEncoder.__init__-cn:
:param K: 编码周期。通常情况下，与SNN的仿真周期（总步长一致）
:type K: int
Kim J, Kim H, Huh S, et al. Deep neural networks with weighted spikes[J]. Neurocomputing, 2018, 311: 373-386.
带权的相位编码，一种基于二进制表示的编码方法。
将输入按照二进制各位展开，从高位到低位遍历输入进行脉冲编码。相比于频率编码，每一位携带的信息量更多。编码相位数为 :math:`K` 时，
可以对于处于区间 :math:`[0, 1-2^{-K}]` 的数进行编码。以下为原始论文中的示例：
+----------------------------------+----------------+----------------+----------------+----------------+----------------+----------------+----------------+----------------+
| Phase (K=8) | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 |
+==================================+================+================+================+================+================+================+================+================+
| Spike weight :math:`\omega(t)` | 2\ :sup:`-1` | 2\ :sup:`-2` | 2\ :sup:`-3` | 2\ :sup:`-4` | 2\ :sup:`-5` | 2\ :sup:`-6` | 2\ :sup:`-7` | 2\ :sup:`-8` |
+----------------------------------+----------------+----------------+----------------+----------------+----------------+----------------+----------------+----------------+
| 192/256 | 1 | 1 | 0 | 0 | 0 | 0 | 0 | 0 |
+----------------------------------+----------------+----------------+----------------+----------------+----------------+----------------+----------------+----------------+
| 1/256 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 |
+----------------------------------+----------------+----------------+----------------+----------------+----------------+----------------+----------------+----------------+
| 128/256 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
+----------------------------------+----------------+----------------+----------------+----------------+----------------+----------------+----------------+----------------+
| 255/256 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 |
+----------------------------------+----------------+----------------+----------------+----------------+----------------+----------------+----------------+----------------+
* :ref:`中文API <WeightedPhaseEncoder.__init__-cn>`
.. _WeightedPhaseEncoder.__init__-en:
:param K: the encoding period. It is usually same with the total simulation time-steps of SNN
:type K: int
The weighted phase encoder, which is based on binary system. It will flatten ``x`` as a binary number. When
``T=k``, it can encode :math:`x \in [0, 1-2^{-K}]` to different spikes. Here is the example from the origin paper:
+----------------------------------+----------------+----------------+----------------+----------------+----------------+----------------+----------------+----------------+
| Phase (K=8) | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 |
+==================================+================+================+================+================+================+================+================+================+
| Spike weight :math:`\omega(t)` | 2\ :sup:`-1` | 2\ :sup:`-2` | 2\ :sup:`-3` | 2\ :sup:`-4` | 2\ :sup:`-5` | 2\ :sup:`-6` | 2\ :sup:`-7` | 2\ :sup:`-8` |
+----------------------------------+----------------+----------------+----------------+----------------+----------------+----------------+----------------+----------------+
| 192/256 | 1 | 1 | 0 | 0 | 0 | 0 | 0 | 0 |
+----------------------------------+----------------+----------------+----------------+----------------+----------------+----------------+----------------+----------------+
| 1/256 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 |
+----------------------------------+----------------+----------------+----------------+----------------+----------------+----------------+----------------+----------------+
| 128/256 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
+----------------------------------+----------------+----------------+----------------+----------------+----------------+----------------+----------------+----------------+
| 255/256 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 |
+----------------------------------+----------------+----------------+----------------+----------------+----------------+----------------+----------------+----------------+
"""
super().__init__(K)
[文档] def encode(self, x: torch.Tensor):
assert (x >= 0).all() and (x <= 1 - 2 ** (-self.T)).all()
inputs = x.clone()
self.spike = torch.empty((self.T,) + x.shape, device=x.device) # Encoding to [T, batch_size, *]
w = 0.5
for i in range(self.T):
self.spike[i] = inputs >= w
inputs -= w * self.spike[i]
w *= 0.5