wehub-resource-sync
32 lines
748 B
Python
Executable File
32 lines
748 B
Python
Executable File
import numpy as np
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from prml.nn.tensor.constant import Constant
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from prml.nn.tensor.tensor import Tensor
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from prml.nn.function import Function
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class Sigmoid(Function):
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"""
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logistic sigmoid function
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y = 1 / (1 + exp(-x))
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"""
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def forward(self, x):
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x = self._convert2tensor(x)
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self.x = x
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self.output = np.tanh(x.value * 0.5) * 0.5 + 0.5
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if isinstance(self.x, Constant):
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return Constant(self.output)
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return Tensor(self.output, function=self)
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def backward(self, delta):
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dx = self.output * (1 - self.output) * delta
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self.x.backward(dx)
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def sigmoid(x):
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"""
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logistic sigmoid function
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y = 1 / (1 + exp(-x))
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"""
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return Sigmoid().forward(x)
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