DL之DNN:自定义2层神经网络TwoLayerNet模型(封装为层级结构)利用MNIST数据集进行训练、预测
导读
计算图在神经网络算法中的作用。计算图的节点是由局部计算构成的。局部计算构成全局计算。计算图的正向传播进行一般的计算。通过计算图的反向传播,可以计算各个节点的导数。
目录
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- class TwoLayerNet:
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- def __init__(self, input_size, hidden_size, output_size, weight_init_std = 0.01):
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- self.params = {}
- self.params['W1'] = weight_init_std * np.random.randn(input_size, hidden_size)
- self.params['b1'] = np.zeros(hidden_size)
- self.params['W2'] = weight_init_std * np.random.randn(hidden_size, output_size)
- self.params['b2'] = np.zeros(output_size)
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- self.layers = OrderedDict()
- self.layers['Affine1'] = Affine(self.params['W1'], self.params['b1'])
- self.layers['Relu1'] = Relu()
- self.layers['Affine2'] = Affine(self.params['W2'], self.params['b2'])
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- self.lastLayer = SoftmaxWithLoss()
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- def predict(self, x):
- for layer in self.layers.values():
- x = layer.forward(x)
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- return x
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- x:输入数据, t:监督数据
- def loss(self, x, t):
- y = self.predict(x)
- return self.lastLayer.forward(y, t)
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- def accuracy(self, x, t):
- y = self.predict(x)
- y = np.argmax(y, axis=1)
- if t.ndim != 1 : t = np.argmax(t, axis=1)
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- accuracy = np.sum(y == t) / float(x.shape[0])
- return accuracy
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-
- def gradient(self, x, t):
- self.loss(x, t)
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- dout = 1
- dout = self.lastLayer.backward(dout)
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- layers = list(self.layers.values())
- layers.reverse()
- for layer in layers:
- dout = layer.backward(dout)
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- grads = {}
- grads['W1'], grads['b1'] = self.layers['Affine1'].dW, self.layers['Affine1'].db
- grads['W2'], grads['b2'] = self.layers['Affine2'].dW, self.layers['Affine2'].db
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- return grads
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