오차역전파법을 위한 덧셈층, 곱셈층

pydl_backpropagation_layer1.py

class AddLayer:
    def __init__(self):
        pass
    def forward(self, x, y):
        return x + y
    def backward(self, dout):
        dx = dout * 1
        dy = dout * 1
        return dx, dy

class MulLayer:
    def __init__(self):
        self.x = None
        self.y = None
    def forward(self, x, y):
        self.x = x
        self.y = y
        return x * y
    def backward(self, dout):
        dx = dout * self.y
        dy = dout * self.x
        return dx, dy

apple_price = 100
apple_num = 2
orange_price = 150
orange_num = 3
tax = 1.1

print( "사과값:", apple_price ) # 100
print( "사과개수:", apple_num ) # 2
print( "오렌지값:", orange_price ) # 150
print( "오렌지개수:", orange_num ) # 3
print( "세금:", tax ) # 1.1

apple_mul_layer = MulLayer()
orange_mul_layer = MulLayer()
add_apple_orange_layer = AddLayer()
tax_mul_layer = MulLayer()

apple_total_price = apple_mul_layer.forward(apple_price, apple_num)
orange_total_price = orange_mul_layer.forward(orange_price, orange_num)
total_price = add_apple_orange_layer.forward(apple_total_price, orange_total_price)
tax_price = tax_mul_layer.forward(total_price, tax)

print( "세전가:", total_price ) # 650
print( "세후가:", tax_price ) # 715

d_price = 1
d_all_price, d_tax = tax_mul_layer.backward(d_price)
d_apple_price, d_orange_price = add_apple_orange_layer.backward(d_all_price)
d_apple, d_apple_num = apple_mul_layer.backward(d_apple_price)
d_orange, d_orange_num = orange_mul_layer.backward(d_orange_price)

print( "세후가/세전가 미분:", d_all_price ) # 1.1
print( "세후가/세금 미분:", d_tax ) # 650
print( "세후가/전체사과값 미분:", d_apple_price ) # 1.1
print( "세후가/전체오렌지값 미분:", d_orange_price ) # 1.1
print( "세후가/사과값 미분:", d_apple ) # 2.2
print( "세후가/사과개수 미분:", d_apple_num ) # 110
print( "세후가/오렌지값 미분:", d_orange ) # 3.3
print( "세후가/오렌지개수 미분:", d_orange_num ) # 165