In [9]:

    

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


    

In [10]:

    

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


    

In [11]:

    

apple = 100
apple_num = 2
tax = 1.1

# layer
mul_apple_layer = MulLayer()
mul_tax_layer = MulLayer()

# Forward
apple_price = mul_apple_layer.forward(apple, apple_num)
price = mul_tax_layer.forward(apple_price, tax)

print(price)

# Backward
dprice = 1
dapple_price, dtax = mul_tax_layer.backward(dprice)
dapple, dapple_num = mul_apple_layer.backward(dapple_price)

print(dapple, dapple_num, dtax)


    

    




220.00000000000003
2.2 110.00000000000001 200

In [12]:

    

apple = 100
apple_num = 2
orange = 150
orange_num = 3
tax = 1.1

# layer
mul_apple_layer = MulLayer()
mul_orange_layer = MulLayer()
add_apple_orange_layer = AddLayer()
mul_tax_layer = MulLayer()

# Forward
apple_price = mul_apple_layer.forward(apple, apple_num)
orange_price = mul_orange_layer.forward(orange, orange_num)
all_price = add_apple_orange_layer.forward(apple_price, orange_price)
price = mul_tax_layer.forward(all_price, tax)

print(price)

# Backward
dprice = 1
dall_price, dtax = mul_tax_layer.backward(dprice)
dapple_price, dorange_price = add_apple_orange_layer.backward(dall_price)
dorange, dorange_num = mul_orange_layer.backward(dorange_price)
dapple, dapple_num = mul_apple_layer.backward(dapple_price)

print(dapple, dapple_num, dorange, dorange_num, dtax)


    

    




715.0000000000001
2.2 110.00000000000001 3.3000000000000003 165.0 650