January 2017
Beginner to intermediate
312 pages
7h 3m
Korean
Content preview from 밑바닥부터 시작하는 딥러닝
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294
밑바닥부터 시작하는 딥러닝
A.2
역전파
우선
Cross
Entropy
Error
계층의 역전파입니다. 이 계층의 역전파는 [그림
A
-
4
]처럼 그릴
수 있습니다.
그림
A-4
Cross
Entropy
Error
계층의 역전파
이 계산 그래프의 역전파를 구할 때는 다음을 조심해야 합니다.
●
역전파의 초깃값, 즉 [그림
A
-
4
]의 가장 오른쪽 역전파의 값은
1
이다 ( =
1
이므로 ).
●
‘×’ 노드의 역전파는 순전파 시의 입력들의 값을 ‘서로 바꿔’
*
상류의 미분에 곱하고 하류로 흘린다.
●
‘+’ 노드에서는 상류에서 전해지는 미분을 그대로 흘린다.
●
‘
log
’ 노드의 역전파는 다음 식을 따른다.
y
=
log
x
2
y
2
x
=
1
x
이상의 규칙을 따르면
Cross
Entropy
Error
계층의 역전파는 쉽게 구할 수 있습니다. 결과는
이며, 이 값이
Softmax
계층으로의 역전파 입력이 됩니다.
이어서
Softmax
계층의 역전파입니다. 이 계층의 역전파는 조금 복잡하니 하나씩 확인하면서
진행해보겠습니다.
*
옮긴이_ 가장 오른쪽 ‘×’ 노드를 예로 보면, 순전파 때의 입력은
t
1
log
y
1
+
t
2
log
y
2
+
t
3
log
y
3
와 -
1
입니다. 여기서 ‘서로 바꾼다’는 것
은 이 두 입력을 바꾼다는 뜻입니다.
2
L
2
L
y
t
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O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.Julian F.
I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.