January 2017
Beginner to intermediate
312 pages
7h 3m
Korean
Content preview from 밑바닥부터 시작하는 딥러닝
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170
밑바닥부터 시작하는 딥러닝
그림
5-22
Sigmoid
계층의 계산 그래프 : 순전파의 출력
y
만으로 역전파를 계산할 수 있다.
그럼
Sigmoid
계층을 파이썬으로는 어떻게 구현할까요? [그림
5
-
22
]를 참고해 다음과 같이
구현할 수 있습니다(소스 코드는
common
/
layers
.
py
에 있습니다).
class Sigmoid
:
def
__
init
__(
self
):
self
.
out
=
None
def forward
(
self
,
x
):
out
=
1
/
(
1
+
np
.
exp
(-
x
))
self
.
out
=
out
return out
def backward
(
self
,
dout
):
dx
=
dout
*
(
1
.
0
-
self
.
out
)
*
self
.
out
return dx
이 구현에서는 순전파의 출력을 인스턴스 변수
out
에 보관했다가, 역전파 때 그 변수를 사용해
계산을 수행합니다.
5.6
Affine
/
Softmax
계층 구현하기
5.6.1
Affine
계층
신경망의 순전파에서는 가중치 신호의 총합을 계산하기 때문에 행렬의 내적 (넘파이에서는
np
.
dot
( ))을 사용했습니다 (“
3
.
3
다차원 배열의 계산” 참고 ). 예를 들어 파이썬으로 다음과
같이 구현한 것을 기억하시나요?
171
5
장
-
오차역전파법
>>>
X
=
np
.
random
.
rand
(
2
)
# 입력
>>>
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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.