January 2017
Beginner to intermediate
312 pages
7h 3m
Korean
Content preview from 밑바닥부터 시작하는 딥러닝
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115
4
장
-
신경망 학습
def cross
_
entropy
_
error
(
y
,
t
):
delta
=
1e
-
7
return
-
np
.
sum
(
t
*
np
.
log
(
y
+
delta
))
여기에서
y
와
t
는 넘파이 배열입니다. 그런데 코드 마지막을 보면
np
.
log
를 계산할 때 아주
작은 값인
delta
를 더하고 있습니다. 이는
no
.
log
( ) 함수에
0
을 입력하면 마이너스 무한대
를 뜻하는 -
inf
가 되어 더 이상 계산을 진행할 수 없게 되기 때문입니다. 아주 작은 값을 더해
서 절대
0
이 되지 않도록, 즉 마이너스 무한대가 발생하지 않도록 한 것이죠. 그러면 이
cross
_
entropy
_
error
(
y
,
t
) 함수를 써서 간단한 계산을 해봅시다. 정답은 똑같이 ‘
2
’입니다.
>>>
t
=
[
0
,
0
,
1
,
0
,
0
,
0
,
0
,
0
,
0
,
0
]
>>>
y
=
[
0
.
1
,
0
.
05
,
0
.
6
,
0
.
0
,
0
.
05
,
0
.
1
,
0
.
0
,
0
.
1
,
0
.
0
,
0
.
0
]
>>>
cross
_
entropy
_
error
(
np
.
array
(
y
),
np
.
array
(
t
))
0
.
51082545709933802
>>>
>>>
y
=
[
0
.
1
,
0
.
05
,
0
.
1
,
0
.
0
,
0
.
05
,
0
.
1
,
0
.
0
,
0
.
6
,
0
.
0
,
0
.
0
]
>>>
cross
_
entropy
_
error
(
np
.
array
(
y
),
np
.
array
(
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.