April 2020
Intermediate to advanced
816 pages
18h 32m
Chinese
Content preview from 精通機器學習
Become an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
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.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.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.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.
池化層
|
443
權總和
，
所以總共需要
2.25
億次浮點乘法
。
這種情況不像全連接層那麼糟糕
，
但仍然需要
大量的計算
。
此外
，
如果特徵圖是用
32-bit
浮點數來表示的
，
摺積層的輸出將佔用
200 ×
150 × 100 × 32 = 9,600
萬
bits（12 MB）
的
RAM
8
，
這只是一個實例而已
，
如果訓練批次有
100
個實例
，
這一層將使用
1.2 GB
的
RAM ！
在推理
（
也就是為新實例進行預測
）
期間
，
一個階層佔用的
RAM
可以在下一層計算結束
時釋出
，
所以只會使用兩個連續的階層所需的
RAM。
但是在訓練期間
，
在順向傳遞的過
程中算出來的東西都必須保留起來
，
讓逆向傳遞使用
，
所以你需要的
RAM（
至少
）
是所
有階層需要的
RAM
的總數
。
如果你的訓練因為記憶體不足而崩潰了
，
你可以試著降低小批次的大小
。
你也可以試著利用步幅來降低維數
，
或移除一些階層
，
或試著將
32-bit
浮
點數換成
16-bit
浮點數
，
或是將
CNN
分配給多台裝置
。
接下來我們要介紹
CNN
的第二種常見的元素
：
池化層
（pooling layer）。
池化層
知道摺積網路如何運作之後
，
池化層就很容易瞭解了
。
它們的目的是抽取輸入圖像的
子樣
本
（
也就是縮小它
）
來降低計算負擔
、
記憶體使用量
，
以及參數的數量
（
進而約束過擬的
風險
）。
如同摺積層
，
池化層裡面的各個神經元都被接到上一層有限數量的神經元的輸出
，
那些
神經元都位於一個小型的矩形感受區裡面
。
你必須和之前一樣定義它的大小
、
步幅
，
以及
填補類型
。
但是池化神經元沒有權重
，
它的工作只是使用
max（
最大值
）
或
mean（
平均
值
）
Become an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
and much more.
Read now
Unlock full access
More than 5,000 organizations count on O’Reilly
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.