December 2016
Intermediate to advanced
440 pages
9h 44m
Japanese
Content preview from アルゴリズムクイックリファレンス 第2版
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5.4
ブルームフィルタ
■
129
の値
w
が
B
に挿入されたことがないことを、
k
個のビット値の
1
つが
0
（この場合は
ビット
6
）ということから、迅速に示すことができる。しかし、値
x
については、値
は挿入されたことがないのに、その計算した
k
個すべてのビット値が
1
なので、偽
陽性を返す。
ビット
配列
B
図5-5 ブルームフィルタの例
5.4.1
入出力
ブルームフィルタ
は、
ハッシュに基づいた探索
のように値を処理する。まず、すべ
てが
0
に初期化された
m
ビットのビット配列から始める。値が挿入されるときに、
このビット配列の中の（異なる）ビット位置を計算する
k
個のハッシュ関数がある。
ブルームフィルタ
は、目標要素
t
がビット配列に挿入されたことがなく、したがっ
て、集まり
C
に存在しないことを示すことができると
false
を返す。また、目標要
素
t
がビット配列に挿入されたことがなくても偽陽性として
true
を返すことがある。
5.4.2
文脈
ブルームフィルタ
は、メモリ使用は効率的だが、偽陽性が受け入れられる場合だ
け役立つ。
ブルームフィルタ
を使って、失敗することが保証されているものを取り
除き、高価な探索の回数を減らすことができる。例えば、
ブルームフィルタ
を使って、
ディスクのストレージに高価な探索を行うかどう
か確かめることができる。
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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.