November 2019
Beginner to intermediate
408 pages
9h 29m
Korean
Content preview from 밑바닥부터 시작하는 비트코인
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12
장
블룸 필터
305
12.1.1
다중 해시함수 사용
전체 집합의 원소 개수가
1
백만 개라고 합시다. 한 그룹의 원소 개수가 여전히
5
개인 블룸 필
터를 만들고자 한다면 비트 필드의 길이는
1
,
000
,
000
/
5
=
200
,
000
비트여야 합니다. 각 그
룹은 평균
5
개의 원소로 이루어지고 관심 원소가
1
개라면 그룹에서 관심 원소의 비율은
20%
가 됩니다.
200
,
000
비트는
25
,
000
바이트이고 블룸 필터 설정값으로 전송하기에는 많은 데이
터양입니다. 더 좋은 방안이 없을까요?
해시함수를 여러 개 사용해서 블룸 필터를 구성하면 비트 필드의 길이를 상당히 줄일 수 있습
니다.
32
비트의 비트 필드에서
5
개의 해시함수를 사용하면
32
!/ (
27
!
5
!)~
200
,
000
개의 그룹
을 만들 수 있습니다.
3
1
백만 개의 원소 중에서 평균
5
개의 원소가 동일한
5
비트 조합을 갖게
됩니다. 이런 식으로
25K
바이트를 전송하는 대신
4
바이트 (
32
비트 )만 전송할 수 있습니다.
이를 구현하는 코드는 다음과 같습니다. 간단히 하기 위해 이전 예와 동일한
10
비트 필드를 사
용하지만 관심 원소는 두 가지로 가정했습니다.
>>> from helper import hash256, hash160
>>> bit_field_size = 10
>>> bit_field = [0] * bit_field_size ...
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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.