蓄水池抽样算法 (Reservoir Sampling Algorithm) 蓄水池抽样算法简介 蓄水池抽样算法是随机算法的一种,用来从N个样本中随机选择K个样本,其中N非常大(以至于N个样本不能同时放入内存)或者N是一个未知数。其时间复杂度为O(N),包含下列步骤 (假设有一维数组 S, 长度未知,需要从中随机选择 k 个元素, 数组下标从 1...
蓄水池抽样算法(Reservoir Sampling Algorithm)解决了未知长度数据的均匀抽样问题,即:给定一个数据流,数据流长度 很大,且 直到处理完所有数据之前都不可知,请问如何在只遍历一遍数据的情况下,能够随机选取出 个不重复的数据,且每个数据被取到的概率都为 ? 这个问题有3个主要难点: 数据流长度 很大且不可知,不能一次...
1#include <iostream>2#include <string>3#include <vector>4#include <cassert>5#include <cstdio>6#include <cstdlib>7#include <ctime>8usingnamespacestd;910/**11* Reservoir Sampling Algorithm12*13* Description: Randomly choose k elements from n elements ( n usually is large14* enough so that...
Reservoir sampling algorithm can be used for randomly choosing a sample from a stream of n items, where n is unknow. Here we still need to prove that Consider the (i)th item, with its compatibility probability of 1/i. The probability I will be choose the i at the time n > i can ...
Reservoir Sampling,水塘抽样算法是随机算法的一种,通常用于选取简单随机样本。 Reservoir Sampling 的用途 对于一个固定样本,样本总数为n,要在其中随机抽取k个样本,我们可以通过在[0,n)中进行随机取数,以保证选取样本的随机性。但是,当n变成一个极大的不固定的数,大到无法将n个样本全部载入到内存中,那么上述通过[...
Reservoir Sampling 蓄水池采样算法 sampling遍历数据数组算法 问题描述:给定一串很长的数据流,对该数据流中数据只能访问一次,使得数据流中所有数据被选中的概率相等。 为为为什么 2023/07/20 4710 蓄水池抽样-Reservoir Sampling 编程算法 英文原文:hadoop-stratified-randosampling-algorithm 译者:bruce-accumulate 引言:众...
It is very simple to distribute the reservoir sampling algorithm to n nodes. Split the data stream into n partitions, one for each node. Apply reservoir sampling with reservoir size s, the final reservoir size, on each of the partitions. Finally, aggregate each reservoir into a final reservoir...
It’s called reservoir sampling because the selected items are placed into a reservoir (i.e. a holding set). As each stream-tuple is received, the algorithm updates dynamically. The reservoir can be updated with replacement, or without replacement. Originally developed for one-pass processing ...
One can define a generator which abstractly represents a data stream (perhaps querying the entries from files distributed across many different disks), and this logic is hidden from the reservoir sampling algorithm. Indeed, this algorithm works for any iterable, although if we knew the size of ...
蓄水池抽样算法(Reservoir sampling)具体实现: Algorithm R: 由Alan Waterman1最初提出的一种简单但慢的实现方式。算法伪代码图如下所示: 证明Algorithm R每个样本被取到概率相同: 可以用数学归纳的方法来证明。 数学归纳法原理: 例如:你有一列很长的直立着的多米诺骨牌,如果你可以: 证明第一张骨牌会倒。 假设只...