May 31, 2017 Volume 15, issue 2 PDF Data Sketching The approximate approach is often faster and more efficient. Graham Cormode Do you ever feel overwhelmed by an unending stream of information? It can seem like a barrage of new email and text messages demands constant attention, and there are also phone calls to pick up, articles to read, and knocks on the door to answer. Putting these pieces toge
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本日,PFI セミナーにて「乱択データ構造の最新事情 −MinHash と HyperLogLog の最近の進歩−」というタイトルで話をさせてもらいました.スライドは以下になります. Ustream の録画もあります. http://www.ustream.tv/recorded/48151077 内容としては,以下の操作を効率的に行うための集合に関するデータ構造 (Sketch) の最近の進歩を紹介しました. 集合の類似度の推定 (Jaccard 係数) 集合異なり数の推定 (distinct counting) どちらも重要かつ基礎的な操作で,b-bit MinHash や HyperLogLog など,既に実用的な手法が提案されており,実際にも使われています.しかし,2014 年になって,Odd Sketch や HIP Estimator という,これらをさらに改善する手法が立て続
はじめに 「さぁ、お前の罪の異なり数を数えろ!」と言われたときに使えそうな「HyperLogLog」という異なり数をカウントする方法を教えてもらったので、遊んでみた。 いつもながら論文ちゃんと読んでないので、条件やコード間違ってるかも。。。 HyperLogLogとは cardinalityと呼ばれる、要素の異なり数を決定する問題 かなり省メモリで精度のよい異なり数を推定できる方法 要素をそのまま保存せず、ハッシュ値に変換したものをうまくレジスタに保存しておく ので、レジスタサイズ程度しかメモリを使わない 並列化もできて、最近のbigdataとかで注目されている また、googleが並列計算用に改善したHyperLogLogを提案してるみたい http://blog.aggregateknowledge.com/2013/01/24/hyperloglog-googles-take-on-
We’ll look briefly in how you would utilize awesomeness of both Cascalog and HyperLogLog in order to execute Hadoop M/R tasks with amounts of data too big to have them in their original form. Intro HyperLogLog Cardinality estimator allowing you to count amount of distinct values. Cascalog The main use cases for Cascalog are processing "Big Data" on top of Hadoop or doing analysis on your local com
Statistical analysis and mining of huge multi-terabyte data sets is a common task nowadays, especially in the areas like web analytics and Internet advertising. Analysis of such large data sets often requires powerful distributed data stores like Hadoop and heavy data processing with techniques like MapReduce. This approach often leads to heavyweight high-latency analytical processes and poor appl
Matt Abrams recently pointed me to Google’s excellent paper “HyperLogLog in Practice: Algorithmic Engineering of a State of The Art Cardinality Estimation Algorithm” [UPDATE: changed the link to the paper version without typos] and I thought I’d share my take on it and explain a few points that I had trouble getting through the first time. The paper offers a few interesting improvements that are w
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