Log Structured Merge Trees - ben stopford
It’s nearly a decade since Google released its ‘Big Table’ paper. One of the many cool aspects of that paper was the file organisation it uses. The approach is more generally known as the Log Structured Merge Tree, after this 1996 paper, although the algorithm described there differs quite significantly from most real-world implementations. LSM is now used in a number of products as the main file
A Fast, Minimal Memory, Consistent Hash Algorithm
We present jump consistent hash, a fast, minimal memory, consistent hash algorithm that can be expressed in about 5 lines of code. In comparison to the algorithm of Karger et al., jump consistent hash requires no storage, is faster, and does a better job of evenly dividing the key space among the buckets and of evenly dividing the workload when the number of buckets changes. Its main limitation is
Mutable Algorithms in Immutable Languages, Part 1 · tel.github.io
One of the big challenges you might face when learning a language like Haskell which favors immutability or purity is that suddenly all of the algorithms you once kept at your side have… well, by-and-large they’ve vanished. Many “imperative” algorithms rely upon mutable memory to work and it can be a challenge to remove that dependency. Usually in the process you’ll learn quite a bit about purely
Visualizing Algorithms
The power of the unaided mind is highly overrated… The real powers come from devising external aids that enhance cognitive abilities. —Donald Norman Algorithms are a fascinating use case for visualization. To visualize an algorithm, we don’t merely fit data to a chart; there is no primary dataset. Instead there are logical rules that describe behavior. This may be why algorithm visualizations are
Examples of Hash Functions for Hash Table Lookup
Now that we have some tools for evaluating hash functions for table lookup, let's look at several common hashes. I usually define "ub4" as unsigned long int; it's supposed to be an unsigned 4-byte integer type. The additive hash, seen in commercial code: ub4 additive( char *key, size_t len, ub4 prime) { ub4 hash; size_t i; for (hash=(ub4)len, i=0; i<len; ++i) hash = hash+key[i]; return (hash % pri
What is the optimal algorithm for the game 2048?
I have recently stumbled upon the game 2048. You merge similar tiles by moving them in any of the four directions to make "bigger" tiles. After each move, a new tile appears at random empty position with a value of either 2 or 4. The game terminates when all the boxes are filled and there are no moves that can merge tiles, or you create a tile with a value of 2048. One, I need to follow a well-def
Gen I Capture Mechanics
Special thanks to a_magical_me, who started analyzing the algorithm, let me use his notes and then provided me with an assembly dump to pick up where he left off. The hacking genius is mostly his. If you were an avid player of Red, Blue and Yellow, you may have read the other capture mechanics sections and fleetingly wondered, "But what about the times in R/B/Y when it would say, 'The ball missed
Reddit’s empire is founded on a flawed algorithm - Ian's Tech Notes
Posted on December 9, 2013 Reddit has a bug in their code. This bug is currently present in their production platform, and has been for years. It affects one of the most important algorithms in the entire site, the “Hot” ranking algorithm for link popularity. It has real, demonstrable negative effects. It has been reported to Reddit’s technical team several times and never fixed. The Bug Reddit ne
Which hashing algorithm is best for uniqueness and speed? - Software Engineering Stack Exchange
Which hashing algorithm is best for uniqueness and speed? Example (good) uses include hash dictionaries. I know there are things like SHA-256 and such, but these algorithms are designed to be secure, which usually means they are slower than algorithms that are less unique. I want a hash algorithm designed to be fast, yet remain fairly unique to avoid collisions.
MARISA: Matching Algorithm with Recursively Implemented StorAge
Abstract: Matching Algorithm with Recursively Implemented StorAge (MARISA) は Trie をコンパクトに表現する程度の能力を持つデータ構造です．libmarisa は MARISA を C++ で実装したライブラリであり，MARISA による辞書を構築したり，辞書からの検索をおこなったりできます．libmarisa の基本的な機能に対応するコマンドラインツールを用意しているので，辞書のサイズがどのくらいになるのか，検索にどのくらい時間がかかるのか，などを手軽に試すことができます． 概要 Matching Algorithm with Recursively Implemented StorAge (MARISA) は Trie に対するコンパクトなデータ構造であり，動的な更新には対応していないものの，高い空間効率と
LOUDSトライのライブラリの性能を比較してみた - EchizenBlog-Zwei
LOUDSは木構造を非常に小さなデータサイズで表現することができる簡潔データ構造の一種。とくに自然言語処理ではトライ木という木構造が重要で形態素解析や日本語入力(IME)など多くの場面で利用されている。 トライ木としてはdouble arrayが有名。LOUDSはdouble arrayより速度で劣る反面、データサイズを非常に小さく抑えることが可能である。このため近年、大規模データを扱うためのデータ構造として注目されている。 LOUDSを用いたトライ木には優れた実装がいくつかある。なかでも有名なものとして@s5yata氏によるmarisa-trieと@hillbig氏によるux-trieがある(ux-trieのクローンであるrx-trieはGoogleIMEで利用されている)。 今回はこれらのライブラリと、参考までに私の作ったerika-trieを使ってみて簡単に性能比較をしてみた。 評価
Natural Order String Comparison
by Martin Pool This project has moved to github.com/sourcefrog/natsort. Computer string sorting algorithms generally don't order strings containing numbers in the same way that a human would do. Consider: rfc1.txt rfc2086.txt rfc822.txt It would be more friendly if the program listed the files as rfc1.txt rfc822.txt rfc2086.txt Filenames sort properly if people insert leading zeros, but they don't
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TinyPNG: Lossy compression for PNG that preserves full transparency. | Hacker News
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Wilson’s Algorithm
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clojure-contrib/lazy_seqs.clj at 78ee9b3e64c5ac6082fb223fc79292175e8e4f0c · richhickey/clojure-contrib