jm + daniel-lemire   3

Daniel Lemire's latest cool hack -- a SIMD library to parse gigabytes of JSON document per second
fast  json  parsing  speed  simd  avx  c++  algorithms  hacks  daniel-lemire 
february 2019 by jm
A fast alternative to the modulo reduction
(x * N) div 2^32 is an equally fair map reduction, but faster on modern 64-bit CPUs
fairness  modulo  arithmetic  algorithms  fair-mapping  reduce  daniel-lemire 
june 2016 by jm
Roaring Bitmaps
Bitsets, also called bitmaps, are commonly used as fast data structures. Unfortunately, they can use too much memory. To compensate, we often use compressed bitmaps. Roaring bitmaps are compressed bitmaps which tend to outperform conventional compressed bitmaps such as WAH, EWAH or Concise. In some instances, they can be hundreds of times faster and they often offer significantly better compression.

Roaring bitmaps are used in Apache Lucene (as of version 5.0 using an independent implementation) and Apache Spark (as of version 1.2).
bitmaps  bitsets  sets  data-structures  bits  compression  lucene  spark  daniel-lemire  algorithms 
november 2014 by jm

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