Links for 2013-06-21

  • Java Concurrent Counters By Numbers

    threadsafe counters in the JVM compared. AtomicLong, Doug Lea’s LongAdder, a ThreadLocal counter, and a field-on-the-Thread-object counter int (via Darach Ennis). Nitsan’s posts on concurrency are fantastic

    (tags: counters concurrency threads java jvm atomic)

  • Ultimate Tic-Tac-Toe

    Tic-Tac-Toe Inception. whoa

    (tags: games tic-tac-toe inception recursion boardgames via:fp)

  • hlld

    a high-performance C server which is used to expose HyperLogLog sets and operations over them to networked clients. It uses a simple ASCII protocol which is human readable, and similar to memcached. HyperLogLog’s are a relatively new sketching data structure. They are used to estimate cardinality, i.e. the unique number of items in a set. They are based on the observation that any bit in a “good” hash function is indepedenent of any other bit and that the probability of getting a string of N bits all set to the same value is 1/(2^N). There is a lot more in the math, but that is the basic intuition. What is even more incredible is that the storage required to do the counting is log(log(N)). So with a 6 bit register, we can count well into the trillions. For more information, its best to read the papers referenced at the end. TL;DR: HyperLogLogs enable you to have a set with about 1.6% variance, using 3280 bytes, and estimate sizes in the trillions.
    (via:cscotta)

    (tags: hyper-log-log hlld hll data-structures memcached daemons sketching estimation big-data cardinality algorithms via:cscotta)

  • SSL/TLS overhead

    ‘The TLS handshake has multiple variations, but let’s pick the most common one – anonymous client and authenticated server (the connections browsers use most of the time).’ Works out to 4 packets, in addition to the TCP handshake’s 3, and about 6.5k bytes on average.

    (tags: network tls ssl performance latency speed networking internet security packets tcp handshake)

  • McLibel leaflet was co-written by undercover police officer Bob Lambert | UK news | guardian.co.uk

    The true identity of one of the authors of the “McLibel leaflet” is Bob Lambert, a police officer who used the alias Bob Robinson in his five years infiltrating the London Greenpeace group. [...] McDonald’s famously sued green campaigners over the roughly typed leaflet, in a landmark three-year high court case, that was widely believed to have been a public relations disaster for the corporation. Ultimately the company won a libel battle in which it spent millions on lawyers. Lambert was deployed by the special demonstration squad (SDS) – a top-secret Metropolitan police unit that targeted political activists between 1968 until 2008, when it was disbanded. He co-wrote the defamatory six-page leaflet in 1986 – and his role in its production has been the subject of an internal Scotland Yard investigation for several months. At no stage during the civil legal proceedings brought by McDonald’s in the 1990s was it disclosed that a police infiltrator helped author the leaflet.

    (tags: infiltration police mcdonalds libel greenpeace bob-lambert undercover 1980s uk-politics)

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