I Do Not Know C

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“The purpose of this article is to make everyone (especially C programmers) say: “I do not know C”.

I want to show that the dark corners of C are much closer than it seems, and even trivial code lines may contain undefined behavior.

The article is organized as a set of questions and answers. All the examples are separate files of the source code…”

http://kukuruku.co/hub/programming/i-do-not-know-c

SmileMiner (Statistical Machine Intelligence and Learning Engine)

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“SmileMiner (Statistical Machine Intelligence and Learning Engine) is a pure Java library of various state-of-art machine learning algorithms. SmileMiner is self contained and requires only Java standard library.

SmileMiner is well documented and you can browse the javadoc for more information. A basic tutorial is avilable on the project wiki.

To see SmileMiner in action, please download the demo jar file and then run java -jar smile-demo.jar…”

https://github.com/haifengl/smile

Beginning deep learning with 500 lines of Julia

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“There are a number of deep learning packages out there. However most sacrifice readability for efficiency. This has two disadvantages: (1) It is difficult for a beginner student to understand what the code is doing, which is a shame because sometimes the code can be a lot simpler than the underlying math. (2) Every other day new ideas come out for optimization, regularization, etc. If the package used already has the trick implemented, great. But if not, it is difficult for a researcher to test the new idea using impenetrable code with a steep learning curve. So I started writing KUnet.jl which currently implements backprop with basic units like relu, standard loss functions like softmax, dropout for generalization, L1-L2 regularization, and optimization using SGD, momentum, ADAGRAD, Nesterov’s accelerated gradient etc. in less than 500 lines of Julia code. Its speed is competitive with the fastest GPU packages (here is a benchmark). For installation and usage information, please refer to the GitHub repo. The remainder of this post will present (a slightly cleaned up version of) the code as a beginner’s neural network tutorial (modeled after Honnibal’s excellent parsing example)…”

http://www.denizyuret.com/2015/02/beginning-deep-learning-with-500-lines.html

How TCP backlog works in Linux

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“When an application puts a socket into LISTEN state using the listen syscall, it needs to specify a backlog for that socket. The backlog is usually described as the limit for the queue of incoming connections.

Because of the 3-way handshake used by TCP, an incoming connection goes through an intermediate state SYN RECEIVED before it reaches the ESTABLISHED state and can be returned by the accept syscall to the application (see the TCP state diagram). This means that a TCP/IP stack has two options to implement the backlog queue for a socket in LISTEN state:

  1. The implementation uses a single queue, the size of which is determined by the backlog argument of the listen syscall. When a SYN packet is received, it sends back a SYN/ACK packet and adds the connection to the queue. When the corresponding ACK is received, the connection changes its state to ESTABLISHED and becomes eligible for handover to the application. This means that the queue can contain connections in two different state: SYN RECEIVED and ESTABLISHED. Only connections in the latter state can be returned to the application by the accept syscall.
  2. The implementation uses two queues, a SYN queue (or incomplete connection queue) and an accept queue (or complete connection queue). Connections in state SYN RECEIVED are added to the SYN queue and later moved to the accept queue when their state changes to ESTABLISHED, i.e. when the ACK packet in the 3-way handshake is received. As the name implies, the accept call is then implemented simply to consume connections from the accept queue. In this case, the backlog argument of the listen syscall determines the size of the accept queue…”

http://veithen.github.io/2014/01/01/how-tcp-backlog-works-in-linux.html

Python 3 RPMs are now available for RHEL/CentOS 6/7

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“Python 3 is a new version of the language that is incompatible with the 2.x
line of releases. The language is mostly the same, but many details, especially
how built-in objects like dictionaries and strings work, have changed
considerably, and a lot of deprecated features have finally been removed…”

http://dl.iuscommunity.org/pub/ius/testing/CentOS/6/x86_64/repoview/python34u.html

https://iuscommunity.org/pages/Repos.html#release-packages

Proving that Android’s, Java’s and Python’s sorting algorithm is broken (and showing how to fix it)

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“Tim Peters developed the Timsort hybrid sorting algorithm in 2002. It is a clever combination of ideas from merge sort and insertion sort, and designed to perform well on real world data. TimSort was first developed for Python, but later ported to Java (where it appears as java.util.Collections.sort and java.util.Arrays.sort) by Joshua Bloch (the designer of Java Collections who also pointed out that most binary search algorithms were broken). TimSort  is today used as the default sorting algorithm for Android SDK, Sun’s JDK and OpenJDK. Given the popularity of these platforms this means that the number of computers, cloud services and mobile phones that use TimSort for sorting is well into the billions…”

http://envisage-project.eu/proving-android-java-and-python-sorting-algorithm-is-broken-and-how-to-fix-it/

How to process input and output streams in Steel Bank Common Lisp?

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“I’m trying to figure out how to use the output stream of one program I start with RUN-PROGRAM so it can be used as the input of another program started with RUN-PROGRAM (i.e., the moral and perhaps literal equivalent of piping). I’ve tried using a number of combinations of the :INPUT, :OUTPUT and :WAIT keyword arguments, but nothing I’ve hit upon has been productive so far. Any tips would be helpful; for example, how would I go about doing something like ls | grep lisp from the shell?…”

http://stackoverflow.com/questions/2353353/how-to-process-input-and-output-streams-in-steel-bank-common-lisp

Trend analysis at the shallow end of the pool

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“I have always wondered why some people feel Perl has to suck for their choice of language to be valid. It looks like there are a bunch of people who just try to satisfy their need for approval by seeking what’s most popular, and trying to hitch their wagon to that train. I do not know what they can gain by this, but they exist.

Yesterday, I noticed a post on HN which linked to a Google trends comparison of Perl and Python:…”

http://www.nu42.com/2015/02/trend-analysis-shallow-end.html

16 Months of Functional Programming

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“I’d like to share my experience with functional programming in this article. I feel like I’ve learned more in the past 16 months about computer science and computer systems in general than I have in the past 10 years thanks to my foray into Scala and the world of functional programming. The reason functional programming forces you to learn so much is because it challenges every assumption about writing software that you had. Oftentimes you can’t believe that some common thing can be done in a different way and then—boom!—a functional programming concept introduces a better way to do it and blows you away. So, what happened 16 months ago? I quit my startup and was looking for interesting projects to work on. I happened to get a consulting gig at 2lemetry that later turned into a full-time obsession with functional programming, MQTT brokers, and distributed systems. One of the things that impacted me while working at 2lemetry was exposure to Scala. It felt like whatever ideas I had about writing programs were off and I had to relearn everything from scratch…”

http://www.vasinov.com/blog/16-months-of-functional-programming/

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