Category Archives: Programming

Programming – C/C++, Java, Ksh, Python, ML

Why list and charlist are confusing in Elixir

This post talks about list and charlist in Elixir, and discusses one specific issue in Elixir. Let’s look at the confusing thing in Elixir: iex(2)> a = [7] ‘\a’ iex(3)> b = ‘\a’ ‘\a’ iex(4)> a == b true iex(5)> … Continue reading

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A PoC of DoS attack in Elixir Actor Model

The naive way of using the Actor model in Elixir is using “receive” in a loop, which is then “spawn”d as a Erlang process. Unfortunately, a potential DoS attack could happen if the pattern matching is not coded carefully with … Continue reading

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A pitfall of GenServer programming in Elixir

OTP as a programming platform/framework, empowers not only Erlang, but also Elixir. This post looks into a pitfall when programming GenServer in Elixir, and provides a potential solution. All callbacks in the GenServer behavior have a limited and pre-defined possible … Continue reading

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Pitfalls in negative indexing in C

Negative indexing in C, such as a[-1], is legit, although rarely used. There are reasons (pitfalls) why negative indexing is not recommended. This post discusses these pitfalls when using negative indexing (for fun). 1. Negative indexing within the bound In … Continue reading

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getdelays – get delay accounting information from the kernel

Top may be the most common tool in use whenever a preformance issue is hit. It is simple, quick and dumb. Besides the heavy metal stuffs like perf and gprof, another really useful and simple tool is getdelays, which provides … Continue reading

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Linux kernel I/O Stack Diagram

Found this figure online. The title of this diagram may be biased as it is not the complete I/O stack but a concentration on block devices with a focus on SCSI layer. Some important missing stuffs, in my opinion, include … Continue reading

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Python Levenshtein distance – Choose Python package wisely

Brad and I were working on some text similarity computation. One of the most popular string distance functions is the Levenshtein distance, which is also called the edit distance. We use Python for its brevity and widely-library support (OK, I … Continue reading

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