Category Archives: Programming

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

Python Levenshtein distance – Choose Python package wisely

Posted on May 2, 2015 by daveti

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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Retrieve PID from the packet in Unix domain socket – a complete use case for recvmsg()/sendmsg()

Posted on February 17, 2015 by daveti

The original question was how to retrieve the PID of the packet (sender) in the Unix domain socket. As titled, the answer is recvmsg()/sendmsg(). However, the most useful information I could find online is Michael’s man7.org. People keep talking about … Continue reading →

Posted in OS, Programming | Tagged , , , , , , | 1 Comment

Bash Hacking – bash2, add setting CPU affinity support to the Bash

Posted on January 29, 2015 by daveti

This post is NOT initially designed for how to hack Bash. But it does tell the truth that hacking Bash is not that hard, by adding a useful feature to Bash itself – setting CPU affinity support. Have fun and … Continue reading →

Posted in OS, Programming | Tagged , , , , , , | 4 Comments

Python Internals – Integer object pool (PyIntObject)

Posted on December 11, 2014 by daveti

Starting from this post, I will try to make a series of blogs on Python Internals, where Python object mechanism, Python bytecode (pyc) and Python VM are gonna be discussed. We will also talk about the limited resource online about … Continue reading →

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Python Hacking – urlopen timeout issue

Posted on November 14, 2014 by daveti

Recent playing with Python urllib2 reveals an interesting fact that the timeout parameter of urlopen() does not work sometimes. The interesting issue has successfully pushed me deep into the Python source code for debugging. The final debugging, without surprise, shows … Continue reading →

Posted in Programming, Stuff about Compiler | Tagged , , , , , , | 5 Comments

Hack Go – generate non-FIPS DSA key parameters using hacked Go compiler

Posted on October 15, 2014 by daveti

Common DSA key parameter generation follow FIPS 186-3, which requires (L, N) bits length for P and Q, where L is at least 1024 and N is at least 160. However, sometimes we may want non-FIPS (L, N), for example, … Continue reading →

Posted in Programming, Security | Tagged , , , | 1 Comment

byte order – Linux kernel byte order APIs

Posted on August 23, 2014 by daveti

Most of the time, user-space applications do not care about the endian of the running machine, like we call send() and recv() directly expecting the right order of the data and they work! However, things could be changed if you … Continue reading →

Posted in OS, Programming | Tagged , , | 2 Comments

ksig – sending signals from the kernel space to the user space

Posted on August 23, 2014 by daveti

While syscall kill() gives users the ability to send certain signal to certain process in the user space of Linux, the story is totally different if we want to send signals from the kernel space to the user space. After … Continue reading →

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Book Recommendation – Building Probabilistic Graphical Models with Python

Posted on August 9, 2014 by daveti

“Building Probabilistic Graphical Models with Python” is the 3rd book I have reviewed from PACKT publishing. It has just been released on this June. Compared to the classic book of PGM – “PGM: Principles and Techniques” by Dr. Koller, this … Continue reading →

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Python hacking – make ElementTree support line number

Posted on July 4, 2014 by daveti

An easy way to parse XML in Python is using Python xml.etree.ElementTree, which parses the XML document/data into a tree structure, where each node is an Element object. Only within few lines of code, one can extract all the XML … Continue reading →

Posted in Programming | Tagged , , , , | 16 Comments