Engineering

  • Implicit property getter can be harmful

    Property as a programming language’s feature has been around for a while. I first got to use it while developing a multi-tenant cloud-based point of sale application on .NET platform. The idea is to avoid the verbosity of calling getter/setter methods by invoking them behind the scene whenever a field is accessed/assigned.

  • Basic FBThrift example

    Facebook re-opensourced their fork of Apache Thrift some 4 years ago. Yet there is relatively little documentation and independent comparison to see if there is any performance bonus to gain by moving from Apache Thrift to FBThrift. The two are no drop-in replacement, thus, replacing one with another requires effort. This post first looks at setting up and running FBThrift. Complete code example used in this post can be found here.

  • Floating point binary representation in javascript

    Inspired by this post which explains how computer stores floating point number, Here is a bit of javascript code that print out a float32 number in binary format. Firstly, the main idea is, floating point number is represented similar to scientific representation of numbers using E notation.

  • Derivative of loss function in softmax classification

    Though frameworks like Tensorflow, Pytorch has done the heavy lifting of implementing gradient descent, it helps to understand the nuts and bolts of how it works. After all, neural network is pretty much a series of derivative functions. In this blog post, let’s look at getting gradient of the lost function used in multi-class logistic regression.

  • Perspectives in designing ML cost function

    For many different machine learning problems, finding a solution involves these similar steps.

  • How dk.brics.automaton regex library works

    This brics regex library is by far the fastest when comparing with openJDK java.util.regex and com.google.re2j. Let looks at what lie under the hood. dk.brics.automaton is a Finite automata library with application in Regex. The idea is similar to google re2j, which is to construct a DFA from regex string and matching an input string means advancing from one state to another. (google re2j is surprisingly the slowest in my test case. Which is probably due to my particular regex input, or some bug with Java port. I have not examined it yet)

  • Misconceptions when scale applications

    Once in a while, engineering managers and software engineers would triumphantly tell me to use a particular piece of technology because it is scalable or good for concurrency. Unfortunately, scaling an application means trading off different factors affecting an app’s performance and no single technology comes as silver bullet to solve them all. Below are some of the misconceptions I often hear.

  • How regex is implemented

    Recently at work, I need to take a deeper look at how optimization is done by different regex libraries and how they combine regex patterns. This document is examining 2 regex implementations: java.util.regex of OpenJDK and re2 of Google.

  • How java load classes

    For a while, I have delegated the task of managing java run command to IDE. Eclipse, Netbean and IntelliJ and all seem to do a decent job of masking away complexity of supplying java with JVM parameters, classpath, debugging options… Compared to other languages, the java run command can get horrendously long, not very suitable for handcrafting. Recently, when working on some sort of command generating at work and playing around with java command line arguments, I encountered some minor gotchas.

  • Shortcomings of web technologies in building a robust desktop application.

    As computation power and data are shifting to the edge, web applications are more and more like installed desktop applications with (limited) file system access, threading, offline storages… Frameworks such as Electron, which allow browser-based application to be packaged as standalone app, are gaining popularity. However, with great power comes great responsibility. Javascript, html, css have always been used to build webpages, which is a stateless and forgiving environment. A broken webpage can be remedied by hitting refresh button. The web is not used to be fast, users’ expectation for it is lower than for an installed application.

  • Java byte literal for value greater than 0x80

    In porting a piece of code from C++ to Java, I encountered statement like this:

  • C++ '&' operator

    Some note on C++ references

  • Concurrency in Java context

    Concurrency is an unavoidable fact in web development if the page ever gets pass more than one user (which is pretty much any service out there). But concurrency also poses a problem to data consistency. This post is a back-to-the-basics summary of techniques I’m aware of.

  • Running Odoo 8 on Pypy

    Pypy has not reached the point of compatibility that one could simply switch the interpreter. Some libraries need to be replaced, or installed with latest development code. Still, one can get the Odoo web running with a few changes.

  • Tornado Non-blocking Smtp Client

    Recently, I was developing a tornado-based web application at work. The idea of using Tornado is to base the whole web application on Tornado’s single-threaded IOloop, which enables the application to handle higher load compared to using other multi-threaded model (given the same hardware). Since there is no additional thread spawned to handle concurrent requests, no memory overhead. And besides, that help avoids context-switching cost when the program control is passed between threads.

  • Fibonacci Tail Recursion

    (Documenting my progress with Haskell. little by little)