Talk Nerdy To Me

Vincenty’s Formula is an iterative solution for calculating the distance and direction between two points along the surface of Earth. For clarity, I’ve stripped out portions of the code I’ve put up for discussion, but you can download the entire Java source code from here. If you prefer C#, please see the C# version of this discussion.

Several years ago, I stumbled on a great pastime called “geocaching.” It’s a worldwide treasure hunting game where participants use handheld GPS receivers to find hidden “caches” – small boxes filled with prizes, trinkets, and “travel bugs“. The caches are hidden by other participants who post nothing more than the latitude and longitude on a website like Geocaching.com. My children and I have had a blast. It’s a great way for a grown man to justify playing in the woods (and buying an expensive gadget!) under the pretense of “playing with the kids.” With over 420,000 caches in 222 countries on all continents (including Antarctica!) there are bound to be several near you.

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Roundoff problems have been the bane of programmers since computers started handling floating point numbers. Floating point numbers are represented by a finite number of bytes. This limits the precision of numbers that may be represented – you only get so many significant digits. More subtly, however, finite length floating point numbers limit which numbers may be represented accurately. Repeating decimals (which, in a sense, require an infinite number of significant digits) cannot be represented precisely. You may only store the nearest value representable by the computer. This is the origin of annoying roundoff problems found in floating point arithmetic.

The C# and Java 4-byte float data type provides 7 significant digits of precision, while the 8-byte double type provides 15. Using the higher precision double data type helps minimize the roundoff error, but it must still be addressed.

So, when I encountered the C# 12-byte decimal data type with its 28 significant digits, and Java’s arbitrary size BigDecimal data type, I figured these were simply ways of further minimizing the problem with a wider floating point type. Only after digging deeper did I realize that the implementation behind both of these data types is a stroke of genius.

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I have to admit, when I first heard about the open source project Crap4j, I thought it was a joke. It sounded like a sarcastic, tongue-in-check spoof on the masses of brittle legacy Java code accumulating daily in software development shops around the world.

It isn’t a joke.

The Crap4j Web site describes the Change Risk Analysis and Predictions software metric as “a mildly offensive metric name to help protect you from truly offensive code.” Well said. The levity of the name belies the seriousness of the problem. Java is no longer a new language. Greenfield development has made way for maintenance and incremental upgrades to massive legacy code bases for which the original development team is long gone.

We all know legacy Java code is often poorly documented, but dig a little deeper and you’ll discover something even worse: it’s poorly tested! Now, consider that legions of developers have added little tweaks and bug fixes along the way without giving consideration to meaningful refactoring. What else can you do but throw up your hands (or your lunch) and declare “This code is crap!”

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I’ve recently started experimenting with NHibernate – the C#/.NET version of the Hibernate O/R matpping tool that was originally developed for Java. The Java version is very powerful, and I’m a huge fan of it. The C#/.NET version is, for the most part, a straight port of the Java code base (and an ugly port, in some ways). Nevertheless, it appears to be just as robust as its predecessor.

Be warned, however, that the NHibernate DLLs require a high level of trust in the ASP.NET environment they’re deployed to. I spent an entire weekend beating my head against a wall trying to get a simple app up on my GoDaddy account. I suspect NHibernate probably wasn’t designed with a medium trust environment in mind. I was able to make a few tweaks to get the code running with fewer permissions requirements. However, the permissions required to enable dynamic proxies – a fundamental part of the NHibernate architecture – are non-negotiable.

I learned from GoDaddy tech support that their Deluxe Windows plan, a shared host environment, simply doesn’t allow those permissions. I’d need to upgrade to a dedicated server, and that’s just a little too pricey for an environment simply for experimentation. I was able to get NHibernate working without any hacks at Webhost4life, but I thought I’d share what I tried first at GoDaddy just to help you understand the permissions implications if you’re in a medium trust environment — and how you might need to address them on your own projects.

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Vincenty’s Formula is an iterative solution for calculating the distance and direction between two points along the surface of Earth. For clarity, I’ve stripped out portions of the code I’ve put up for discussion, but you can download the entire C# source code from here. If you prefer Java, please see the Java version of this discussion.

Several years ago, I stumbled on a great pastime called “geocaching.” It’s a worldwide treasure hunting game where participants use handheld GPS receivers to find hidden “caches” – small boxes filled with prizes, trinkets, and “travel bugs“. The caches are hidden by other participants who post nothing more than the latitude and longitude on a website like Geocaching.com. My children and I have had a blast. It’s a great way for a grown man to justify playing in the woods (and buying an expensive gadget!) under the pretense of “playing with the kids.” With over 420,000 caches in 222 countries on all continents (including Antarctica!) there are bound to be several near you.

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Here’s a nasty bug that crept into one of my team’s projects recently. When will equivalent C# objects fail to compare as equal? The answer is “when operator== doesn’t work as expected.”

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All you geniuses and rocket scientists out there probably already know this, but I just stumbled on it, and I think it’s kind of cool. Did you know you can customize the adding and removing of C# event handlers? I didn’t.

I’m going to end this post with the question “Yes, but what’s it good for?” You folks with the Ph. D. in C#, feel free to scroll to the bottom and post your answers. For my fellow mortals out there, let me recap what I’m talking about.

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Okay, so I blogged about how C# BindingList<T> serialization is broken and how to fix it. The problem centers around filling a BindingList subtype with items that implement INotifyPropertyChanged. This enables your list to fire ListChanged events indicating ItemChanged whenever a property of a list item changes. Unfortunately, serializing and deserializing the list causes the ItemChanged notification to stop firing unless you take steps to properly rebuild the list. This happens because C# event handlers aren’t serializable, and .NET fails to rewire the listeners.

A colleague of mine asked for a quick example to demonstrate the problem, so I whipped up this test case.

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