One of the key values here at Applepie is simplicity. As a member of Applepie I strive whenever possible to deliver lean, readable, manageable code that meets its requirements and is a pleasure for other developers to use. It’s not easy. To help ‘keep it simple’ we follow a number of practices, such as code peer reviews, which at there heart have the question: “Is this simple?”. The outcome of these practices leads to better code that we have qualified as manageable and elegant. Code we feel is simple.

However, Qualifying or feeling something to be simple is often not enough, we want hard fact, we want to quantify how well a body of code exhibits simplicity. One answer, is to analyse the code base and generate metrics that can support us in our quest to simplify. One of the best metric I’ve found for this is Cyclomatic Complexity.

Cyclomatic Complexity (CC) measures the complexity of your code by counting the number of paths through your code. The number of paths is the CC number. The bigger the CC number the more likely that code is difficult to conceptualize and also less likely you can unit test that code effectively. It’s a bit like navigating a road, a Y junction fine, a cross roads OK, a four-way interchange is (well for me anyway) reaching my cognitive limit.

As a rule of thumb, Cyclomatic Complexity Numbers are as follows:

• Simple - 11 or less is optimal
• Manageable - 11-21, may be problematic and will require large unit tests.
• Complex - 21-50 will be problematic and certainly will not be easy to test.
• Forget it - 50+ cannot be tested and requires self-actualized yogi chess grandmaster to understand.

So how to profile your code for CC. I’m going to focus on Java though similar tools exist for C#, PHP, Ruby, Python. The tool I’ve used for Java is PMD (works with the IDE of your choice). PMD generates many static metrics on your code base including Cyclomatic Complexity.

To install PMD follow the instructions on this PMD onJava article, or if you only have 5 minutes here’s a quick install guide for eclipse. Pop the exploded zip downloaded from PMD into your plugins folder. After you have installed the plugin you need to activate the metrics for your project. Go to the project properties and select the Metrics option and then select the enable metrics. That’s it! The metrics are then calculated and a metric view is presented.

McCabe Cyclomatic Complexity (CC) is the PMD metric we are interested in. PMD generates these CC statistics for the entire project. It allows you to drill down a tree of statistics and quickly ascertain the highest CC for each package, class and method. It even highlights items over a threshold in red (defaults to11, but is configurable). Now at last I have the CC count for every piece of code I work on.

These generated statistics gives a great overview of where code needs to be simplified and (hopefully) helps a bit more in answering “Is this simple?”, allowing me to back up my gut feel with some quantifiable statistics.

If you want to know more on Cyclomatic Complexity see here. If your interested in other metrics supporting simplicity see Operands on an operation.

This entry was posted on Wednesday, May 14th, 2008 at 9:28 and is filed under java, software engineering, useful tools. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.