All:
I m following up on our meeting yesterday with some material on code metrics.
There are a couple of metric families that are commonly used. The first are simple line counts. It s common for tools to have several varieties such as raw lines, non-blank lines, lines with comments, etc. There are also a few metrics
that count syntactic constructs in various ways, such as nesting depth.
Then there is the McCabe family which contains the much misunderstood Cyclomatic Complexity and a few relatives that attempt to compensate for its shortcomings; e.g. Essential Complexity, and Module Design Complexity.
The Halstead metrics are an antiquated family that are based on counting tokens in various ways. They don t appear to be widely used any more.
There are a bunch of Object-oriented metrics that are often about the relationship between classes: coupling, cohesion, etc.
I mentioned metrics used in the embedded industry and how there s a need for this to be more standardized. A metrics collection that seems to be popular in automotive is the HIS/KGAS set
https://docplayer.net/6136232-His-source-code-metrics.html . Here s a blog I wrote a little while ago that picks on one particular metric used in that set:
https://blogs.grammatech.com/why-npath-is-a-terrible-code-metric .
As I said in the meeting, metrics have numeric values, but we should also allow for exceptional results. For example:
Computing the metric leads to a numeric error such as divide by zero The metric can t be computed because it s inapplicable for some reason The value can t be reasonably expressed (e.g., a path count metric can easily yield 30-40 digit decimal values) The value is infinity (which
kind of infinity probably doesn t matter
ð )
There s some overlap between these of course. I ve seen them all in real life.
-Paul
--
Paul Anderson, VP of Engineering, GrammaTech, Inc.
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