My own experience, based on recent investigation with a grad
student to compile more evidence for his claims regarding
complexity metrics (in this case Harrison's entropy-based measure
rather than McCabe) was that the closer we looked at the measure
itself, the more flawed it seemed to be - both on fundamental
theoretical grounds, and also on the evidence presented for its
empirical validity.

I think there is some significant work waiting to be done in this
area. However the purposes that these metrics get put to are also
questionable, so doing the work to construct a sufficiently
controlled and validated metric would quite possibly result in it
being abused further. Is your other list just having a flame war,
or do you think there is someone who would like to make a serious
investigation? If the latter, I'm sure that there are plenty of
PPIG folk who would encourage it, and provide methodological


> Over on the libresoft mailing list we're having a conversation about  
> interpretation of complexity metrics (e.g. McCabe cyclometic  
> complexity etc).  The studies that we know on this metric demonstrate  
> that the metric is useful to predict bugs, but I often hear the  
> further interpretation that complexity actually causes more bugs (or  
> inhibits their fixes) because the code is harder to understand.
> That interpretation seems to need stronger validation than the  
> correlational studies.  I thought this forum might know of some  
> studies that approach this.  For example has anyone tried to measure  
> the impact of (e.g.) higher cyclometric complexity on the speed of  
> fixing a bug in code?  I'm thinking of some comparison of effort to  
> fix the "same bug" with different coding styles (one with high  
> cyclometric complexity, one with lots of function calls, something  
> else)?
> An alternative explanation of the correlation might be that complexity  
> metrics measure the difficulty of work (ie difficulty of the work is  
> driving both the complexity and the bugs, at the same time).
> Thanks,
> James

Alan Blackwell
Reader in Interdisciplinary Design, University of Cambridge
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