Halstead complexity measures

Halstead complexity measures are software metrics indroduced by Maurice Howard Halstead in 1977. These metrics are computed statically, without program execution.

Calculation

First we need to compute the following numbers, given the program:
* $n1$ = the number of distinct operators
* $n2$ = the number of distinct operands
* $N1$ = the total number of operators
* $N2$ = the total number of operands

From these numbers, five measures can be calculated:
* Program length:$N\; =\; N1\; +\; N2\; ,$
* Program vocabulary: $n\; =\; n1\; +\; n2\; ,$
* Volume: $V=\; N\; imes\; log\_2\; n\; ,$
* Difficulty : $D=\; \{\; n\_1\; over\; 2\; \}\; imes\; \{\; N\_2\; over\; n\_2\; \}\; ,$
* Effort: $E=\; D\; *\; V\; ,$

The difficulty measure is related to the difficulty of the program to write or understand, e.g. when doing code review.

See also

* Function point
* Cyclomatic complexity

External links

* [http://www.sei.cmu.edu/str/descriptions/halstead.html Halstead complexity measures] by Edmond VanDoren, Kaman Sciences, Colorado Springs.