Complexity of reference (Elshof)

Title short form	Elshof
Categories	Efficiency, maintainability, reusability
Definition	Complexity of the data flow of a POU The complexity of reference is calculated using the following formula: <Number of variables used> / <Number of variable accesses>
Further information	Only variable accesses in the implementation part of the POU are taken into account.

Sample:

PROGRAM MAIN
VAR
    i, j  : INT;
    k     : INT := GVL.m;
    b, c  : BOOL;
    fb    : FB_Sample;
END_VAR

fb(paramA := b);   // +3 accesses (fb, paramA and b)
i := j;            // +2 accesses (i and j)
j := GVL.d;        // +2 accesses (j and GVL.d)

For the metric Complexity of reference (Elshof), MAIN:

Number of variables used = 6
Number of variable accesses = 7
Complexity of reference (Elshof) = number of variables used/number of variable accesses = 6/7 = 0.85

Attention:

c and k are not used and therefore do not count as "variables used".
The assignment k : INT := GVL.m; is not counted as it is part of the declaration of the program.