One of the more popular complexity measures is McCabe's Cyclomatic Complexity (CC). The theory behind CC is simple: CC is a measure of the number of control flows within a module. A module is defined as a set of executable code that has an entrance and an exit. Control flow helps determine the number of paths through the module. The greater the number of paths through the module, the greater is the module's complexity.
The cyclomatic number for a module is equivalent to the number of linearly independent paths through the module and can be used to determine the minimum number of distinct tests that must be executed to test every executable statement at least once.
CC measurements may be performed ..
1. by counting the nodes (correspond to the corners) and edges (correspond to the bodies of the arrows) of the module graph
CC = # of edges - # of nodes + 2
2. by counting the number of binary decision points.
CC = # of binary decisions + 1
After we calculate the CC number for a module, what do we do with it and what does the CC number mean ? Stated simply, a higher CC signifies greater complexity of the module and corresponds to greater difficulty to test and maintain the module. Rules have been put forth on interpreting CC numbers. One such rule indicates that a CC > 20 signifies a high degree of complexity and risk of code being prone to defects. There are also rules that try to predict the probability of introducing regressions or inserting defects while trying to fix another defect, using the CC number. Here too, the higher CC corresponds to a greater probability of introducing new / additional defects while trying to make fixes to other defects. CC is helpful in trying to gain an insight into the difficulty to maintain and test code.
The following are extensions of Cyclomatic Complexity.
The cyclomatic number for a module is equivalent to the number of linearly independent paths through the module and can be used to determine the minimum number of distinct tests that must be executed to test every executable statement at least once.
CC measurements may be performed ..
1. by counting the nodes (correspond to the corners) and edges (correspond to the bodies of the arrows) of the module graph
CC = # of edges - # of nodes + 2
2. by counting the number of binary decision points.
CC = # of binary decisions + 1
After we calculate the CC number for a module, what do we do with it and what does the CC number mean ? Stated simply, a higher CC signifies greater complexity of the module and corresponds to greater difficulty to test and maintain the module. Rules have been put forth on interpreting CC numbers. One such rule indicates that a CC > 20 signifies a high degree of complexity and risk of code being prone to defects. There are also rules that try to predict the probability of introducing regressions or inserting defects while trying to fix another defect, using the CC number. Here too, the higher CC corresponds to a greater probability of introducing new / additional defects while trying to make fixes to other defects. CC is helpful in trying to gain an insight into the difficulty to maintain and test code.
The following are extensions of Cyclomatic Complexity.
- CCD (Cyclomatic Complexity Density) is used to predict maintenance productivity and is derived by dividing CC by LOC (Lines of Code). Higher CCD corresponds to lower maintenance productivity.
- ECC (Essential Cyclomatic Complexity) measures the cyclomatic complexity after the structured constructs (such as if, while, case, sequence) are removed.
