What is Cyclomatic Complexity? Top Properties of Cyclomatic Complexity

LanguageNoteCOBOLGenerated lines of code and pre-processing instructions are not counted as lines of code. Writing code that simply duplicates functionality that your language’s standard library or your framework already provides is a sure way to increase complexity unnecessarily. Ifcode is a liability, you want to write only the strictly necessary amount of it. You’re likelier to introduce defects to an area of the codebase that you change a lot than to one you rarely touch. In addition, the more complex a given piece of code is, the more likely you are to misunderstand it and introduce a defect to it. A measure of the logical complexity of an algorithm, used in white-box testing.

Most languages provide similar constructs for “decision” points. By finding the code complexity the potential defect risk is also decreased which means the relative cost is reduced for finding the defects in source code. By the Cyclomatic complexity calculation, the program maintenance cost is also reduced. In general, in order to fully test a module, all execution paths through the module should be exercised. This implies a module with a high complexity number requires more testing effort than a module with a lower value since the higher complexity number indicates more pathways through the code.

You’ll learn how to reduce cyclomatic complexity and, more importantly, why you would want to do it. We recommend checking for cognitive complexity rather than cyclomatic complexity, and we pair that with a return statements check, as two of our 10 point maintainability inspection. Jill has in-depth knowledge of design, development, and quality processes. She is especially interested in coding standards and software metrics. At Perforce, she leads a world-wide group of high-capability technical consultants in delivering added-value products and services to customers. Jill holds a Masters degree in Computer Science from Brunel University and a BSc from University of Newcastle upon Tyne.

definition of cyclomatic complexity

Π – s + 2where π is the number of decision points in the program, and s is the number of exit points. This process is required because the highly coupled code is very difficult to modify. This means 5 test cases have to be made to implement this code for testing. Now, you may get a question that how it may get actually calculated.

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McCabe’s Cyclomatic complexity is another measure of cognitive complexity. This metric was developed by Thomas J. McCabe in 1976 and is recognized by many as a standard definition of cyclomatic complexity for measuring software complexity. Cyclomatic complexity may also be used for the evaluation of the semantic complexity of artificial intelligence programs.

The possible correlation between higher complexity measure with a lower level of cohesion is predicated on a module with more decision points generally implementing more than a single well defined function. A 2005 study showed stronger correlations between complexity metrics and an expert assessment of cohesion in the classes studied than the correlation between the expert’s assessment and metrics designed to calculate cohesion. In almost all cases, according to such a methodology, a module should have at least as many tests as its cyclomatic complexity; in most cases, this number of tests is adequate to exercise all the relevant paths of the function. Cyclomatic complexity is especially important when it comes to testing. By calculating the cyclomatic complexity of a function, for instance, you know the minimum number of test cases you’ll need to achieve fullbranch coverageof that function.

definition of cyclomatic complexity

In the following, even subgraphs will be identified with their edge sets, which is equivalent to only considering those even subgraphs which contain all vertices of the full graph. Number of unit tests that have failed with an unexpected exception. Depending on the language, a function is either a function or a method or a paragraph. Total count of Code Smell issues raised for the first time on New Code.

What You Should Do Next when You Find a High-Cyclomatic-Complexity Program?

The more complex the system, the more difficult it will be for changes to be made without disrupting other parts of the system. It is inversely proportional to code readability and easy to understand code. It means when the Cyclomatic complexity is greater the code is not easy to understand and difficult to read and when the complexity is less the code is easy to read and easy to understand. The recursive call is considered as one functional call otherwise it will create a loop situation that will create a problem to calculate the Cyclomatic complexity for source program. It can be used as a quality metric, gives relative complexity of various designs. “The role of empiricism in improving the reliability of future software”.

Suppose a program has a cyclomatic complexity of 5, meaning there are 5 different independent paths through the method. Cyclomatic complexity is one of the most valuable metrics in software engineering. It has important implications for code quality and maintainability, not to mention testing.


Preventive measures means any reasonable measures taken by any person after an incident has occurred to prevent or minimize pollution damage. Time Complexity where loop variable is incremented by 1, 2, 3, 4 .. It is used to measure the minimum effort and best areas of concentration for testing.

definition of cyclomatic complexity

Code complexity is typically measured using cyclomatic complexity, which is a metric from 1970s. Code complexity has been studied for many years and there are many definitions for it. The control flow graph of the source code above; the red circle is the entry point of the function, and the blue circle is the exit point.

Cyclomatic complexity definition

It is computed by using the control flow graph, where each node on the graph represents indivisible groups or commands within the program. It was developed by Thomas J. McCabe, Sr. in 1976 and is used to indicate the complexity of a program. It directly measures the number of linearly independent paths through a program’s source code. The concept, although not the method, is somewhat similar to that of general text complexity measured by the Flesch-Kincaid Readability Test.

It represents a minimum no. of tests required to execute every path in the code. Identical to Uncovered lines but restricted to new / updated source code. Number of conditions which are not covered by unit tests. Identical to Line coverage but restricted to new / updated source code. Identical to Condition coverage but restricted to new / updated source code.

  • It means when the Cyclomatic complexity is greater the code is not easy to understand and difficult to read and when the complexity is less the code is easy to read and easy to understand.
  • I have heard of a rule of thumb that you should strive to keep the CC below 5 to maintain good readability and maintainability of your code.
  • It directly measures the number of linearly independent paths through a program’s source code.
  • You can calculate it using the E-N+2P formula, but I would suggest you have this calculated automatically by a plugin.

Cyclomatic complexity measures the number of execution paths through code, but excessive return statements can make a function harder for a human to follow because control flow jumps around. The graph notation is used to find a number of ways for the given program and find the complexity of the program. The topological intricacy of the graph can be compared with computer program complexity.

Avoid Flag Arguments in Functions

For all the conditions of your Quality Gate, you know which condition is failing and which is not. Ratio between the cost to develop the code changed on New Code and the cost of the issues linked to it. Keep in mind that no metric is a panacea when used in isolation.

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As the program grew in this fashion, it would quickly reach the point where testing all of the paths was impractical. So, the cyclomatic complexity is a very important number. Hence, it always good to get a lesser number for cyclomatic complexity. Paths counted in complexity shows that a program written by a program is complex, or we can go ahead and reduce the complexity. This technique mostly used in basic testing of the white box.

That’s because code with high complexity is difficult to test. However, each branch of a “case” or “switch” statement tends to count as 1. In effect, this means CC hates case statements, and any code that requires them . Milestones means control points in the project that help to chart progress.

The cyclomatic complexity of a section of source code is the number of linearly independent paths within it. A measure of the number of linearly independent paths through a program module. Cyclomatic complexity is a measure for the complexity of code related to the number of ways there are to traverse a piece of code. This determines the minimum number of inputs you need to test all ways to execute the program.

Metric Definitions

This calculation is quite easy for a single function but when the number of function increases in the source program it increases the complexity calculation. The main reason for the increase in complexity is because of the function call which is not shown in the flow diagram. V is an expression used for defining the number of independent paths of the graph. It is the measure of the programs’s control complexity and not the data complexity. Is an upper bound for the number of test cases that are necessary to achieve a complete branch coverage. Will be equal to the number of programs in question, as each subprogram will appear as a disconnected subset of the graph.

Instead of using a switch case to go over many possibilities and decide which one the code will execute, you can leverage thestrategy pattern. Sure, at some point in the code, you’ll still need a switch case. After all,someonehas to decide which actual implementation to use. However, that point becomes the only point in the code that needs that decision structure.

Introduction to Cyclomatic Complexity

If the program does not have any loop, its complexity is lower. When the program encounters any loop, the complexity increases. Calculating the cyclomatic complexity of the program is very easy by the following formula.

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