Discussing Cyclomatic Complexity

Such tools often depend on the language because they must parse the program and build its control flow. The highest complexity I have seen on a single method was 560. It was about 2000 lines of if statements in one method. Basically unmaintainable, untestable, full of potential bugs. Imagine all the unit test cases needed for that branching logic! The CASE statement may have to be redesigned using a factory pattern to get rid of the branching logic.

definition of cyclomatic complexity

The metric has a linear grow with the function complexity. Else …’ statement somewhere in a function increments the metric by one. It does not matter if the selection statement is nested or at the beginning of the function and it does not grow exponentially. E is the number of edges of the graph, N is the number of nodes and M is McCabe’s complexity. In this article we’ll take a fresh look at code complexity to define the Bumpy Road code smell. Along the way, you will see that absolute complexity numbers are of little interest; it’s much more interesting how that complexity is distributed and in what shape it manifests itself.

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Identifying nested logic is a valuable starting point, but we need to do better. Let’s see how by introducing the Bumpy Road code smell. Let’s start by discussing the limits of today’s metrics. There are other contributors to software complexity, one being the size of your code and, more particularly, the length of a function. A variation of the Cyclomatic Complexity Number that also captures those paths is the so called CCN2.

definition of cyclomatic complexity

As the Cyclomatic complexity calculates the independent paths for the source program, it gives the idea of a number of test cases for testing the source code. So when the number of independent path count is present it helps to test the code in that number of times. And by this, the whole code is covered for testing and solve the bugs if present. For example, if source code contains no control flow statement then its cyclomatic complexity will be 1 and source code contains a single path in it. Similarly, if the source code contains one if condition then cyclomatic complexity will be 2 because there will be two paths one for true and the other for false.

However, a comprehensive code complexity tool, such as Codacy, does. By knowing how many independent paths there are through a piece of code, we know how many paths there are to test. It is fair to say that the greater the number of nested conditions and the higher the level of complexity within those conditions, the higher the complexity of the code. Even junior developers know that most of the “complexity” of a code snippet is not relative to its number of if / else. Each line of the code may be difficult to understand, independently of its inclusion in a given path.

The following steps should be followed for computing Cyclomatic complexity and test cases design. Independent path is defined as a path that has at least one edge which has not been traversed before in any other paths. Determining the independent path executions thus proven to be very helpful for Developers and Testers. For example, consider a program that consists of two sequential if-then-else statements. The set of all even subgraphs of a graph is closed under symmetric difference, and may thus be viewed as a vector space over GF; this vector space is called the cycle space of the graph. The cyclomatic number of the graph is defined as the dimension of this space.

How to reduce cyclomatic complexity in 5 practical ways

This corresponds to the characterization of cyclomatic complexity as «number of loops plus number of components». Note that because each exit point loops back to the entry point, there is at least one such cycle for each exit point. A complexity value between 5-7 is moderate and still easy to understand.

definition of cyclomatic complexity

It’s no secret code is a complicated thing to write, debug, and maintain which is necessary for high software quality. Moreover, high code complexity brings with it a higher level of code defects, making the code costlier to maintain. The Bumpy Road code smell is a function that contains multiple chunks of nested conditional logic. Just like a bumpy road slows down your driving, a bumpy road in code presents an obstacle to comprehension. Worse, in imperative languages there’s also an increased risk for feature entanglement, which tends to lead to complex state management.

A number of 17,754 indicates project level complexity , which doesn’t have that much meaning. Finally, if you want a comprehensive tool for assessing code quality, and one that helps your developers learn and grow, then try out Codacy. So it makes sense that, if we understand the complexity of our code, and which sections are more complicated https://globalcloudteam.com/ than others, then we are in a far better position to reduce said complexity. 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 . The decision points may be your conditional statements like if, if … else, switch , for loop, while loop etc.

Since GF has two elements and the cycle space is necessarily finite, the cyclomatic number is also equal to the 2-logarithm of the number of elements in the cycle space. Non-significant comment lines (empty comment lines, comment lines containing only special characters, etc.) do not increase definition of cyclomatic complexity the number of comment lines. Software Engineering Stack Exchange is a question and answer site for professionals, academics, and students working within the systems development life cycle. I am a little confused on “Example Three”, as there is 5 cases and a default case in the code.

The complexity of a computer program can be correlated with the topological complexity of a graph. 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.

McCabe’s Cyclomatic Complexity with Flow Graph (Example)

The new identity revolves around our vision to “give code an intelligent voice” and reflects our forward-looking culture. The new logo reinforces the idea of artificial intelligence and CodeScene being there as an extra team member, guiding you toward better software and teams. If the value of V is equal to 1 then there is only one path in the graph which means there is only one solution to the computer program. The nodes are internally connected to each other when the next instruction is related to previous instruction.

definition of cyclomatic complexity

If the code is reformatted it does not affect the Cyclomatic complexity. Measurement is nothing but quantitative indication of size / dimension / capacity of an attribute of a product / process. Software metric is defined as a quantitative measure of an attribute a software system possesses with respect to Cost, Quality, Size and Schedule. In this, nested conditional structures are harder to understand than non-nested structures. Here «structured» means in particular «with a single exit per function».

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Of or relating to a software metric that measures the complexity of a program based on the number of linearly independent paths through the source code. Cyclomatic complexity is a software metric used to measure the complexity of a program. Thomas J. McCabe developed this metric in 1976.McCabe interprets a computer program as a set of a strongly connected directed graph. Nodes represent parts of the source code having no branches and arcs represent possible control flow transfers during program execution. The notion of program graph has been used for this measure, and it is used to measure and control the number of paths through a program.

  • Flow Graph notation for a program defines several nodes connected through the edges.
  • As a rule of thumb, you can use 4 as a good cyclomatic complexity, but between 5 and 7 should be acceptable if it makes the code more readable.
  • Along the way, you will see that absolute complexity numbers are of little interest; it’s much more interesting how that complexity is distributed and in what shape it manifests itself.
  • A good starting point might be the Wikipedia article on cyclomatic complexity.
  • One of the reasons for using metrics like cyclomatic complexity is that in general a human being can only keep track of about 7 pieces of information simultaneously in your brain.
  • The most accepted method to quantify software complexity is the Cyclomatic Complexity.

To reduce software complexity, developers must write small units of code but also avoid statements that make the code harder to understand and increase its complexity. There are multiple tools available to calculate software complexity. A simple tool is Codiga which flags functions with high cyclomatic complexity. Codiga requires no setup and provides complexity metrics for more than 15 languages. It’s the number of connected nodes in the control flow graph. The more you add nodes and connect them, the higher the complexity.


It is completely independent of source lines count in the computer program. The complexity does not depend on how many lines of code are there or how many branches are present in the graph. 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. The exit has been connected to the entry to make the graph strongly connected.

Binary decisions — such as “if” and “while” statements — add 1 to complexity. It is the measure of the programs’s control complexity and not the data complexity. Unfortunately, it is not always practical to test all possible paths through a program. Considering the example above, each time an additional if-then-else statement is added, the number of possible paths grows by a factor of 2. As the program grows in this fashion, it quickly reaches the point where testing all of the paths becomes impractical.

Tools for Cyclomatic Complexity calculation:

An application with few lines of code and a high number of conditionals nested within loops could have an extremely high cyclomatic complexity. On the other hand, an application with few conditions might have a low cyclomatic complexity. That’s oversimplifying it a big, but I think it gets the idea across.

Sometimes you can refactor and in some cases only a redesign will reduce the complexity. Without knowing more about what your application does, it might be normal to have a higher cyclomatic complexity. I would suggest measuring cyclomatic complexity on a class or method level, however, instead of just an application level. This is a little more managable, conceptually, I think – it’s easier to visualize or conceptualize the paths through a method than paths through a large application. Having a high total cyclomatic complexity on a program just means that a lot of logic has been implemented in the program but you cannot deduce any quality information from there.

The metric is completely independent of the code style. This is a big difference to the common line of code metric. We are proud to share this new identity with our community and hope that it will inspire all of us to write better code, build happier teams and future proof our software.

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