{"id":123,"date":"2021-12-22T14:44:08","date_gmt":"2021-12-22T14:44:08","guid":{"rendered":"http:\/\/127.0.0.1\/wordpress\/?p=123"},"modified":"2021-12-31T10:53:31","modified_gmt":"2021-12-31T10:53:31","slug":"complexity-as-a-software-metric","status":"publish","type":"post","link":"http:\/\/127.0.0.1\/wordpress\/complexity-as-a-software-metric\/","title":{"rendered":"Complexity as a software metric"},"content":{"rendered":"\t\t<div data-elementor-type=\"wp-post\" data-elementor-id=\"123\" class=\"elementor elementor-123\" data-elementor-settings=\"[]\">\n\t\t\t\t\t\t\t<div class=\"elementor-section-wrap\">\n\t\t\t\t\t\t\t<section class=\"elementor-section elementor-top-section elementor-element elementor-element-55acff8 elementor-section-boxed elementor-section-height-default elementor-section-height-default\" data-id=\"55acff8\" data-element_type=\"section\">\n\t\t\t\t\t\t<div class=\"elementor-container elementor-column-gap-default\">\n\t\t\t\t\t<div class=\"elementor-column elementor-col-100 elementor-top-column elementor-element elementor-element-30e73067\" data-id=\"30e73067\" data-element_type=\"column\">\n\t\t\t<div class=\"elementor-widget-wrap elementor-element-populated\">\n\t\t\t\t\t\t\t\t<div class=\"elementor-element elementor-element-8880394 elementor-widget elementor-widget-heading\" data-id=\"8880394\" data-element_type=\"widget\" data-widget_type=\"heading.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t<style>\/*! elementor - v3.5.0 - 12-12-2021 *\/\n.elementor-heading-title{padding:0;margin:0;line-height:1}.elementor-widget-heading .elementor-heading-title[class*=elementor-size-]>a{color:inherit;font-size:inherit;line-height:inherit}.elementor-widget-heading .elementor-heading-title.elementor-size-small{font-size:15px}.elementor-widget-heading .elementor-heading-title.elementor-size-medium{font-size:19px}.elementor-widget-heading .elementor-heading-title.elementor-size-large{font-size:29px}.elementor-widget-heading .elementor-heading-title.elementor-size-xl{font-size:39px}.elementor-widget-heading .elementor-heading-title.elementor-size-xxl{font-size:59px}<\/style><h1 class=\"elementor-heading-title elementor-size-default\">Complexity as a software metric<\/h1>\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-e3cc9bf elementor-widget elementor-widget-image\" data-id=\"e3cc9bf\" data-element_type=\"widget\" data-widget_type=\"image.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t<style>\/*! elementor - v3.5.0 - 12-12-2021 *\/\n.elementor-widget-image{text-align:center}.elementor-widget-image a{display:inline-block}.elementor-widget-image a img[src$=\".svg\"]{width:48px}.elementor-widget-image img{vertical-align:middle;display:inline-block}<\/style>\t\t\t\t\t\t\t\t\t\t\t\t<img width=\"640\" height=\"256\" src=\"http:\/\/127.0.0.1\/wordpress\/wp-content\/uploads\/2021\/12\/maze-2264_640.jpg\" class=\"attachment-large size-large\" alt=\"\" loading=\"lazy\" srcset=\"http:\/\/127.0.0.1\/wordpress\/wp-content\/uploads\/2021\/12\/maze-2264_640.jpg 640w, http:\/\/127.0.0.1\/wordpress\/wp-content\/uploads\/2021\/12\/maze-2264_640-300x120.jpg 300w\" sizes=\"(max-width: 640px) 100vw, 640px\" \/>\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-3db8929d elementor-widget elementor-widget-text-editor\" data-id=\"3db8929d\" data-element_type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t<style>\/*! elementor - v3.5.0 - 12-12-2021 *\/\n.elementor-widget-text-editor.elementor-drop-cap-view-stacked .elementor-drop-cap{background-color:#818a91;color:#fff}.elementor-widget-text-editor.elementor-drop-cap-view-framed .elementor-drop-cap{color:#818a91;border:3px solid;background-color:transparent}.elementor-widget-text-editor:not(.elementor-drop-cap-view-default) .elementor-drop-cap{margin-top:8px}.elementor-widget-text-editor:not(.elementor-drop-cap-view-default) .elementor-drop-cap-letter{width:1em;height:1em}.elementor-widget-text-editor .elementor-drop-cap{float:left;text-align:center;line-height:1;font-size:50px}.elementor-widget-text-editor .elementor-drop-cap-letter{display:inline-block}<\/style>\t\t\t\t<!-- wp:image {\"id\":124,\"sizeSlug\":\"full\",\"linkDestination\":\"none\"} -->\n<figure class=\"wp-block-image size-full\"><\/figure>\n<!-- \/wp:image --><!-- wp:paragraph -->\n<p>I\u2019ve never been completely sold on Cyclomatic Complexity as a metric, it maps to linearly independent paths through code which may be useful to get an indication on the level of testing an application needs, assuming code coverage is not available (another metric that needs to be treated with caution), but how much value is that? Most applications are multi threaded and do not run in a linear fashion, I\u2019d argue that there\u2019s considerably more value in measuring the readability of code in order to allow people to understand what it does and how to change it. I\u2019ve seen easy-to-read and hard-to-read methods that evaluate to the same value on the Cyclomatic Complexity scale. Perhaps that\u2019s ok and we care about logical complexity, but my (weakly held) strong opinion is that the real value is in ease of human understanding when it comes to code.<\/p>\n<!-- \/wp:paragraph --><!-- wp:paragraph -->\n<p>Perhaps Cyclomatic Complexity has a place as an indicator of worsening or improving code complexity, but I\u2019m happy to say that I have found something that comes a lot closer to evaluating \u201ccan I work out what it\u2019s doing?\u201d type complexity, in my mind at least.<\/p>\n<!-- \/wp:paragraph --><!-- wp:paragraph -->\n<p>As part of some work that we\u2019re doing on metrics, I had a look into alternative code complexity measure and stumbled upon Cognitive Complexity \u2013 a metric that SonarQube, amongst others presumably, can report.<\/p>\n<!-- \/wp:paragraph --><!-- wp:paragraph -->\n<p>Now before moving on, I\u2019m assuming that there\u2019s little disagreement that \u201cinternal code quality\u201d (of which readability is an aspect) is a valuable thing. If not, stop reading and go here:\u00a0<a href=\"https:\/\/martinfowler.com\/articles\/is-quality-worth-cost.html\">https:\/\/martinfowler.com\/articles\/is-quality-worth-cost.html<\/a>\u00a0<\/p>\n<!-- \/wp:paragraph --><!-- wp:paragraph -->\n<p>So what is Cognitive Complexity? Other than being obviously how hard something is to get your head around. Well there\u2019s a great whitepaper\u00a0<a href=\"https:\/\/www.sonarsource.com\/resources\/white-papers\/cognitive-complexity.html\">here<\/a>, but I\u2019ll try to summarise the content below.<\/p>\n<!-- \/wp:paragraph --><!-- wp:paragraph -->\n<p>Take a look at these examples from the whitepaper:<\/p>\n<!-- \/wp:paragraph --><!-- wp:paragraph -->\n<p>\u00a0<\/p>\n<!-- \/wp:paragraph --><!-- wp:columns -->\n<div class=\"wp-block-columns\"><!-- wp:column -->\n<div class=\"wp-block-column\"><!-- wp:code -->\n<pre class=\"wp-block-code\"><code>int sumOfPrimes(int max) {              \/\/ +1<br \/>  int total = 0;<br \/>  OUT: for (int i = 1; i &lt;= max; ++i) { \/\/ +1<br \/>    for (int j = 2; j &lt; i; ++j) {       \/\/ +1<br \/>      if (i % j == 0) {                 \/\/ +1<br \/>        continue OUT;<br \/>      }<br \/>    }<br \/>    total += i;<br \/>  }<br \/>  return total;<br \/>}<\/code><\/pre>\n<!-- \/wp:code --><!-- wp:paragraph -->\n<p><strong>Cyclomatic Complexity = 4<\/strong><\/p>\n<!-- \/wp:paragraph --><\/div>\n<!-- \/wp:column --><!-- wp:column -->\n<div class=\"wp-block-column\"><!-- wp:code -->\n<pre class=\"wp-block-code\"><code>String getWords(int number) {  \/\/ +1<br \/>  switch (number) {<br \/>    case 1:                    \/\/ +1<br \/>      return \"one\";<br \/>    case 2:                    \/\/ +1<br \/>      return \"a couple\";<br \/>    case 3:                    \/\/ +1<br \/>      return \"a few\";<br \/>    default:<br \/>      return \"lots\";<br \/>    }<br \/>}<\/code><\/pre>\n<!-- \/wp:code --><!-- wp:paragraph -->\n<p><strong>Cyclomatic Complexity = 4<\/strong><\/p>\n<!-- \/wp:paragraph --><\/div>\n<!-- \/wp:column --><\/div>\n<!-- \/wp:columns --><!-- wp:paragraph -->\n<p>Which is easier to read and understand? In fact, which is actually more complex and which would need more testing?<\/p>\n<!-- \/wp:paragraph --><!-- wp:paragraph -->\n<p>Here are the same code snippets measured with the Cognitive Complexity metric:<\/p>\n<!-- \/wp:paragraph --><!-- wp:columns -->\n<div class=\"wp-block-columns\"><!-- wp:column -->\n<div class=\"wp-block-column\"><!-- wp:code -->\n<pre class=\"wp-block-code\"><code>int sumOfPrimes(int max) {<br \/>  int total = 0;<br \/>  OUT: for (int i = 1; i &lt;= max; ++i) { \/\/ +1<br \/>    for (int j = 2; j &lt; i; ++j) {       \/\/ +2<br \/>      if (i % j == 0) {                 \/\/ +3<br \/>        continue OUT;                   \/\/ +1<br \/>      }<br \/>    }<br \/>    total += i;<br \/>  }<br \/>  return total;<br \/>}<\/code><\/pre>\n<!-- \/wp:code --><!-- wp:paragraph -->\n<p><strong>Cognitive Complexity = 7<\/strong><\/p>\n<!-- \/wp:paragraph --><\/div>\n<!-- \/wp:column --><!-- wp:column -->\n<div class=\"wp-block-column\"><!-- wp:code -->\n<pre class=\"wp-block-code\"><code>String getWords(int number) {<br \/>  switch (number) {            \/\/ +1<br \/>    case 1:<br \/>      return \"one\";<br \/>    case 2:<br \/>      return \"a couple\";<br \/>    case 3:<br \/>      return \"a few\";<br \/>    default:<br \/>      return \"lots\";<br \/>    }<br \/>}<\/code><\/pre>\n<!-- \/wp:code --><!-- wp:paragraph -->\n<p><strong>Cognitive Complexity = 1<\/strong><\/p>\n<!-- \/wp:paragraph --><\/div>\n<!-- \/wp:column --><\/div>\n<!-- \/wp:columns --><!-- wp:paragraph -->\n<p>\u2026 that\u2019s more like it.<\/p>\n<!-- \/wp:paragraph --><!-- wp:paragraph -->\n<p>How is this done? There are three basic rules<\/p>\n<!-- \/wp:paragraph --><!-- wp:paragraph -->\n<p><strong>Ignore Structures that allow multiple statements to be readably shorthanded into one.<\/strong><\/p>\n<!-- \/wp:paragraph --><!-- wp:paragraph -->\n<p>A good example of this is the breaking up of code into methods to increase readability. As a result, Cognitive Complexity does not increment for methods as Cyclomatic Complexity does.<\/p>\n<!-- \/wp:paragraph --><!-- wp:paragraph -->\n<p>The aim here is to not penalise good programming practice like an increased number of smaller methods, because it is likely to reduce complexity for a reader.<\/p>\n<!-- \/wp:paragraph --><!-- wp:paragraph -->\n<p><strong>Increment when flow-breaking structures are nested<\/strong><\/p>\n<!-- \/wp:paragraph --><!-- wp:paragraph -->\n<p>Nested breaks in flow increase count as a proportion of how deeply they are nested. So a new \u201cif\u201d that is nested 4 deep adds 5 to the complexity score. 1 for the \u201cif\u201d and 4 for the nest level.<\/p>\n<!-- \/wp:paragraph --><!-- wp:paragraph -->\n<p>This is because it\u2019s intuitively easier to follow a linear list of code breaks than an equally, Cyclomatic Complexity-wise, complicated nested set of code breaks.<\/p>\n<!-- \/wp:paragraph --><!-- wp:paragraph -->\n<p><strong>Increment for each break in the linear flow of the code<\/strong><\/p>\n<!-- \/wp:paragraph --><!-- wp:paragraph -->\n<p>Anything that breaks the top to bottom, left to right flow of the code increases Cognitive Complexity, similarly to Cyclic Complexity, but there are some interesting differences.<\/p>\n<!-- \/wp:paragraph --><!-- wp:paragraph -->\n<p>1.\u00a0\u00a0\u00a0\u00a0\u00a0\u201cCatch\u201d is added as a break in flow<\/p>\n<!-- \/wp:paragraph --><!-- wp:paragraph -->\n<p>2.\u00a0\u00a0\u00a0\u00a0\u00a0\u201cElse\u201d, \u201cElif\u201d and other alternatives to the initial \u201cif\u201d break in flow do increment but not with the same nesting penalty as above, as the nesting complexity is considered paid already at the initial \u201cif\u201d.<\/p>\n<!-- \/wp:paragraph --><!-- wp:paragraph -->\n<p>3.\u00a0\u00a0\u00a0\u00a0\u00a0\u201cSwitch\u201d statements only incur a single increment, regardless of cases. Switch statements are considered more understandable then multiple \u201cif\u201d\/\u201delse if\u201d blocks.<\/p>\n<!-- \/wp:paragraph --><!-- wp:paragraph -->\n<p>4.\u00a0\u00a0\u00a0\u00a0\u00a0Repeating logical comparisons with the same logic operator only increment complexity once. This is because it\u2019s fairly similar effort to understand both of the following lines<\/p>\n<!-- \/wp:paragraph --><!-- wp:paragraph -->\n<p><code>a &amp;&amp; b<\/code><\/p>\n<!-- \/wp:paragraph --><!-- wp:paragraph -->\n<p><code>a &amp;&amp; b &amp;&amp; c &amp;&amp; d<\/code><\/p>\n<!-- \/wp:paragraph --><!-- wp:paragraph -->\n<p>but much harder to understand a statement with mixed logical operators<\/p>\n<!-- \/wp:paragraph --><!-- wp:paragraph -->\n<p><code>a || b &amp;&amp; c || d<\/code><\/p>\n<!-- \/wp:paragraph --><!-- wp:paragraph -->\n<p>5.\u00a0\u00a0\u00a0\u00a0\u00a0Recursion is the one exception to the \u201cdon\u2019t increment for methods\u201d rule<\/p>\n<!-- \/wp:paragraph --><!-- wp:paragraph -->\n<p>6.\u00a0\u00a0\u00a0\u00a0\u00a0\u201cgoto\u201d, \u201cbreak\u201d and \u201ccontinue\u201d increase complexity, but no other jumps are. e.g. an early \u201creturn\u201d is considered to make code clearer so is ignored.<\/p>\n<!-- \/wp:paragraph --><!-- wp:paragraph -->\n<p>The white paper referenced above is not long and I highly recommend reading it, but I hope that this is a useful summary (if nothing else, writing this caught a couple of mis-conceptions I\u2019d made from just reading the paper).<\/p>\n<!-- \/wp:paragraph --><!-- wp:paragraph -->\n<p>Thanks for reading!<\/p>\n<!-- \/wp:paragraph -->\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t","protected":false},"excerpt":{"rendered":"<p>Complexity as a software metric I\u2019ve never been completely sold on Cyclomatic Complexity as a metric, it maps to linearly independent paths through code which may be useful to get an indication on the level of testing an application needs, assuming code coverage is not available (another metric that needs to be treated with caution), [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":124,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":[],"categories":[6,8],"tags":[],"_links":{"self":[{"href":"http:\/\/127.0.0.1\/wordpress\/wp-json\/wp\/v2\/posts\/123"}],"collection":[{"href":"http:\/\/127.0.0.1\/wordpress\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/127.0.0.1\/wordpress\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/127.0.0.1\/wordpress\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/127.0.0.1\/wordpress\/wp-json\/wp\/v2\/comments?post=123"}],"version-history":[{"count":4,"href":"http:\/\/127.0.0.1\/wordpress\/wp-json\/wp\/v2\/posts\/123\/revisions"}],"predecessor-version":[{"id":182,"href":"http:\/\/127.0.0.1\/wordpress\/wp-json\/wp\/v2\/posts\/123\/revisions\/182"}],"wp:featuredmedia":[{"embeddable":true,"href":"http:\/\/127.0.0.1\/wordpress\/wp-json\/wp\/v2\/media\/124"}],"wp:attachment":[{"href":"http:\/\/127.0.0.1\/wordpress\/wp-json\/wp\/v2\/media?parent=123"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/127.0.0.1\/wordpress\/wp-json\/wp\/v2\/categories?post=123"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/127.0.0.1\/wordpress\/wp-json\/wp\/v2\/tags?post=123"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}