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    <p>Comparing floating point numbers for depends on the context. Since even changing the order of operations can produce different results, it is important to know how "equal" you want the numbers to be.</p> <p><a href="https://randomascii.wordpress.com/2012/02/25/comparing-floating-point-numbers-2012-edition" rel="noreferrer">Comparing floating point numbers</a> by Bruce Dawson is a good place to start when looking at floating point comparison. </p> <p>The following definitions are from <a href="http://books.google.ca/books?ei=KRkLSYLZEJ7ktQOX3-ChBQ&amp;id=T89QAAAAMAAJ&amp;dq=%22essentially+equal%22+%22approximately+equal%22+knuth&amp;q=%22essentially+equal%22+%22approximately+equal%22+%22definitely+less+than%22&amp;pgis=1#search" rel="noreferrer">The art of computer programming by Knuth</a>: </p> <pre><code>bool approximatelyEqual(float a, float b, float epsilon) { return fabs(a - b) &lt;= ( (fabs(a) &lt; fabs(b) ? fabs(b) : fabs(a)) * epsilon); } bool essentiallyEqual(float a, float b, float epsilon) { return fabs(a - b) &lt;= ( (fabs(a) &gt; fabs(b) ? fabs(b) : fabs(a)) * epsilon); } bool definitelyGreaterThan(float a, float b, float epsilon) { return (a - b) &gt; ( (fabs(a) &lt; fabs(b) ? fabs(b) : fabs(a)) * epsilon); } bool definitelyLessThan(float a, float b, float epsilon) { return (b - a) &gt; ( (fabs(a) &lt; fabs(b) ? fabs(b) : fabs(a)) * epsilon); } </code></pre> <p>Of course, choosing epsilon depends on the context, and determines how equal you want the numbers to be. </p> <p>Another method of comparing floating point numbers is to look at the ULP (units in last place) of the numbers. While not dealing specifically with comparisons, the paper <a href="http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.22.6768" rel="noreferrer">What every computer scientist should know about floating point numbers</a> is a good resource for understanding how floating point works and what the pitfalls are, including what ULP is. </p>
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    1. POWhat is the most effective way for float and double comparison?
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    1. COthanks for posting how to determine which number is smaller/bigger!
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