<p>I just want to add that from the algorithm point of view (i.e. the cost only considers the number of comparisons and swaps), 2-pivot quicksort and 3-pivot quicksort is not better than classical quicksort (which uses 1 pivot), if not worse. 
However, they are faster in practice since they take the benefits of modern computer architecture. Specifically, their numbers of cache misses are smaller. So if we remove all caches and there are only CPU and main memory, in my understanding, 2/3-pivot quicksort is worse than classical quicksort.</p>

<p>References:
3-pivot Quicksort: <a href="https://epubs.siam.org/doi/pdf/10.1137/1.9781611973198.6" rel="noreferrer">https://epubs.siam.org/doi/pdf/10.1137/1.9781611973198.6</a>
Analysis of why they perform better than classical Quicksort: <a href="https://arxiv.org/pdf/1412.0193v1.pdf" rel="noreferrer">https://arxiv.org/pdf/1412.0193v1.pdf</a>
A complete and not-too-much-details reference: <a href="https://algs4.cs.princeton.edu/lectures/23Quicksort.pdf" rel="noreferrer">https://algs4.cs.princeton.edu/lectures/23Quicksort.pdf</a></p>
What's the difference of dual pivot quick sort and quick sort?
<p>I've never seen dual pivot quick sort before.
Is it an upgraded edition of quick sort?<br>
And what is the difference between dual pivot quick sort and quick sort?</p>