[trombonechamp]

Here is a bit more realistic model of the riffle shuffle. These results show that you need between 3 to 8 riffle shuffles, depending on your skill. Notably, the number of needed shuffles actually does get lower as you get better, i.e., less clumping is better: http://blog.maxshinnpotential.com/2017/11/05/optimality-in-c...