An algorithm for perfect simulation from the unique solution of the
distributional fixed point equation Y=dâUY+U(1âU) is constructed, where
Y and U are independent and U is uniformly distributed on [0,1]. This
distribution comes up as a limit distribution in the probabilistic analysis of
the Quickselect algorithm. Our simulation algorithm is based on coupling from
the past with a multigamma coupler. It has four lines of code