@jameslo Yes, this is unfortunate.

Another way to approach this, although not really solving the issue, would be to decouple the array the algorithm is operating on from the visual display.

Here i added a second array and the visuals are just performed by pipes: quicksort with delay.pd

So the algorithm is carried out immediately on the first array, but the display on the graphic array is delayed.

@ingox Nice!

A good exercise here might be to consider an approach where [until] could be swapped out with a [metro] or an abstraction around [metro] to get the same interface.

Using [metro] will cause the steps of the loop to be executed by Pd's scheduler. At that point you'll get the GUI updates you're looking for, at any speed you specify for the metronome.