When to ask REU professor for recommendation?

[prospectivecsgrad]

I recently completed an REU, and while I don't think I'll get a publication from it, I still think I want to ask one of the people (if not two) for a recommendation for when I eventually apply for CS PhD programs.  Generally, when is the best time to do so, as I am taking a gap year after graduating at the end of this year.

[PicoHenries]

You should definitely ask them now, while you're fresh in their minds. At best, they'll hold on to the letter for you until you need it. At worst, they don't write it right away and you can just ask again closer to the time of your applications.