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Friday, December 23, 2011

Round-Robin and the Elevators Scheduling at My Block

Talking about round-robin, I am reminded of the elevators at the block of flats where I live.

I've been frustrated at the elevators before. Sometimes when I call for the elevator, I can tell that 2 of the lifts are in transit (going somewhere, with or without passangers).

Sometimes only 1 out of 3 is in transit.

When I call the lifts, I expect one of the lifts that are parked to be mobilised. Instead, the logic that drives the lifts assignment lets that lift go in the opposite direction, then come to a rest, (either to drop off some passenger or park itself), then wakes itself again, to come to my level. There are many other cases of combination of the lifts doing different things mid-way, and reacted in a very inefficient manner, resulting in my having to wait a huge amount of time before a lift picks me up. Now I realise this has totally got to do with the concept of round-robin (or the lack of) assignment.

This is the same for the elevators at work. There are at least 4 elevators serving the levels of my current workplace. Most of the time I don't need to wait an awful long time to get an elevator, but sometimes they are really inefficient.

Elevators may be using another set of rules to guide the scheduling algorithm to decide upon which lifts to activate for all I know. Maybe I should go and read up a bit of elevator scheduling just to clear my doubts. :)