Tuesday, November 21, 2006

Queuing Theory

Queuing Theory

We spend a lot of time in queues. Life is a queue itself. You get stuck at traffic jams, for somebody to approve a request, lines at stores, waiting for your mother in law to call, or for rain to wash your car.

Queuing theory deals with making your wait as short as possible. One hotel used its front help desk to route people to specific elevator which takes them to their destination floor (reducing waste). “Take # 3 it takes to 10th floor faster…”

The main measurement of a queue is cycle time – that is, the average time it takes something to get from one end of a process to the other. Nine months for a baby to come into this world. Sometimes if they come 2 months earlier they can play for another soccer team.

Today we worked on queuing jobs that are behaving badly. The time spent waiting in the queue is wasted time. There are two ways to reduce cycle time (I hate to limit to two); one is to look at the way work arrives and the other is to look at the way work is processed. Doctor’s office use reservation system to assure that patients arrive at regular intervals.

One way to control the rate of work arrival is to make sure small arrival of requests, if the same work is released in small batches, the queue can be much smaller. However, the other way is to go after fixing the processor – which is faster service (it is not in our control).

Next time you are waiting at store pay attention which cashier service faster. The first criterion (managing arrival) is natural assuming you are picking the leveled and shorter line by default.

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