Big problem: which queue to choose? Having learnt about Queuing Theory at school, and knowing that single queue-multiple consumer is as efficient as it gets, it's always an agonizing decision. You have to balance a number of factors: how many people in the queue, how many items do people want to buy, do they look impatient or vagued out. It's better to be behind a person buying 10 of one thing, than one item of ten different things. And, although it pains me to admit it, old people are Bad News. Statistically, you'll waste 30 seconds to five minutes with them in front of you.
So I was pondering this the other day, and reflecting on my worldview, how I tend to algorithmatise things (figuring out the shortest path between the four shops I need to go to, establishing contigency plans in case a shop doesn't have a product I need, that sort of stuff. When house-cleaning I try to keep my hands full. I hate going into room A to fetch something for room B, and realising there was something in room B which should be tidied away in room A). Geeking out, basically.
And as I stood there ruminating on this, I was idly watching the woman at the front of the line, and became more and more alarmed. She was just stacking up the products that the cashier swiped...but not putting them into bags. I couldn't figure out what she was doing, but figured it was bad news for me. And on and on it went, until the cashier had checked out every last item. Then she handed over her credit card, had it swiped, punched in her pin, and only once she had received her docket did she begin to bag up the stuff she'd bought. And I thought "You f5cking moron: can't you deal with asynchronous events?" Because the cashier couldn't start checking out the items of the next person until she'd cleared the decks. Which took a non-trivial amount of time, during which no other work could be done.
Meantime I note that the people who were at the ends of the other queues are now close to being served, and I've still got two people in front of me. But I'm in too deep at this point to bear the cost of cutting my losses and requeuing on another line.
The next person went through without a hitch: a few items, had cash ready, out straight away.
Then the person in front of me went through. Seemed to be okay: started bagging up the goods as soon as they came through, but she had a fair number of things to buy. Then it turns out that she has a Method. All the fruit goes together, the stuff that requires Refrigeration goes together, tins kept apart from packets and so on. And the cashier is done quickly and announces the price. But does she do anything? Noooooooooo! She just keeps putting stuff in bags. And the cashier, who is polite (the Customer is always Right and all that) says nothing.
At this point I just take a deep breath and resign myself. The people who were at the ends of the other queues are all long since gone. At times like this I can't help thinking that a lot of what we learn in Computer Science is applicable to the Real World. And one of the cardinal sins is stalling the pipeline. When you have people queued up to do something, you want to get in and get out as fast as possible, just like an instruction on a CPU. Because wait states are just time lost. Gone, never to come back.
I really, really hate when that happens.