A single line to 3 cashiers is ~3x faster than a separate line for each cashier

Post by nik_0_0 » Thu, Dec 08, 2011, 7:56 PM UTC

philwelch wrote: post #73

rdtsc wrote: post #43

Earlier quoted context omitted.

Not trying to be condescending but doesn't it surprise anyone here that this is _not_ obvious? At least on this site, there are still people doubting or debating this. So I am wondering why don't stores do this already. And I believe it is because of perceptions. They understand that time will be saved, however, they realize that most people will be scared by a long line. One long line that moves fast will still appe…

It's another instance of "people are stupid". Yes, for any educated person it's obvious that one line is faster, that's the first thing about queueing theory, but most people don't know the first thing about queueing theory. Other instances of "people are stupid" leading to poor design: * Some cars come with a CVT (continuously variable transmission) rather than having to shift gears. The audible pitch of the engine…

Post by gujk » Thu, Dec 08, 2011, 8:16 PM UTC

alsocasey wrote: post #108

MaysonL wrote: post #90

Earlier quoted context omitted.

But of course this is BS, because the three queues are not independent. Try it with 1 queue which feeds into whichever of the three queues is currently shortest. And of course, in grocery stores, where one can unload one's cart while the person ahead is being processed, there's an advantage to multiple lines.

Isn't this essentially equivalent to having a single queue though... except now you have a kind of cache at each register holding a small number of customers?

Post by narkee » Thu, Dec 08, 2011, 8:22 PM UTC

dxbydt wrote: post #79

scala> import org.apache.commons.math.distribution.{ExponentialDistributionImpl=>expo} //pc = process customer, with a mean time mu per customer scala> def pc(mu:Int):Double= new expo(mu).sample // q = queue of n customers with mean process time mu scala> def q(n:Int,mu:Int):Double=(1 to n).map(_=>pc(mu)).sum scala> // put 3000 people in 1 queue with mean process time 50 scala> (1 to 1000).map(_=>q(3000,50)).sum/1000…

Post by gujk » Thu, Dec 08, 2011, 8:30 PM UTC

brown9-2 wrote: post #110

pnathan wrote: post #27

FYI: This is an example of the branch of mathematics called queueing theory. http://en.wikipedia.org/wiki/Queueing_theory It's a fascinating study requiring a good knowledge of probability to use beyond the simplified models. It turns out from the math that throughput using a single queue is better than using multiple queues.

This is a bit of an aside, but something I've always wondered is: why does this branch of mathematics get labeled as Queueing "theory"? From my brief understanding, when someone talks about Queueing theory they are not talking about a singular "theory" but they mean something much broader. It doesn't seem as if there is something here that needs to be proved or disproved. This is a part of naming in mathematics that…

Post by hn_reader » Thu, Dec 08, 2011, 8:31 PM UTC

prodigal_erik wrote: post #93

cheald wrote: post #74

Earlier quoted context omitted.

Fry's Electronics does the single line thing, and any time there is a line, I feel like I end up standing in it longer than I would at a grocery story. I suspect this is probably psychological, but letting me, as the shopper, pick the line I want to stand in puts me in charge of how long I wait. If I pick a bad line, it's my fault for picking the bad line. When there's just one line available, I don't get that choice…

When I have to choose a line I find myself harshly judging the people around me, because every difference can impose a cost in boredom and lost leisure time. "This guy's old and worn out. They seem kind of foreign, won't understand the cashier. That one looks poor, probably uses a lot of coupons and argues about what's discounted. They're paying all their attention to their kid instead of getting out of everyone's wa…