In article <mailman.4929.1388896998.18130.python-l...@python.org>, Rustom Mody <rustompm...@gmail.com> wrote:
> On Sun, Jan 5, 2014 at 8:50 AM, Roy Smith <r...@panix.com> wrote: > > I wrote: > >> > I realize I'm taking this statement out of context, but yes, sometimes > >> > fast is more important than correct. > > > > In article <52c8c301$0$29998$c3e8da3$54964...@news.astraweb.com>, > > Steven D'Aprano <steve+comp.lang.pyt...@pearwood.info> wrote: > >> Fast is never more important than correct. > > > > Sure it is. > > > > Let's imagine you're building a system which sorts packages for > > delivery. You sort 1 million packages every night and put them on > > trucks going out for final delivery. > > > > Some assumptions: > > > > Every second I can cut from the sort time saves me $0.01. > > > > If I mis-sort a package, it goes out on the wrong truck, doesn't get > > discovered until the end of the day, and ends up costing me $5 > > (including not just the direct cost of redelivering it, but also > > factoring in ill will and having to make the occasional refund for not > > meeting the promised delivery time). > > > > I've got a new sorting algorithm which is guaranteed to cut 10 seconds > > off the sorting time (i.e. $0.10 per package). The problem is, it makes > > a mistake 1% of the time. > > > > Let's see: > > > > 1 million packages x $0.10 = $100,000 saved per day because I sort them > > faster. 10,000 of them will go to the wrong place, and that will cost > > me $50,000 per day. By going fast and making mistakes once in a while, > > I increase my profit by $50,000 per day. > > > > The numbers above are fabricated, but I'm sure UPS, FexEx, and all the > > other package delivery companies are doing these sorts of analyses every > > day. I watch the UPS guy come to my house. He gets out of his truck, > > walks to my front door, rings the bell, waits approximately 5 > > microseconds, leaves the package on the porch, and goes back to his > > truck. I'm sure UPS has figured out that the amortized cost of the > > occasional stolen or lost package is less than the cost for the delivery > > guy to wait for me to come to the front door and sign for the delivery. > > > > Looking at another problem domain, let's say you're a contestant on > > Jeopardy. If you listen to the entire clue and spend 3 seconds making > > sure you know the correct answer before hitting the buzzer, it doesn't > > matter if you're right or wrong. Somebody else beat you to the buzzer, > > 2.5 seconds ago. > > > > Or, let's take an example from sports. I'm standing at home plate > > holding a bat. 60 feet away from me, the pitcher is about to throw a > > baseball towards me at darn close to 100 MPH (insert words like "bowl" > > and "wicket" as geographically appropriate). 400 ms later, the ball is > > going to be in the catcher's glove if you don't hit it. If you have an > > absolutely perfect algorithm to determining if it's a ball or a strike, > > which takes 500 ms to run, you're going back to the minor leagues. If > > you have a 300 ms algorithm which is right 75% of the time, you're > > heading to the hall of fame. > > > Neat examples -- thanks > Only minor quibble isnt $5 cost of mis-sorting a gross underestimate? I have no idea. Like I said, the numbers are all fabricated. I do have a friend who used to work for UPS. He told me lots of UPS efficiency stories. One of them had to do with mis-routed packages. IIRC, the process for dealing with a mis-routed package was to NOT waste any time trying to figure out why it was mis-routed. It was just thrown back into the input hopper to go through the whole system again. The sorting software kept track of how many times it had sorted a particular package. Only after N attempts (where N was something like 3), was it kicked out of the automated process for human intervention. -- https://mail.python.org/mailman/listinfo/python-list
