Blog "about python 3"

[Roy Smith]

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$5496439d at news.astraweb.com>,
 Steven D'Aprano <steve+comp.lang.python at 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.