Enormous Input and Output Test

Bearophile bearophileHUGS at lycos.com
Sun Oct 4 12:06:01 CEST 2009

Terry Reedy:

> Don't waste your time with problem sites that judge raw-clock time over
> (and before) accuracy, thereby greatly favoring low-level languages and
> hack tricks over clear high-level code.

I usually don't like to solve the kind of problems shown by those
sites because those problems are too much artificial (and often too
much difficult). But sometimes I have written some solutions.

But those sites never judge "raw" running time over accuracy: in most
or all such sites the programs are tested with tons of possible
inputs, and if even one output is a bit wrong, the program is totally
refused. This is a hard rule that encourages programmers to take a
very good care of program correctness.

Some sites add a little more "noise" in the inputs, simulating a bit
more real-world inputs, while most of those online contests give clean
inputs (the input bounds are well specified in the problem statement).

>From what I've seen from some of the best solutions submitted to those
sites (some sites allow people to see the source of the contest
entries), the programs usually don't (need to) use "hack tricks" as
you say (even if probably some program uses them). Using hacks is
often unsafe so people usually prefer safer ways to code, because just
a little bug may fully compromise the score of the program.

I agree that the timing scores in such sites often encourage low level
languages, like C (and sometimes C++, that's a multilevel language),
but on the other hand such languages exist, C is used in many real-
world places, so designing sites where people compete with such
languages is legit. C allows people to understand better what's going
on inside the computer, this is valuable and positive. Bashing low-
level languages is silly. Even CPython is written in C. A good
programmer has to know both higher and lower level languages.

And in real-life sometimes you need performance. This thread shows
that a normal Python program is not up to those timings for the
enormous input problem (even if there are ways to write a Python
program to solve this problem). People at Google are trying to create
a 5 times faster Python (Unladen Swallow project) because they use lot
of real-world Python code and they think Python is slow. I've found
plenty of situations where CPython code is not fast enough for my


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