Comments on: Database Questions for 2010: What’s On My Mind

By: Kevembuangga

Kevembuangga — Wed, 06 Jan 2010 00:17:35 +0000

I had to fix this once myself.

OK, fix that C one:

for (i = size – 1; i;) {
for (j = i; ++j < size && a[j-1] > a[j]; swap(a[j-1], a[j]));
while (–i && a{i] <= a[i+1]);
}

By: Daniel Lemire

Daniel Lemire — Tue, 05 Jan 2010 13:24:27 +0000

@Bannister

Yes, you are quite right. By lightweight, I mean that it reduces the computational cost.

By: Preston L. Bannister

Preston L. Bannister — Tue, 05 Jan 2010 06:39:12 +0000

More exactly, by “lightweight” you mean “compute-cost-effective” compression. Can compression save CPU cycles? Maybe. Sometimes. Would be good to explore and map that dimension somewhat.

By: Itman

Itman — Tue, 05 Jan 2010 06:20:19 +0000

Chances are huge! I had to fix this once myself. The premature optimization problem arises usually, when there are two comparable algorithms and you chose a more complicated. Then, of course, it is a waste of time. But to chose the right algorithm, you should first understand the problem. That requires some CS knowledge. Moreover, Moore’s law would not hold forever. Sooner or later you have to optimize to get this 10 or 50 percent increase. In some applications such as large-scale applications (e.g. web search), you have to do this already.

By: Kevembuangga

Kevembuangga — Tue, 05 Jan 2010 06:06:19 +0000

Unfortunately, quite often their code contains such horrible jokes as bubble sort. Which, in turn, other folks have to debug and to fix.

Debugging bubble sort?
What are the chances that a bug show up in bubble sort relative to any other sort?
It’s ugly and horrendously inefficient but if you have a dozen items to sort it could be that it IS the right solution.
You didn’t really grok the points in the linked comment, did you?

By: Itman

Itman — Mon, 04 Jan 2010 21:44:40 +0000

I just love these arrogant people who think that CS education and academia are useless. Of course, only they — real warriors — save the world and write the code. Unfortunately, quite often their code contains such horrible jokes as bubble sort. Which, in turn, other folks have to debug and to fix.

By: Daniel Lemire

Daniel Lemire — Mon, 04 Jan 2010 18:54:22 +0000

@Kevembuangga

Good points.

You may enjoy this blog post by Maarten van Emden on “What is Computer Science?”

http://vanemden.wordpress.com/2009/12/27/what-is-computer-science/

By: Kevembuangga

Kevembuangga — Mon, 04 Jan 2010 18:24:11 +0000

Don’t bother!
There are cheaper ways to improve software performance
CS research is mostly another form of “mathematical disease”.
Oh! Happy New Year nevertheless…