Time exchange rate

http://www.johndcook.com/blog/2014/08/17/time-exchange-rate/

by jaimebuelta • 12 years ago

30 11 12 years ago

And what about spending time to optimize a end user's time?

TeMPOraL2• 12 years ago

Exactly. If we are to stick to such calculations, then it's worth years of programmer's time to save seconds of end-user time for any remotely successful piece of software.

I wish more programmers and companies would think of that. Everything they do scales milionfold - that includes potential time savings for users as well as wasting coal on doing stupid things like parsing literally millions lines of XML for basic configuration (OSGi, I'm looking at you! Also, news for some, processor cycles cost electricity, which is not unlimited or free.). But I know - incentives, money, optimization, capitalism, Moloch!

cfallin3• 12 years ago

Yep, or even your own time if you run the program multiple times. E.g., if your code is running on a thousand machines, that CPU-hour savings that cost $0.05 now costs $50.00; past a certain point it does pay to throw engineers at insane micro-optimizations. Or nonlinear payoffs from CPU time improvements -- e.g. meeting a realtime deadline or else the system is useless. The "CPU-hour vs. engineer-hour" comparison works only when the engineer him/herself runs their own program, exactly once, without other constraints.

matt_kantor• 12 years ago

The "CPU-hour vs. engineer-hour" comparison works only when the engineer him/herself runs their own program, exactly once, without other constraints.

Or when the system is designed such that you can scale hardware to decrease run time. Sometimes the choice is between throwing programmer time at a performance problem or throwing hardware at it, and often the economics work out in favor of the latter.

fleitz2• 12 years ago

That depends entirely on how much the client is paying. Usually clients don't value their time very much.

TTPrograms• 12 years ago

One metric I think about a lot in my work is the sum of runtime and programming time, because I often write one-off analysis programs and just care about when I get the results. It's nice because I can focus on the sweeping optimizations and not the small ones.

retroencabulato• 12 years ago

Cute, but there are a lot of situations where this breaks down. It assumes that a programmer's efficiency is independent of a program's efficiency.

If I have to wait hours for a job to complete that could be completed in moments with a bit of extra work, there certainly is value in working on the optimisation.

fleitz2• 12 years ago

Yes! I can't stand this kind of thinking in code reviews, someone will say X is slow, and I say, "How slow is it?" they'll say something about O(X) and I'll say, no really exactly how much time in seconds will be saved by changing this.

Usually at this point they have no answer.

In general your O(n^4) algo is perfectly fine, and no one will ever notice your O(1) replacement. When it isn't fine it's painfully clear that it's not OK.

Time exchange rate

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