On Monday, 29 July 2013 at 19:38:51 UTC, Walter Bright wrote:
On 7/29/2013 12:08 PM, JS wrote:
Trying to use distance and speed as a measure of performance of a program is
just ridiculous.


If you google "program execution speed" you'll find it's a commonly used term. "Lines per second" is a common measure of compiler execution speed - google "compiler lines per second" and see.


(again, if we started with 12 second and went to 21 seconds, it would be a near
75% increase. But a 75% increase is not a 75% decrease!!!!!!!!)

Speed is the reciprocal of time, meaning a decrease in time is an increase in speed.

You are right, sorry. There is no difference.

I think the issue is interpretation. When I read "X% increase in speed" I think "X% faster [in time]".

Since you are using speed in a technical way, then it works. I think it is deceptive, in some sense... although not necessarily intentional.

The reason is very few people measure performance of a program in any other way than the time it takes to execute the program. That is all that matters in most cases... and in most cases lines per second mean nothing... but I guess in compilers it is more useful.


What I'm now wondering is why you chose to use % increase in speed rather than % decrease in time? Is it because it is a larger number and looks more impressive?

It think 99.9999% of people using D only care about the absolute time it takes to compile their code, and giving a number that they can actually use directly(instead of having to calculate first) seems more useful.

By knowing you *sped* up the compiler so it is 43% faster lets me know that I should expect compilation time of my code to be approximately cut in half.

When you say 75% increase in speed I have to actually do some calculation and hopefully also interpret speed properly.

Nowhere in the article do you refer to the lines per second or any technical definition of speed.

It's a somewhat informal article but you are using a rather formal definition of speed and it also does not directly give the user an obvious metric as just giving them the percentage change of time.



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