Delphi and Performance Coding. Statement Performance and code length results

Question

Lets simply fantasize and talk about performance.

As I have read the article in about.delphi.com called performance programming, there was interesting paragraphs claiming that Case statement ( in fact I prefer calling it as structure ) is faster than If ; For is faster than While and Repeat, but While is the slowest loop operator. I probably understand why While is the slowest, but ... what about others.

Have you tested / played / experimented or even gained real performance boost if changed, for example, all IF statements to Cases where possible?

Also I would like to talk about other - modified - loop and if statement behaviors in Delphi IDE, but it would be another question.

Shall we start, ladies and gentleman?

Please provide a link for the article you mention. I find nothing there named "Performance programming." — Rob Kennedy
– Rob Kennedy, Commented Jul 8, 2009 at 15:09

Anton Gogolev · Accepted Answer · 2009-07-08 08:05:34Z

3

It's very rare when the type of control structure/loop construct do matter. You can't possibly get any reasonable performance increase if you change, say, For loop to While loop. Rather, algorithms do matter.

answered Jul 8, 2009 at 8:05

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Anton Gogolev

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Lieven Keersmaekers · Accepted Answer · 2009-07-08 08:30:13Z

2

I doubt for will be slower in practice than while.

AFAIK, for evaluates the condition one time while while (no pun intended) evaluates the condition every time. Consider following statements

for i = 0 to GettingAmountOfUsersIsTakingALotOfTime do
begin
  ...
end;

i := 0;
while i <= GettingAmountOfUsersIsTakingALotOfTime do
begin
  ...
  Inc(I);
end;

The while statement will be magnitudes of times slower than the if statement.

answered Jul 8, 2009 at 8:30

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Lieven Keersmaekers

1 Comment

HX_unbanned Over a year ago

yes, you are absolutely correct. I did write wrong - I thought the same, but somehow wrote different ;) Anyways - thank you for tip and illustration - I hope it will help othe begginers in Delphi programming ;)

2 revs · Accepted Answer · 2017-05-23 12:16:04Z

1

This is the best response I've seen to questions like this.

edited May 23, 2017 at 12:16

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2 revs
Mike Dunlavey

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