Is there a way to evaluate two algorithms?

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Is there a way to evaluate two algorithms to decide which is best? Two algorithms are use for solve the same equation in two deferent ways.

Posted 23-Mar-11 23:39pm

Panchaz

Updated 23-Mar-11 23:43pm

v3

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3 solutions

Solution 2

Yes, run a test: feed the two algorithms with the same input data (making sure the output is correct) and measure performance.

Posted 24-Mar-11 0:17am

CPallini

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OriginalGriff 24-Mar-11 6:28am

:thumbsup:

Sergey Alexandrovich Kryukov 24-Mar-11 12:53pm

Strictly speaking, as OP asks about "best" (not fastest), only Griff's answer is correct.

CPallini 24-Mar-11 14:04pm

You're right: he used the 'quickest' term. :-D

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OriginalGriff · Accepted Answer · 2011-03-23T23:57:00

Solution 1

No.

You first have to define "best": Best for a sort algorithm might be "fastest": but even then "fastest" will depend on data - if you know the data has a particular pattern, then the "fastest" general algorithm may not be the quickest to sort the specific data.

Posted 23-Mar-11 23:57pm

OriginalGriff

Comments

Panchaz 24-Mar-11 6:21am

This algorithms are use for search trees so both algorithms will be searching the same tree

OriginalGriff 24-Mar-11 6:27am

So, do as Carlo suggests: check them and see...

Sergey Alexandrovich Kryukov 24-Mar-11 12:52pm

Best answer. Order "best" on the set of algorithms is not defined. Period.
--SA

Sergey Alexandrovich Kryukov 24-Mar-11 12:54pm

After looking at other answers, I also see this one the only correct one, my 5.
--SA

Espen Harlinn · Accepted Answer · 2011-03-24T00:29:00

Solution 3

If there are open-source implmentations available, and there usually are - test that each of them is capable of correct behaviour - sometimes some algorithms are not able to evaluate all possible inputs - so it's a good idea to check that they have the desired behaviour.

You may be interested in Big O Notation[^] - it's used to say something about the performance characteristics of an algorithm.

For some algorithms there is a significant difference between best case and worst case - can you live with the worst case?

Trial runs using realistic input data may in the end be your best choice.

Regards
Espen Harlinn

Posted 24-Mar-11 0:29am

Espen Harlinn

Comments

Sergey Alexandrovich Kryukov 24-Mar-11 12:54pm

This is good information, my 5, but, strictly, speaking, only Griff provided a correct answer, see my comment.
--SA

Espen Harlinn 24-Mar-11 17:02pm

He might have taken into account that various algorithms have their limitations - I'm kind of assuming that we are talking about something beyond quicksort vs buble sort - where the worst case may be that one algorithm may run forever as in n! - while another may give an approximate optimal result - or actually be able to determine that no satisfactory result can be found based on the input. This is not unusual when evaluating various optimization methods.

Sergey Alexandrovich Kryukov 24-Mar-11 21:20pm

Nobody argues against evaluation. I'm making a point of formality. I hope you familiar with the concept of mathematical order theory called partially ordered set. The term "best" suggests there is an implied (at least) partial order over the set of algorithms. Nobody define such order and I seriously suspect such order is impossible to build (impossible to satisfy axioms of partial order).

You mention of infinite algorithms give us a hint why such order is impossible. You could also remember a halting problem which is not computable. One algorithm could be faster with some data and infinite with other and other pathological cases...

--SA

Espen Harlinn 25-Mar-11 4:34am

Right, that would definitely be the worst case :)

Sergey Alexandrovich Kryukov 25-Mar-11 12:32pm

This is just for example...
--SA