is it possible that answers can be accepted?

https://in.mathworks.com/matlabcentral/answers/51645-how-to-find-out-if-a-number-is-even-or-not#comment_620508 if you click the link you will notice that two answers are accepted , found it quite interesting . Does anybody know how the system works?

[madhan ravi]

it would be better if any MVP's clarify

[KALYAN ACHARJYA]

@madhan sir Agreed!

[madhan ravi]

Thank you @ Kalyan

[Adam Danz]

+1, I always wondered about this, too.

[Dyuman Joshi]

I am unable to find the solution (or any comment as well) from the user whose name is shown in highlight on the top as the accepted answer (Thomas, Level 6) on the problem.

Weird.

[Jan]

If the system is state of the art, the data base of the forum runs on several computers. Then databases can be ACID proof (atomicity, consistency, isolation, and durability, see e.g. here), but Matlab answers is not, obviously. If two events are triggered within a certain amount of time, the different servers cannot consider the side effects. In this case accepting an answer should block further acceptings, but it needs some time to distribute the new state.

Well, ACID proof distributed databases are available for decades now.

Answer 1

[John D'Errico]

Being an MVP does not give you the privilege to doubly accept an answer. Read the help for Answers. It tells you what privileges are accrued with increasing rep.

https://www.mathworks.com/matlabcentral/answers/help?s_tid=gn_mlc_ans_hlp

As I recall, occasionally two answers can get accepted, if two acceptances are registered at the same time, before the database knows what has happened. The OP can always accept an answer immediately. Once accepted, that locks other answers out from being accepted.

If the OP has not accepted an answer within 7 days, then all answers are opened up for acceptance, by users with sufficient site rep. (500 rep is all that is needed, based on the rep privileges listed in the help.) I gather this is when a double acceptance can rarely occur, if then TWO answers are accepted within a sufficiently short span of time.

[madhan ravi]

” I gather this is when a double acceptance can rarely occur, if then TWO answers are accepted within a sufficiently short span of time“

Perfect exactly what I was looking for , thank you @John D ‚Errico :)

[Image Analyst]

You recall correctly John. Basically if a poster clicks "Accept this answer" on two Answers like a second apart, it can happen that both will be accepted. Basically a timing glitch.

[KALYAN ACHARJYA]

@John ohh Great. Thank you

[Jan]

That multiple answers can be accepted within a certain period of time means, that the database is not ACID proof, see https://en.wikipedia.org/wiki/ACID_(computer_science) . This is not state of the art and can cause a corruption of the data beyond inoffensive effects like double accepting. The ACID model was developed in 1983, see e.g. ISO/IEC 10026-1:1992 Section 4.

If an account with a high-reputation is cracked, a distributed attack could flood the database with contradictory information, which are hard to fix automatically.

[madhan ravi]

Useful information @Jan

[Guillaume]

Yes, double acceptance of answers is a bug. I know that Walter Roberson reports these to MathWorks when he spots them so they're aware of it. I doubt they'd want to make the decision on which of the two should be the correctly accepted one, so both will probably stay accepted.

Answer 2

[Bruno Luong]

Can you accept this one and the previous one?

[KALYAN ACHARJYA]

+1 OK, I don't have the privilege to accept this answer.

[Image Analyst]

You can't accept Answers until at least a week has passed, unless you're the questioner, not even if you're an MVP.

[madhan ravi]

Yea sir but how two answers have been accepted in the link I posted?

[Image Analyst]

Timing issue.

[madhan ravi]

Thank you sir @Image Analyst

Answer 3

[KALYAN ACHARJYA]

Sir, Yes it is Possible, I have experienced the same.

[madhan ravi]

can you elaborate @Kalyan ?

[madhan ravi]

ok lets take our time , no problem

Answer 4

[Bruno Luong]

Can you accept this one and the next one?

[madhan ravi]

no I'm not able to accept it

Answer 5

[Bruno Luong]

I might win 2 points or nothing

[madhan ravi]

knew it @Bruno ?

[Bruno Luong]

haha

[madhan ravi]

ok do you know the reason?

[Bruno Luong]

Once I become MVP then I can tell you.

[madhan ravi]

indeed, we are all waiting for you to become one

[Guillaume]

I'm afraid nothing magical happens once you become an MVP other than having that little badge attached to your name. You don't get any more privilege than the ones granted by achieving the required reputation.

Achieving 2000 reputation (way before MVP) puts you on an editor mailing list where mathworks may very occasionally ask for feedback.

The little MVP badge is nice though!

[madhan ravi]

Amazing though, I have to admit that I have been sick for a couple of days was able to manage it only because I am part if this community. Cheers