Hello again, is there any good websites/online forums where people discuss AMPL modeling? appreciate your suggestions...

Meanwhile, I'd like to know in AMPL,

[x] == Biggest integer lower than 'x'

How do you define the above in AMPL?

Thanks in advance

asked 11 Dec '11, 11:29

Pavan's gravatar image

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retagged 11 Dec '11, 16:49

fbahr's gravatar image

fbahr ♦


I hope Robert Fourer is in this OR-Exchange group. That certain AMPL google group has been (to my knowledge) is inactive for quite sometime. Meanwhile, let me fine tune my model first.

(12 Dec '11, 00:17) Pavan

AMPL google group is definitely active. Bob answered a question as late as today (12-dec).

(12 Dec '11, 02:06) Erling

AMPL questions should be asked in their discussion forum :

AMPL Google Group

But the outcome might be the same as asking here, since a certain fast typing Paul Rubin is answering lots of questions both here and on their forum (in fact any optimization forum :-))


answered 11 Dec '11, 11:40

Bo%20Jensen's gravatar image

Bo Jensen ♦
accept rate: 14%

I follow OR Exchange though as yet I don't have enough (%#)(#@$(^@% reputation points to use it all that effectively. Regarding the AMPL Google group, as of right now it shows 6 posts in the past 24 hours.


answered 14 Dec '11, 14:07

4er's gravatar image

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@4er: Afaik, with 41 karma points you can vote on questions and answers (up-votes only, though) and are able to edit community wikis/questions (was 100pts - but has been lowered to 30pts by @Michael Trick [btw, someone with 'super-powers' ought to update the FAQ entry on this]). 10pts left, and you are allowed to leave comments on posts. 50pts more, down-voting, and another 150pts more, re-tagging questions. - The usual way to achieve this would be: contribute like crazy...)

(15 Dec '11, 07:52) fbahr ♦

If x is a parameter: floor(x).

If x is a continuous variable, let me point you to: http://yetanothermathprogrammingconsultant.blogspot.com/2009/02/floor-in-minlp-model.html#comment-form

Make sure your specify finite bounds for your integer variable.

As you can see, the floor function can potentially be very expensive if the range of x is large.


answered 11 Dec '11, 14:33

Gilead's gravatar image

Gilead ♦
accept rate: 15%

Thank you Gilead, I just looked at your blog and let me try it asap!

(12 Dec '11, 00:14) Pavan

That is not my blog but the blog of Erwin Kalvelagen. You should bookmark it for future reference.

(12 Dec '11, 00:16) Gilead ♦

Ok... Thanks for the heads-up!

(12 Dec '11, 00:18) Pavan

A blog post on the subject :

Erwin Kalvelagen's blog


answered 15 Dec '11, 18:00

Bo%20Jensen's gravatar image

Bo Jensen ♦
accept rate: 14%

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Asked: 11 Dec '11, 11:29

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