Objective function is giving a negative value

[lana...@hotmail.com]

I've just started trying AMPL out. Installed the ampl student binary and cbc.

Then, I tried the first problem on the ampl book.

But here's the result:

http://i.imgur.com/Qvq1JPi.png

It should be 192000 instead of -192000

What gives?

[victor.z...@gmail.com]

Looks like a bug in CBC. I've forwarded it to the CBC mailing list: http://list.coin-or.org/pipermail/cbc/2014-September/001501.html

Note that the bug only affects the objective value displayed by CBC, the objective value reported by AMPL is correct:

ampl: print Profit;

192000

HTH,

Victor

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[Marc Hans]

Thanks, looks like there's a fix already.

This made me lost my faith in cbc, though. Such a simple problem (the first one on the ampl book) and it was already buggy on cbc.

Anyway, I really appreciate your help.