[Couenne] COUENNE stop working somtimes

[Pietro Belotti]

Dear Lili,

sorry for the late reply. After a short discussion with the OS people, it 
seems that the problem is related to the precision used to solve the 
problem. If you add the following option in the option file couenne.opt:

allowable_fraction_gap 1e-5

Couenne will stop execution after the gap is below 1e-5, or .001%. That 
instance has some scaling issues and optimization in Couenne seems to go 
on forever due to the very small difference between primal and dual 
bounds, which however is never reduced to zero. You can set that option to 
a smaller or larger number, and clearly that affects the solution you'll 
get and its quality.

Hope this helps.

Pietro


--
Pietro Belotti
Dept. of Mathematical Sciences
Clemson University
email: pbelott at clemson.edu
phone: 864-656-6765
web:   myweb.clemson.edu/~pbelott

On Wed, 30 Mar 2011, lili tan wrote:

> COUENNE stop working, when I tested OS-2.1.1-win32-msvc9, a binary 
> version download from www.coin-or.org/download/binary/OS.When I ran the 
> command “OSSolverService -solver couenne -osil 
> ../data/osilFiles/avion2.osil”, the message “Problem size before 
> reformulation: 49 variables (0 integer), 15 constraints” is displayed on 
> my computer screen, then the execution stop.  I don’t know the wrong 
> reason is resulted from COUENNE itself or from the avion2.osil file 
> reformulation process. Has been this problem solved in current newest 
> stable source code version OS-2.3.0.zip?
> best regard
> lili tan
>
>
>
> 
>
>
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