[Cbc] Gomory or not Gomory, that is the question.

[Yves Touchard]

Hello,

You will find here 
(https://www.dropbox.com/s/ayo93hi4togpc9m/noGom.lp?dl=0) a constraint 
file for which cbc founds a solution when Gomory cuts are removed or for 
specific cutlength values.

In other words, the following command leads to an infeasible problem:
//soft/cbc-trunk-2149/bin/cbc noGom.lp branch printingOptions normal 
solution noGom.sol/

and with the following commands, cbc claims that there is a solution:
//soft/cbc-trunk-2149/bin/cbc noGom.lp gomory off branch printingOptions 
normal solution noGom.sol/
//soft/cbc-trunk-2149/bin/cbc noGom.lp cutlength xx branch 
printingOptions normal solution noGom.sol/ (with xx equal to -1, 0, 10, 
20... and different from 30...)

Since our problems are dynamically generated, it is very painful to try 
to solve them with different options, hoping that the right set is in 
the list.

So, is there a way to find this set of options.
Or could you explain what are the rows that are difficult for cbc.
And, does the change of the continuous variables into integer variables 
help? (for our problems, it makes sense).

Thanks and regards

Yves
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