[Couenne] Couenne keeps running outputting the same B&B value

[Pierre-Emmanuel Emeriau]

Hello,

I am having some issue trying to solve my bilinear nonconvex problem (of 
small dimension, attached if needed). I am using couenne interfaced with 
pyomo.
I am expected the optimal value to be around 0.85 but when I launch the 
solver, couenne seems to be blocked at the same line:
```Cbc0010I After 4200 nodes, 1329 on tree, -0.85355341 best solution, 
best possible -1 (15.43 seconds)````.
And it keeps going on as if it cannot terminate the branch&bound 
algorithm. The solution seems good to me but I am wondering why couenne 
does not stop at some point. If I set ```allowable_gap``` to an 
unreasonable value (above 0.15) it will terminated and I assume this is 
because:
```Cbc0011I Exiting as integer gap of 0.14644659 less than 0.15 or 0%```.
But not if I set this flag to a value below 0.14. Maybe it cannot close 
the gap. Could that be the case? Which brings me to my next question: 
can I certify optimality?

Thanks a lot for your help.
Best,
-------------- next part --------------
A non-text attachment was scrubbed...
Name: bilinear_RAC21.py
Type: text/x-python
Size: 3619 bytes
Desc: not available
URL: <http://list.coin-or.org/pipermail/couenne/attachments/20200409/dbae718b/attachment.py>