[Symphony] help with interpreting the output (does symphony continue after finding optimal solution?)

[Iulian Ober]

Hello, 

I'm trying to use Symphony (5.2.4) off-the-shelf (no custom code) to solve a large ILP problem (a 0/1 problem actually).
For this problem I know that all feasible solutions have value = 81, like the LP optimal solution.
The output seems to indicate that the solver continues to search long after finding an optimal solution, but maybe I'm misinterpreting it. Here is a condensed version of what I get:

=================================================
Starting Preprocessing...
Preprocessing finished...
         coefficients modified: 47022
         constraints removed: 7116
         variables fixed: 1844
Problem has 
         33846 constraints 
         8560 variables 
         403100 nonzero coefficients

Total Presolve Time: 0.689973...

Solving...

solving root lp relaxation
done: 0 left: 1 ub: ?? lb: ?? time: 20
done: 0 left: 1 ub: ?? lb: ?? time: 40
...
...
done: 0 left: 1 ub: ?? lb: ?? time: 1524
The LP value is: 81.000 [0,54820]					-- found the continuous solution ?
...
...
done: 0 left: 1 ub: ?? lb: ?? time: 10979
done: 1 left: 2 ub: ?? lb: 81.00 time: 10999			-- does this mean it found a feasible integer solution for 81 ?
...
...
done: 6 left: 7 ub: ?? lb: 81.00 time: 14783
done: 17 left: 12 ub: 81.00 lb: 81.00 gap: 0.00 time: 22276	-- is this because no direction for the optimization is specified in the MPS model, so it tries both?
...
...
done: 28 left: 1 ub: 81.00 lb: 81.00 gap: 0.00 time: 74648

****************************************************
* Optimal Solution Found                           *
* Now displaying stats and best solution found...  *
****************************************************
...
...
=======================================================

Can anybody please help me interpret the output ?
I tried to augment verbosity (verbosity 3), but then I get fewer output (!?) -- no periodic messages every 20 sec anymore...

I also tried to set :
	find_first_feasible 1
but does not seem to finish quicker, so maybe I'm wrong...

Thanks for your help,

Iulian Ober 
IRIT, Universite de Toulouse
118 route de Narbonne 
31062 Toulouse, France
http://www.irit.fr/~Iulian.Ober/