[Symphony] Only Branch and Bound posible and lower Bound in Symphony

[Ted Ralphs]

Can you send me the file? I'm not sure what the problem with tailoff
is precisely. We don't usually use SYMPHONY in pure branch and bound
mode, so there may be a problem. As for the bounds, SYMPHONY should
print log message with both upper and lower bound indicated
periodically and should also print that information at termination. If
you are not seeing that, perhaps it is related to the problem you're
having.

Cheers,

Ted

On Tue, Feb 8, 2011 at 11:33 AM, Jens Schuchhardt <troepfchen at web.de> wrote:
> hello,
>
> I have got 2 questions about Symphony, I am working with the precompiled binaries:
>
> 1) I would like to point out the differences between "branch and bound" and "branch and cut". To do so I would like to solve a GAP with 10 jobs and 5 machines (from Wolsey 1998). Symphony should solve this with the following parameters
>
> verbosity 1   # Gesprächigkeit
> prep_level -1  # -1 = kein Preprocessing
> fp_enabled -1 # Feasibility pump Heuristik deaktivieren
> strong_branching_cand_num_max 0
> strong_branching_cand_num_min 0
> strong_branching_red_ratio 8
> should_use_rel_br -1   # Strong Branching aus
> rel_br_override_default -1
> rel_br_threshold -1
> rel_br_max_solves -1
> rel_br_threshold -1
> generate_cgl_gomory_cuts -1
> generate_cgl_knapsack_cuts -1
> generate_cgl_oddhole_cuts -1
> generate_cgl_probing_cuts -1
> generate_cgl_clique_cuts -1
> generate_cgl_flow_and_cover_cuts -1
> generate_cgl_rounding_cuts -1
> generate_cgl_lift_and_project_cuts -1
> generate_cgl_twomir_cuts -1
>
> in branch and bound. But Symphony can't solve the example because producing a "tail off". I have tested a plenty of options, but no diffrence: tail off :-(
> Has anybody an idea, what to do ?
>
> 2)  The Branch and Bound method uses  a lower and a upper bound. The upper bound is handled by the tree manager, but what's about the lower bound ? Doesn't Symphony have got a global lower bound, which is increasing during the algorithm works?
>
>
>
> Thanks for any hint !
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-- 
Dr. Ted Ralphs
Associate Professor, Lehigh University
(610) 628-1280
ted 'at' lehigh 'dot' edu
coral.ie.lehigh.edu/~ted