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

[Jens Schuchhardt]

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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