[Symphony] Dramatic performance drop since 5.1.10

[Pierre.Lebodic at lri.fr]

Hello,

I've been using the C callbacks of Symphony 5.1.10 for a while and I
recently tried updating to 5.2. On a batch of 80 test instances, I
measured the run time of the updated solver. "Sys time" went from 2sec
with 5.1 to 2m55sec with 5.2. As a comparison, cbc 2.3 takes 23sec. A
little digging made me try with feasibility pump disabled, which roughly
cut the sys time in two, but it's still nowhere close the previous
version. I'd like to know if there are parameters that can be changed to
get closer to how fast Symphony 5.1 performs. I'm solving 0-1 problems. I
can provide MPS files if needed.

The reason why I'm willing to switch to 5.2 is that I'm experiencing what
seems to be a bug: when TM_gap_limit != -1, feasible solutions that don't
respect the gap limit are produced. As far as I've been able to see, this
bug seems to be fixed in 5.2. If you know about this bug, a quick edit in
my 5.1 source would also do the trick.
Thanks in advance

Pierre Le Bodic