[SCIP] Questions about branch-price-cut

[Oliver Zier]

Hi SCIPers,
I am implementing branch-price-cut using SCIP and I ran into several
problems:
1. For subproblems, I do not free the problem after solving but only free
the transformed problem (sing SCIPfreeTransform). After branching I will
add constraints into subscip to enforce the branching deicison in the
subproblem using SCIPaddCons as I read from several other threads in the
mailing list. However, it seems like the new constraint in subproblem is
not enforced and not active in the subscip. There is no error returned
from SCIPaddCons but it just didn't do what is expected. What am I missing
here?

2. For one of the subproblem, I got a solution like this:
objective value:                                 -2.8
x_Act_10_Eve_7                             1 	(obj:0)
y_Act_10_Eve_8                              1 	(obj:0)
x_Act_10_Eve_8                             1 	(obj:0)
y_Act_10_Eve_9                              1 	(obj:0)
x_Act_10_Eve_9                             1 	(obj:0)
y_Act_10_Eve_10                             1 	(obj:0)
x_Act_10_Eve_10                            1 	(obj:0)
OneCol_10                                           1 	(obj:-2.)
q_1_Act_10_Eve_7                  	13.9285714285714 	(obj:-0)
e_Act_10_Eve_7               	41.7857142857143 	(obj:-0)
So basically I can increase / decrease q and e to certain extent and get
another solution with the same objective value. The constraints for q  and
e are: q >= 1, 42 * q >= 4*e and 42 * q <= 14*e so I would say there are
infinitely many solutions with the same objective but somehow scip only
returns me this solution (using SCIPgetSols). Is there any criteria that
SCIP uses internally to choose which solution to return?

3. I am using reoptimization for subproblems and get here the error:
scipoptsuite-6.0.2/scip/src/scip/presol_symmetry.c:778:
computeSymmetryGroup: Assertion `nhandleconss <= nactiveconss' failed.
The problem seems to be, that in a previous call to SCIPfreeReoptSolve the
number of active constraint in scip->stat is set to zero but not
nactiveconss of the constraint handlers. Here is a backtrace:

#0  0x00007ffff3b2e0d1 in raise () from /lib64/libc.so.6
#1  0x00007ffff3b1755d in abort () from /lib64/libc.so.6
#2  0x00007ffff3b17431 in __assert_fail_base.cold () from /lib64/libc.so.6
#3  0x00007ffff3b26592 in __assert_fail () from /lib64/libc.so.6
#4  0x00007ffff4ea0000 in computeSymmetryGroup
   at scip/src/scip/presol_symmetry.c:778
#5  0x00007ffff4ea3c7b in determineSymmetry
   at scip/src/scip/presol_symmetry.c:1502
#6  0x00007ffff4ea4eac in SCIPgetGeneratorsSymmetry
   at scip/src/scip/presol_symmetry.c:1811
#7  0x00007ffff4ec410e in getSymmetries
   at /scip/src/scip/prop_orbitalfixing.c:184
#8  0x00007ffff4ec4d49 in propagateOrbitalFixing
   at /scip/src/scip/prop_orbitalfixing.c:470
#9  0x00007ffff4ec60e8 in propExecOrbitalfixing
   at scip/src/scip/prop_orbitalfixing.c:821
#10 0x00007ffff524d5c9 in SCIPpropExec at scip/src/scip/prop.c:674
#11 0x00007ffff5342554 in propagationRound at scip/src/scip/solve.c:531
#12 0x00007ffff5342898 in propagateDomains
   at scip/src/scip/solve.c:609
#13 0x00007ffff534e603 in propAndSolve
   at scip/solve.c:3761

#14 0x00007ffff535004f in solveNode
   at scip/src/scip/solve.c:4190
#15 0x00007ffff535384d in SCIPsolveCIP
   at scip/src/scip/solve.c:4974
#16 0x00007ffff52e15bd in SCIPsolve  at scip/src/scip/scip_solve.c:2652
#17 0x000000000074a456 in ObjPricerRCPSP::scip_redcost(Scip*,
SCIP_Pricer*, double*, unsigned int*, SCIP_Result*) ()
#18 0x00007ffff53d2df1 in pricerRedcostObj at
scip/src/objscip/objpricer.cpp:182
#19 0x00007ffff523d801 in SCIPpricerRedcost  at scip/src/scip/pricer.c:410
#20 0x00007ffff523dbb4 in SCIPpricerExec
   at scip/src/scip/pricer.c:494
#21 0x00007ffff5347c44 in SCIPpriceLoop
   at scip/src/scip/solve.c:2121
#22 0x00007ffff5348f0c in priceAndCutLoop  at scip/src/scip/solve.c:2382
#23 0x00007ffff534c049 in solveNodeLP
   at scip/src/scip/solve.c:3086
#24 0x00007ffff534ef60 in propAndSolve
   at scip/src/scip/solve.c:3890
#25 0x00007ffff535004f in solveNode
   at scip/src/scip/solve.c:4190
#26 0x00007ffff535384d in SCIPsolveCIP
   at scip/src/scip/solve.c:4974
#27 0x00007ffff52e15bd in SCIPsolve  at scip/src/scip/scip_solve.c:2652
#28 0x00000000006f4cdf in RCPSP::solve(int) ()
#29 0x00000000007aa9e6 in main ()


Best,
Oliver