[SCIP] Scip stops reporting

[Marco Correia]

Hi,

I'm running a problem where at some point SCIP seems to hang, or at least,
it stops logging. This is the output I get from it until that happens:

feasible solution found by trivial heuristic after 0.0 seconds, objective
value 0.000000e+00
presolving:
(round 1, fast)       6 del vars, 9 del conss, 0 add conss, 96 chg bounds,
0 chg sides, 0 chg coeffs, 0 upgd conss, 86 impls, 148 clqs
(round 2, exhaustive) 6 del vars, 92 del conss, 0 add conss, 96 chg bounds,
83 chg sides, 1 chg coeffs, 0 upgd conss, 86 impls, 148 clqs
(round 3, exhaustive) 6 del vars, 92 del conss, 0 add conss, 96 chg bounds,
83 chg sides, 1 chg coeffs, 539 upgd conss, 86 impls, 148 clqs
  (0.0s) probing cycle finished: starting next cycle
(round 4, exhaustive) 6 del vars, 92 del conss, 0 add conss, 177 chg
bounds, 83 chg sides, 1 chg coeffs, 539 upgd conss, 1028 impls, 247 clqs
(round 5, fast)       6 del vars, 92 del conss, 0 add conss, 177 chg
bounds, 83 chg sides, 27 chg coeffs, 539 upgd conss, 1028 impls, 247 clqs
  (0.0s) probing: 108/148 (73.0%) - 0 fixings, 0 aggregations, 975
implications, 82 bound changes
  (0.0s) probing aborted: 50/50 successive totally useless probings
  (0.0s) symmetry computation started: requiring (bin +, int -, cont +),
(fixed: bin -, int +, cont -)
  (0.0s) no symmetry present
presolving (6 rounds: 6 fast, 4 medium, 4 exhaustive):
6 deleted vars, 92 deleted constraints, 0 added constraints, 178 tightened
bounds, 0 added holes, 83 changed sides, 27 changed coefficients
1068 implications, 247 cliques
presolved problem has 421 variables (148 bin, 0 int, 0 impl, 273 cont) and
837 constraints
   193 constraints of type <varbound>
   148 constraints of type <setppc>
   298 constraints of type <linear>
   198 constraints of type <logicor>
Presolving Time: 0.02
transformed 1/1 original solutions to the transformed problem space

time | node  | left  |LP iter|LP it/n|mem/heur|mdpt |vars |cons |rows |cuts
|sepa|confs|strbr|  dualbound   | primalbound  |  gap   | compl.
 0.0s|     1 |     0 |   398 |     - |  6511k |   0 | 421 | 851 | 836 |   0
|  0 |  13 |   0 | 7.631347e-02 | 0.000000e+00 |    Inf | unknown
 0.0s|     1 |     0 |   398 |     - |  6521k |   0 | 421 | 851 | 836 |   0
|  0 |  13 |   0 | 7.631347e-02 | 0.000000e+00 |    Inf | unknown
 0.0s|     1 |     0 |   399 |     - |  6637k |   0 | 421 | 851 | 837 |   1
|  1 |  13 |   0 | 7.466223e-02 | 0.000000e+00 |    Inf | unknown
 0.0s|     1 |     0 |   414 |     - |  6782k |   0 | 421 | 851 | 838 |   2
|  2 |  13 |   0 | 7.388510e-02 | 0.000000e+00 |    Inf | unknown
 0.1s|     1 |     0 |   424 |     - |  6936k |   0 | 421 | 851 | 842 |   6
|  3 |  13 |   0 | 6.982341e-02 | 0.000000e+00 |    Inf | unknown
 0.1s|     1 |     0 |   433 |     - |  7114k |   0 | 421 | 851 | 845 |   9
|  4 |  13 |   0 | 6.814827e-02 | 0.000000e+00 |    Inf | unknown
 0.1s|     1 |     0 |   435 |     - |  7273k |   0 | 421 | 851 | 846 |  10
|  5 |  13 |   0 | 6.814318e-02 | 0.000000e+00 |    Inf | unknown
 0.1s|     1 |     0 |   442 |     - |  7418k |   0 | 421 | 851 | 847 |  11
|  6 |  13 |   0 | 6.780902e-02 | 0.000000e+00 |    Inf | unknown
 0.1s|     1 |     0 |   449 |     - |  7686k |   0 | 421 | 851 | 851 |  15
|  7 |  13 |   0 | 6.745065e-02 | 0.000000e+00 |    Inf | unknown
 0.1s|     1 |     0 |   477 |     - |  7902k |   0 | 421 | 851 | 853 |  17
|  8 |  13 |   0 | 6.700544e-02 | 0.000000e+00 |    Inf | unknown
 0.2s|     1 |     0 |   485 |     - |  8009k |   0 | 421 | 852 | 855 |  19
|  9 |  14 |   0 | 6.606474e-02 | 0.000000e+00 |    Inf | unknown
 0.2s|     1 |     0 |   501 |     - |  8476k |   0 | 421 | 852 | 857 |  21
| 10 |  14 |   0 | 6.543249e-02 | 0.000000e+00 |    Inf | unknown
 0.2s|     1 |     0 |   561 |     - |  8569k |   0 | 421 | 852 | 859 |  23
| 11 |  14 |   0 | 6.433780e-02 | 0.000000e+00 |    Inf | unknown
 0.2s|     1 |     0 |   584 |     - |  8751k |   0 | 421 | 853 | 860 |  24
| 12 |  15 |   0 | 6.388945e-02 | 0.000000e+00 |    Inf | unknown
 0.2s|     1 |     0 |   585 |     - |  8845k |   0 | 421 | 854 | 861 |  25
| 13 |  16 |   0 | 6.388368e-02 | 0.000000e+00 |    Inf | unknown
time | node  | left  |LP iter|LP it/n|mem/heur|mdpt |vars |cons |rows |cuts
|sepa|confs|strbr|  dualbound   | primalbound  |  gap   | compl.
 0.2s|     1 |     0 |   600 |     - |  9406k |   0 | 421 | 854 | 862 |  26
| 14 |  16 |   0 | 6.351136e-02 | 0.000000e+00 |    Inf | unknown
 0.3s|     1 |     0 |   605 |     - |  9499k |   0 | 421 | 854 | 862 |  27
| 15 |  16 |   0 | 6.347853e-02 | 0.000000e+00 |    Inf | unknown
 0.3s|     1 |     0 |   611 |     - |  9499k |   0 | 421 | 854 | 865 |  30
| 16 |  16 |   0 | 6.329991e-02 | 0.000000e+00 |    Inf | unknown
 0.4s|     1 |     2 |  1077 |     - |  9614k |   0 | 421 | 854 | 865 |  30
| 18 |  16 |  26 | 6.258119e-02 | 0.000000e+00 |    Inf | unknown

I've run it with a debugger, but given it is compiled without debugging
symbols, I can only see that it is somewhere inside SCIPsolve.

I can dig deeper, but would first like to ask if this behaviour could be
normal.

Thanks
Marco
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