[Cbc] Convergence problem with miplib2010/30n20b8

[ycollette.nospam at free.fr]

Hello,

I am trying to run somes tests from miplib2010. And I meet some strange behavior.
If I run clp on 30n20b8.mps without specific options, it converges quickly to a solution:

At line 1 NAME           30n20b8                                                                                                                                                                                                             
At line 2 ROWS                                                                                                                                                                                                                               
At line 580 COLUMNS                                                                                                                                                                                                                          
At line 110291 RHS
At line 110322 BOUNDS
At line 128761 ENDATA
Problem 30n20b8 has 576 rows, 18380 columns and 109706 elements
Model was imported from /home/artelys/repository/coin/Cbc/build/Dependencies/.//MIPLIB2000/src/EP_MIPLIB2000/instances/miplib2010/30n20b8.mps.gz in 0.114319 seconds
Presolve 493 (-83) rows, 11093 (-7287) columns and 63118 (-46588) elements
Perturbing problem by 0.001%%of 301.52267 - largest nonzero change 0.00028965583 ( 9.6064362e-05%%) - largest zero change 0.00028962251
0  Obj 0.041886881 Primal inf 253.60538 (88)
78  Obj 0.044696222 Primal inf 359.4158 (159)
142  Obj 0.04542365 Primal inf 105.42604 (119)
214  Obj 0.045885186 Primal inf 83.292978 (114)
298  Obj 0.046155092 Primal inf 32.89186 (74)
380  Obj 0.048508765 Primal inf 87.130897 (64)
464  Obj 0.057466585 Primal inf 99.796642 (62)
548  Obj 0.068410705 Primal inf 276.03475 (64)
632  Obj 0.077664609 Primal inf 167.63095 (63)
716  Obj 0.08533722 Primal inf 123.90711 (47)
800  Obj 0.093453993 Primal inf 94.340415 (35)
884  Obj 1.079625 Primal inf 0.56385768 (23)
950  Obj 1.669254
Optimal - objective value 1.5664076
After Postsolve, objective 1.5664076, infeasibilities - dual 0 (0), primal 0 (0)
Optimal objective 1.566407646 - 950 iterations time 0.112, Presolve 0.03



Now, If I run cbc on this problem, it never stops.
An example of the log I've got:

Cbc0010I After 91600 nodes, 675 on tree, 1e+50 best solution, best possible 202 (1278.41 seconds)
Cbc0010I After 91700 nodes, 626 on tree, 1e+50 best solution, best possible 202 (1279.79 seconds)
Cbc0010I After 91800 nodes, 724 on tree, 1e+50 best solution, best possible 202 (1281.46 seconds)
Cbc0010I After 91900 nodes, 805 on tree, 1e+50 best solution, best possible 202 (1283.06 seconds)
Cbc0010I After 92000 nodes, 709 on tree, 1e+50 best solution, best possible 202 (1284.15 seconds)


I feel the number of best solutions is quite strange: 1e+50 (this number never changes).

I performed these tests on the trunk version of cbc. I will try the same test on an older version of cbc.

Best regards,

YC