[Scip] SCIP-2.1.1 and SCIP-3.0.1 give different optimal values

[Masahiro Sakai]

Thank you all,

Finally Michael Winkler sent me a fix that fixes the bug of SCIP-3.0.1,
and SCIP-3.0.1 with this fix finds the 2205487 solution.

I also verified feasibility of the 2205487 solution using exact arithmetic.

Best regards,

Masahiro

2013/6/3 Tobias Achterberg <achterberg at zib.de>:
> Yes, this should be a bug somewhere in SCIP.
>
> CPLEX finds the 2205487 solution, this solution looks almost perfectly
> feasible, and the MIP kappa statistics show a 100% stable bases:
>
> MIP - Integer optimal solution:  Objective =  2.2054870000e+06
> Solution time =    0.63 sec.  Iterations = 371  Nodes = 0
> Deterministic time = 553.33 ticks  (876.25 ticks/sec)
>
> CPLEX> disp sol qual
> Incumbent solution:
> MILP objective                                 2.2054870000e+06
> MILP solution norm |x| (Total, Max)            4.03400e+03  1.00000e+00
> MILP solution error (Ax=b) (Total, Max)        0.00000e+00  0.00000e+00
> MILP x bound error (Total, Max)                0.00000e+00  0.00000e+00
> MILP x integrality error (Total, Max)          9.99201e-16  1.11022e-16
> MILP slack bound error (Total, Max)            3.33067e-16  1.11022e-16
>
> Branch-and-cut subproblem optimization:
> Max condition number:                    2.6097e+01
> Percentage (number) of stable bases:     100.00%   (20)
> Percentage (number) of suspicious bases:   0.00%   (0)
> Percentage (number) of unstable bases:     0.00%   (0)
> Percentage (number) of ill-posed bases:    0.00%   (0)
>
>
> Regards,
>
> Tobias
>
>
>
> On 05/31/13 17:06, Victor Miller wrote:
>>
>> This looks like it might be a bug in presolve.  As a guess I set
>> maxrounds to 3 in 3.0.1 and then it found the right optimal solution.
>>
>> Victor
>>
>>
>> On Fri, May 31, 2013 at 10:39 AM, Masahiro Sakai
>> <masahiro.sakai at gmail.com <mailto:masahiro.sakai at gmail.com>> wrote:
>> Hi,
>>
>> I solved a minimization MILP problem attached as rand717_l2.wcnf.lp.gz
>> using SCIP-2.1.1 and SCIP-3.0.1, but they delivered differenct results:
>>
>> * SCIP-2.1.1 returned 2205487 as the optimal value, while
>> * SCIP-3.0.1 returned 2223207 as the optimal value.
>>
>> I'm wondering whether it is a bug of SCIP-3.0.1 or just a numerical
>> problem.
>>
>> The problem rand717_l2.wcnf.lp is converted from a weighted partial
>> Max-SAT problem rand717_l2.wcnf.gz. And I used SCIP binaries
>> downloaded from the SCIP website: scip-2.1.1.linux.x86_64.gnu.opt.spx.zip
>> and scip-3.0.1.linux.x86_64.gnu.opt.spx.zip.
>>
>> Thanks in advance,
>>
>> Masahiro
>>
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>>
>>
>> On Fri, May 31, 2013 at 10:39 AM, Masahiro Sakai
>> <masahiro.sakai at gmail.com <mailto:masahiro.sakai at gmail.com>> wrote:
>>
>>     Hi,
>>
>>     I solved a minimization MILP problem attached as rand717_l2.wcnf.lp.gz
>>     using SCIP-2.1.1 and SCIP-3.0.1, but they delivered differenct
>> results:
>>
>>     * SCIP-2.1.1 returned 2205487 as the optimal value, while
>>     * SCIP-3.0.1 returned 2223207 as the optimal value.
>>
>>     I'm wondering whether it is a bug of SCIP-3.0.1 or just a numerical
>>     problem.
>>
>>     The problem rand717_l2.wcnf.lp is converted from a weighted partial
>>     Max-SAT problem rand717_l2.wcnf.gz. And I used SCIP binaries
>>     downloaded from the SCIP website:
>>     scip-2.1.1.linux.x86_64.gnu.opt.spx.zip
>>     and scip-3.0.1.linux.x86_64.gnu.opt.spx.zip.
>>
>>     Thanks in advance,
>>
>>     Masahiro
>>
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>>     http://listserv.zib.de/mailman/listinfo/scip
>>
>>
>>
>>
>>
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