[Cbc] "Integer infeasible..." issue?

[Noli Sicad]

Hi James,

It can be solved using the trunk, see the logs (below).

Noli

~~~~

Running tool: CBC CPLEX LP MIP

Welcome to the CBC MILP Solver
Version: Trunk (unstable)
Build Date: Apr 18 2015
Revision Number: 2180

command line - /usr/local/bin/cbc cbc_lp.lp -printi csv -solve -solu
solution_cplex_.csv (default strategy 1)
Option for printingOptions changed from normal to csv
Continuous objective value is -3.30662 - 0.00 seconds
Cgl0003I 0 fixed, 0 tightened bounds, 8 strengthened rows, 0 substitutions
Cgl0003I 0 fixed, 0 tightened bounds, 4 strengthened rows, 0 substitutions
Cgl0004I processed model has 10 rows, 6 columns (6 integer (6 of which
binary)) and 34 elements
Cbc0038I Initial state - 0 integers unsatisfied sum - 0
Cbc0038I Solution found of -3.30662
Cbc0038I Before mini branch and bound, 6 integers at bound fixed and 0
continuous
Cbc0038I Mini branch and bound did not improve solution (0.00 seconds)
Cbc0038I After 0.00 seconds - Feasibility pump exiting with objective
of -3.30662 - took 0.00 seconds
Cbc0012I Integer solution of -3.30662 found by feasibility pump after
0 iterations and 0 nodes (0.00 seconds)
Cbc0001I Search completed - best objective -3.30662, took 0 iterations
and 0 nodes (0.00 seconds)
Cbc0035I Maximum depth 0, 0 variables fixed on reduced cost
Cuts at root node changed objective from -3.30662 to -3.30662
Probing was tried 0 times and created 0 cuts of which 0 were active
after adding rounds of cuts (0.000 seconds)
Gomory was tried 0 times and created 0 cuts of which 0 were active
after adding rounds of cuts (0.000 seconds)
Knapsack was tried 0 times and created 0 cuts of which 0 were active
after adding rounds of cuts (0.000 seconds)
Clique was tried 0 times and created 0 cuts of which 0 were active
after adding rounds of cuts (0.000 seconds)
MixedIntegerRounding2 was tried 0 times and created 0 cuts of which 0
were active after adding rounds of cuts (0.000 seconds)
FlowCover was tried 0 times and created 0 cuts of which 0 were active
after adding rounds of cuts (0.000 seconds)
TwoMirCuts was tried 0 times and created 0 cuts of which 0 were active
after adding rounds of cuts (0.000 seconds)

Result - Optimal solution found

Objective value:                -3.30662000
Enumerated nodes:               0
Total iterations:               0
Time (CPU seconds):             0.00
Time (Wallclock seconds):       0.00

Total time (CPU seconds):       0.00   (Wallclock seconds):       0.01


real	0m0.018s
user	0m0.010s
sys	0m0.005s

Done.


On 5/8/15, James Gunning <James.Gunning at csiro.au> wrote:
> Hello All,
>         This is probably a dumb question: why does this simple .lp file
>
> Min
> obj: -10.9139 p1_3 +15.3211 x1 -3.30662 x3
> s.t.
> x0 - p0_2 >= 0
> x2 - p0_2 >= 0
> p0_2 - x0 - x2 >= -1
> x0 - p0_3 >= 0
> x3 - p0_3 >= 0
> p0_3 - x0 - x3 >= -1
> x1 - p1_2 >= 0
> x2 - p1_2 >= 0
> p1_2 - x1 - x2 >= -1
> x1 - p1_3 >= 0
> x3 - p1_3 >= 0
> p1_3 - x1 - x3 >= -1
> x0 + x1 = 1
> x2 + x3 = 1
> p0_2 + p1_2 = x2
> p0_3 + p1_3 = x3
> Binaries
> x0 x1 x2 x3 p0_2 p0_3 p1_2 p1_3
> End
>
>
>
> Give me "Integer infeasible..." under cbc?
>
> lp_solve gives me an integer solution
>
> p1_3                            0
> x1                              0
> x3                              1
> x0                              1
> p0_2                            0
> x2                              0
> p0_3                            1
> p1_2                            0
>
>
>
> I'm sure I've done something stupid, but it may be a subtle roundoff thing?
> This is cbc 2.8.12.
>
> Best wishes all & kudos to John for keeping things going so well...
>        James.
>
>
>
>