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

Fri May 8 07:21:52 EDT 2015

Hi James,

I edited the your lp problem, just exactly John posted.

i.e.

p0_2 + p1_2 - x2 = 0
p0_3 + p1_3 - x3 = 0

before solving it.

Noli

On 5/8/15, James.Gunning at csiro.au <James.Gunning at csiro.au> wrote:
> Hi Noli,
>        Thanks for the suggestion, but, my brand new build of trunk yields
> .....
> Welcome to the CBC MILP Solver
> Version: Trunk (unstable)
> Build Date: May  8 2015
> Revision Number: 2189
>
> command line - ********Cbc/build/bin/cbc lp_solve_in.lp solve solu stdout
> (default strategy 1)
> Continuous objective value is 6.00724 - 0.00 seconds
> Cgl0002I 4 variables fixed
> Cgl0000I Cut generators found to be infeasible! (or unbounded)
> Pre-processing says infeasible or unbounded
> Integer infeasible - objective value 6.00724000
>       0 p1_3                   0                       0
>       1 x1                   0.5                       0
>       2 x3                   0.5                       0
>       3 x0                   0.5                       0
>       4 p0_2                   0                       0
>       5 x2                   0.5                       0
>       6 p0_3                   0                 1.60004
>       7 p1_2                   0                 6.00724
>
> So I'm still mystified!
>
> Best wishes,
>        James.
>
> James Gunning
> CSIRO
> Clayton, Vic., Australia
> ________________________________________
> From: Noli Sicad [nsicad at gmail.com]
> Sent: Friday, 8 May 2015 7:13 PM
> To: Gunning, James (Energy, Clayton North)
> Cc: cbc at list.coin-or.org
> Subject: Re: [Cbc] "Integer infeasible..." issue?
>
> 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.
>>
>>
>>
>>
>