[Coin-discuss] Strange termination

[Alan King]

Probably this condition is due to an unbounded ray being detected but no 
feasible solution has yet been found? 

isAbandoned() might be the most appropriate test in that case.

Sounds like an interesting problem -- might be nice to have in the samples 
or for a regression test.

Alan King



Matthew Saltzman <mjs at ces.clemson.edu> 
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06/17/2005 01:08 PM
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Re: [Coin-discuss] Strange termination






On Fri, 17 Jun 2005, Kasper Bonne Rasmussen wrote:

>
> On Fri, 17 Jun 2005, Matthew Saltzman wrote:
>> On Fri, 17 Jun 2005, Kasper Bonne Rasmussen wrote:
>>> CPXgetstat(env_, getMutableLpPtr()) returns 119 in the call that fails 
to
>>> generate an optimal solution. cplex.h defines 119 as
>>> CPXMIP_NODE_FILE_LIM_INFEAS. None of the query methods check for that.
>>
>> What version of CPLEX are we talking about here?
>>
>> Since at least CPLEX 8.1, code 119 is CPX_MIP_INForUNBD.
>
> Cplex version 9.0 and you are absolutely right. I was looking in a
> cplex-headerfile v7.0, sorry.
>
> ..but there is still no query method that checks for this, as far as I 
can
> see.

I'm not terribly surprised.  But which of these should detect it?

   isAbandoned()
   isProvenOptimal()
   isProvenPrimalInfeasible()
   isProvenDualInfeasible()
   isPrimalObjectiveLimitReached()
   isDualObjectiveLimitReached()
   isIterationLimitReached()

The docs are not clear what the circumstances are that lead to this return 

code.  There is a CPXMIP_UNBOUNDED (unbdd ray found) and a CPXMIP_INFEAS 
(proven infeasible).  So I will guess that CPXMIP_INForUNBD must arise in 
some ambiguous case.  We'd need to get CPLEX to weigh in on whether the 
two cases are distinguishable with some additional calls.

> /Kasper

-- 
                                 Matthew Saltzman

Clemson University Math Sciences
mjs AT clemson DOT edu
http://www.math.clemson.edu/~mjs
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