[Coin-lpsolver] What is the best way of getting out N feasible extreme points?

[Yiming Yao]

John,

Thanks for your correction. I used 
"model_->nonLinearCost()->numberInfeasibilities()==0" as feasibility check; 
however I couldn't get any feasible extreme point (FEP) for a test LP of 
size 57var x 145 constrs. This LP was solved to optimality. There must be 
at least one FEP (there should a lot more) for the code to get by trapping 
message 102 (CLP_SIMPLEX_HOUSE2) , which is generated every simplex iteration.

My intention is to get every FEP during a simplex process (Steps are 
described below.)

Any suggestions?

Thanks,

Yiming

--------------------------------------------------------
Here's what I've done:

1. in ClpMessage.cpp, changed
{CLP_SIMPLEX_HOUSE2,102,4,"%d %g In: %c%d Out: %c%d%? dj ratio %g distance 
%g%? dj %g distance %g"},
to
{CLP_SIMPLEX_HOUSE2,102,1,"%d %g In: %c%d Out: %c%d%? dj ratio %g distance 
%g%? dj %g distance %g"},

2. Created MlpMessageHandler class by inheriting CoinMessageHandler in a 
similar way as the MyMessageHandler class.  The main method of this class 
looks like the following (I also asked some questions as comments):

int
MlpMessageHandler::print()
{
   if (currentSource()=="Clp") {
     if (currentMessage().externalNumber()==102) {
      // feasible?
       if (model_->nonLinearCost()->numberInfeasibilities()==0) {

         //compute objective value based on John Forrest's code
         double objValue = computeObjValue(model_);

         // Is the objective value within limit?
         if( objValue > 0 && objValue <= artificialBound) { // 
artificialBound is an input parameter
         //twoLevelPtr points to my algorithm object.
           twoLevelPtr->addCut(solution);

         }
       }
     }
   }
   return CoinMessageHandler::print();
}

----------------------------


At 03:35 AM 8/7/2003 -0400, John J Forrest wrote:




>One problem may be that I got it all wrong and the test for feasibility is
>not correct.  The correct test is
>
>model_->nonLinearCost()->numberInfeasibilites()==0
>
>with ClpNonLinearCost.hpp included.
>
>I will get round to tidying up code some time but hopefully that will work
>for now.
>
>John Forrest