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10 best solutions with the MIP solution enumerator

Description
We take the power generation problem stored in hpw15.mps which seeks to optimise the operating pattern of a group of electricity generators. We run the MIP solution enumerator on the problem using the default setup obtaining the best 10 solutions. The best 10 solutions are stored to a MIP solution pool. The solutions' objectives and solution values are printed to screen.

Source Files
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Data Files

MipSolEnum.cs

/***********************************************************************
Xpress Optimizer Examples
=========================

file MipSolEnum.cs

Find the 10 best solutions with the MIP solution enumerator

We take the power generation problem stored in hpw15.mps which seeks to
optimise the operating pattern of a group of electricity generators. We
run the MIP solution enumerator on the problem using the default setup
obtaining the best 10 solutions. The best 10 solutions are stored to a
MIP solution pool.  The solutions' objectives and solution values are
printed to screen.

(c) 2008,2021 Fair Isaac Corporation
***********************************************************************/

using System;
using System.IO;
using Optimizer;

namespace XPRSExamples
{
class MipSolEnum
{
static void Main(string[] args)
{
XPRS.Init();

XPRSprob prob = new XPRSprob();

XPRSmipsolpool msp = new XPRSmipsolpool();
XPRSmipsolenum mse = new XPRSmipsolenum();

prob.MPSFormat = -1;
int nCols = prob.Cols;

/* Avoid duplicated solutions from heuristics. */
msp.DuplicateSolutionsPolicy = 3;

/* Disable dual reductions to prevent dominated solutions from */
/* being presolved away. */
prob.MIPDualReductions = 2;

/* Run the enumeration */
int nMaxSols = 10;
mse.Minim(prob, msp, XPRSdefaultMipSolEnumHandler.GetDefaultHandlerCallback(), null, ref nMaxSols);

/* Print out the solutions found */
int nSols = mse.Solutions;
for (int i = 1; i <= nSols; i++)
{
int[] iSolutionId = new int[1];
double dObj;
int nSols2, nReturnedSolIds, solutionIdStatus;
mse.GetSolList((int)XPRSattribute.Mse_Metric_MipObject, i, i, iSolutionId, out nReturnedSolIds, out nSols2);
mse.GetSolMetric(iSolutionId[0], out solutionIdStatus, (int)XPRSattribute.Mse_Metric_MipObject, out dObj);
Console.WriteLine("--------\n" + i + " = " + dObj);
for (int j = 0; j < nCols; j++)
{
double[] dSol = new double[1];
int nValuesReturned;
msp.GetSol(iSolutionId[0], out solutionIdStatus, dSol, j, j, out nValuesReturned);
Console.WriteLine(j + " = " + dSol[0]);
}
}

XPRS.Free();
}
}
}