Re: [Help-glpk] does anyone use yoyo's GLPKSharp?

[bo liu]

yoyovicks,

 

i'm so happy that i can receive your reply. this is the example of GLPK.pdf  named sample.c    .

maximize
z = 10x1 + 6x2 + 4x3
subject to
x1 + x2 + x3 <= 100
10x1 + 4x2 + 5x3 <= 600
2x1 + 2x2 + 6x3 <= 300
where all variables are non-negative
x1>= 0, x2>=0, x3>=0

this is a simple LP problem , and i want to use your GLPKSharp.dll to solve some problem like this (because i use C# and VS2005 too),so i translate it into your GLPKSharp form to study how to use your GLPKSharp.dll  .

 

 

in this example ,the coefficients matrix of structural variables are prepared like this:

 

s21:  ia[1] = 1, ja[1] = 1, ar[1] =  1.0;   /* a[1,1] =  1 */
s22:  ia[2] = 1, ja[2] = 2, ar[2] =  1.0;   /* a[1,2] =  1 */
s23:  ia[3] = 1, ja[3] = 3, ar[3] =  1.0;   /* a[1,3] =  1 */
s24:  ia[4] = 2, ja[4] = 1, ar[4] = 10.0;   /* a[2,1] = 10 */
s25:  ia[5] = 3, ja[5] = 1, ar[5] =  2.0;   /* a[3,1] =  2 */
s26:  ia[6] = 2, ja[6] = 2, ar[6] =  4.0;   /* a[2,2] =  4 */
s27:  ia[7] = 3, ja[7] = 2, ar[7] =  2.0;   /* a[3,2] =  2 */
s28:  ia[8] = 2, ja[8] = 3, ar[8] =  5.0;   /* a[2,3] =  5 */
s29:  ia[9] = 3, ja[9] = 3, ar[9] =  6.0;   /* a[3,3] =  6 */
s30:  glp_load_matrix(lp, 9, ia, ja, ar);

 

 if i use theGLPKSharp.dll , i can't accomplish it like this.

 

 

but finally i achieve it by this form:

        int[] a = new int[] { 0, 1, 2, 3 };

        p.SetMatRow(1, a, new double[] { 0, 1.0, 1.0, 1.0 });
        p.SetMatRow(2, a, new double[] { 0, 10.0, 4.0, 5.0 });
        p.SetMatRow(3, a, new double[] { 0, 2.0, 2.0, 6.0 });

 

i think the array a[] must be the array of column index,right?but in this array the first value is 0. i also know that GLPK need the array starts from a[1] instead of a[0] ,but in the C# array starts from a[0].Is this why the first value of array a[] is 0?  i only add 3 columns p.AddCols(3)  .  but it works.  i want to know that if this method works in other LP problem.

could it be that the GLPK read the array a[] from a[1]? the a[0] is left out.

and the new double[] { 0, 1.0, 1.0, 1.0 } are also the same as a[]?

 

 

but i still don't know how to use the p.LoadMatrix through your GLPKSharp.dll  .

 

 

the follow is the your API form translate from sample.c (i made it ,and it works.this is my first time using GLPK through API and i use it in the WebForm)

 

using System;
using System.Data;
using System.Configuration;
using System.Collections;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using GlpkSharp;

 protected void Page_Load(object sender, EventArgs e)
    {
                double z, x1, x2, x3;
                LPProblem p = new LPProblem();
        p.Name = "LEO";
        p.ObjectiveName = "test";
        p.ObjectiveDirection = OptimisationDirection.MAXIMISE;

        p.AddRows(3);
        p.SetRowName(1, "p");
        p.SetRowBounds(1, BOUNDSTYPE.Upper, 0.0, 100.0);
        p.SetRowName(2, "q");
        p.SetRowBounds(2, BOUNDSTYPE.Upper, 0.0, 600.0);
        p.SetRowName(3, "r");
        p.SetRowBounds(3, BOUNDSTYPE.Upper, 0.0, 300.0);

        p.AddCols(3);
        p.SetColName(1, "x1");
        p.SetColBounds(1, BOUNDSTYPE.Lower, 0.0, 0.0);
        p.SetObjCoef(1, 10.0);
        p.SetColName(2, "x2");
        p.SetColBounds(2, BOUNDSTYPE.Lower, 0.0, 0.0);
        p.SetObjCoef(2, 6.0);
        p.SetColName(3, "x3");
        p.SetColBounds(3, BOUNDSTYPE.Lower, 0.0, 0.0);
        p.SetObjCoef(3, 4.0);

 

        int[] a = new int[] { 0, 1, 2, 3 };

        p.SetMatRow(1, a, new double[] { 0, 1.0, 1.0, 1.0 });
        p.SetMatRow(2, a, new double[] { 0, 10.0, 4.0, 5.0 });
        p.SetMatRow(3, a, new double[] { 0, 2.0, 2.0, 6.0 });

               

        try
        {

            p.SolveSimplex();
            p.WriteSol("c:\\test1.txt");
            z = p.GetObjectiveValue();
            x1 = p.GetColPrimal(1);
            x2 = p.GetColPrimal(2);
            x3 = p.GetColPrimal(3);
            Response.Write(z + "<br>");
            Response.Write(x1 + "<br>");
            Response.Write(x2 + "<br>");
            Response.Write(x3 + "<br>");
            }
        catch (Exception ex)
        {
            Response.Write(ex.Message);
        }