[Help-glpk] help! I need a small example to use GLPK java for MIP

[Zong, Yi]

To it may concern,

I want to use GLPK-java to solve a
simple MIP. 

//    Maximize z =  17 * x1 + 12* x2 

 

//    subject to

//     10*x1+7*x2 <= 40

//        x1+  x2 <= 5

//    where,

//    0.0 <= x1  integer

//    0.0 <= x2  integer

//  result: max=68: x1=4, x2=0;  ??

      

 

The code is shown as following. The
problem is how I can get integer solution?

The result I got is:

Problem created

*     0: obj =  0.000000000e+000  infeas = 0.000e+000 (0)

*     2: obj =  6.833333333e+001  infeas = 0.000e+000 (0)

OPTIMAL SOLUTION FOUND

z = 68.33333333333334

x1 = 1.6666666666666676

x2 = 3.3333333333333326

 

%%%%%%%%%%%%%%%%%%source
code%%%%%%%%%%%%%%

import java.io.File;

import java.io.IOException;

 

import org.gnu.glpk.GLPK;

import org.gnu.glpk.GLPKConstants;

import org.gnu.glpk.SWIGTYPE_p_double;

import org.gnu.glpk.SWIGTYPE_p_int;

import org.gnu.glpk.glp_prob;

import org.gnu.glpk.glp_smcp;

//import org.gnu.glpk.glp_intopt;

//import org.gnu.glpk.glp_iocp;

 

publicclassInteger1 {

//    Maximize z =  17 * x1 + 12* x2 

 

//    subject to

//     10*x1+7*x2 <= 40

//        x1+  x2 <= 5

//    where,

//    0.0 <= x1  integer

//    0.0 <= x2  integer

//  result: max=68: x1=4, x2=0;  ??

      

      static

      { 

    

    try

            {

              // try to load Linux library

                  System.loadLibrary( "glpk_java" ); 

            }

            catch (UnsatisfiedLinkErrore)

            {

                  // try to load Windows library

                  System.loadLibrary("glpk_4_39_java"); 

            }

      }

 

      publicstaticvoidmain(String[] arg)

      {

            glp_probmip;

            glp_smcpparm;

            SWIGTYPE_p_intind;

            SWIGTYPE_p_doubleval;

            intret;

      

 

//      Create problem        

            mip = GLPK.glp_create_prob();

            System.out.println("Problem created");

            GLPK.glp_set_prob_name(mip, "myProblem");

 

//      Define columns

            GLPK.glp_add_cols(mip, 2);

            GLPK.glp_set_col_name(mip, 1, "x1");

            GLPK.glp_set_col_kind(mip, 1, GLPKConstants.GLP_IV);

            GLPK.glp_set_col_bnds(mip, 1, GLPKConstants.GLP_LO, 0,0);

            GLPK.glp_set_col_name(mip, 2, "x2");

            GLPK.glp_set_col_kind(mip, 2, GLPKConstants.GLP_IV);

            GLPK.glp_set_col_bnds(mip, 2, GLPKConstants.GLP_LO, 0,0);

            

            

        

//      Create constraints

          GLPK.glp_add_rows(mip, 3);

 

            GLPK.glp_set_row_name(mip, 1, "c1");

            GLPK.glp_set_row_bnds(mip, 1, GLPKConstants.GLP_UP, 0, 40);

            ind = GLPK.new_intArray(3);

            GLPK.intArray_setitem(ind, 1, 1);

            GLPK.intArray_setitem(ind, 2, 2);

            val = GLPK.new_doubleArray(3);

            GLPK.doubleArray_setitem(val, 1, 10);

            GLPK.doubleArray_setitem(val, 2, 7);

            GLPK.glp_set_mat_row(mip, 1, 2, ind, val);

            

//          

            GLPK.glp_set_row_name(mip, 2, "c2");

            GLPK.glp_set_row_bnds(mip, 2, GLPKConstants.GLP_UP, 0, 5);

            ind = GLPK.new_intArray(3);

            GLPK.intArray_setitem(ind, 1, 1);

            GLPK.intArray_setitem(ind, 2, 2);

            val = GLPK.new_doubleArray(3);

            GLPK.doubleArray_setitem(val, 1, 1);

            GLPK.doubleArray_setitem(val, 2, 1);

            GLPK.glp_set_mat_row(mip, 2, 2, ind, val);

            

 

//      Define objective 

            GLPK.glp_set_obj_name(mip, "z");

            GLPK.glp_set_obj_dir(mip, GLPKConstants.GLP_MAX);

      //    GLPK.glp_set_obj_coef(mip,
0, 0);

            GLPK.glp_set_obj_coef(mip, 1, 17);

            GLPK.glp_set_obj_coef(mip, 2, 12);

 

//    solve model

            parm = newglp_smcp();

            GLPK.glp_init_smcp(parm);

            ret = GLPK.glp_simplex(mip, parm);

            

//      Retrieve solution

                if (ret == 0) {

                  

                  write_lp_solution(mip);

            }

            else {

                  System.out.println("The problem could not be solved");

            };

            

            // free memory

            GLPK.glp_delete_prob(mip);

      }     

      

      /**

       *writesimplexsolution

      address@hidden

       */

      staticvoidwrite_lp_solution(glp_probmip)

      {

            inti;

            intn;

            Stringname;

          doubleval;

            //int val;

            name = GLPK.glp_get_obj_name(mip);

            val  = GLPK.glp_get_obj_val(mip);

            //val  = GLPK.glp_mip_obj_val(mip);

            System.out.print(name);

            System.out.print(" = ");

            System.out.println(val);

            n = GLPK.glp_get_num_cols(mip);

            for(i=1; i <= n; i++)

            {

                  name = GLPK.glp_get_col_name(mip, i);

                  val  = GLPK.glp_get_col_prim(mip, i);

                  //val  = GLPK.glp_mip_col_val(mip, i);

                  System.out.print(name);

                  System.out.print(" = ");

                  System.out.println(val);

            }

      }

 

}

 

 

 

   Yi Zong
Post doc
Phone direct +45 4677 5045
Mobile 
address@hidden
 

   Wind Energy Department
 Risш National
  Laboratory for Sustainable Energy
TechnicalUniversityof Denmark #8211; DTU
Building 118, P.O. Box49
DK-4000 Roskilde, Denmark
Tel +45 4677 4677
Fax +45 4677 5083
www.risoe.dtu.dk

To it may concern,

I want to use GLPK-java to solve a simple MIP.

//    Maximize z =  17 * x1 + 12* x2

 

//    subject to

//    10*x1+7*x2 <= 40

//        x1+  x2 <= 5

//    where,

//    0.0 <= x1  integer

//    0.0 <= x2  integer

//  result: max=68: x1=4, x2=0;  ??

     

 

The code is shown as following. The problem is how I can get integer solution?

The result I got is:

Problem created

*     0: obj =  0.000000000e+000  infeas = 0.000e+000 (0)

*     2: obj =  6.833333333e+001  infeas = 0.000e+000 (0)

OPTIMAL SOLUTION FOUND

z = 68.33333333333334

x1 = 1.6666666666666676

x2 = 3.3333333333333326

 

%%%%%%%%%%%%%%%%%%source code%%%%%%%%%%%%%%

import java.io.File;

import java.io.IOException;

 

import org.gnu.glpk.GLPK;

import org.gnu.glpk.GLPKConstants;

import org.gnu.glpk.SWIGTYPE_p_double;

import org.gnu.glpk.SWIGTYPE_p_int;

import org.gnu.glpk.glp_prob;

import org.gnu.glpk.glp_smcp;

//import org.gnu.glpk.glp_intopt;

//import org.gnu.glpk.glp_iocp;

 

public class Integer1 {

//    Maximize z =  17 * x1 + 12* x2

 

//    subject to

//    10*x1+7*x2 <= 40

//        x1+  x2 <= 5

//    where,

//    0.0 <= x1  integer

//    0.0 <= x2  integer

//  result: max=68: x1=4, x2=0;  ??

     

      static

      {

   

    try

            {

              // try to load Linux library

                  System.loadLibrary( "glpk_java" );

            }

            catch (UnsatisfiedLinkError e)

            {

                  // try to load Windows library

                  System.loadLibrary("glpk_4_39_java");

            }

      }

 

      public static void main(String[] arg)

      {

            glp_prob mip;

            glp_smcp parm;

            SWIGTYPE_p_int ind;

            SWIGTYPE_p_double val;

            int ret;

     

 

//      Create problem       

            mip = GLPK.glp_create_prob();

            System.out.println("Problem created");

            GLPK.glp_set_prob_name(mip, "myProblem");

 

//      Define columns

            GLPK.glp_add_cols(mip, 2);

            GLPK.glp_set_col_name(mip, 1, "x1");

            GLPK.glp_set_col_kind(mip, 1, GLPKConstants.GLP_IV);

            GLPK.glp_set_col_bnds(mip, 1, GLPKConstants.GLP_LO, 0,0);

            GLPK.glp_set_col_name(mip, 2, "x2");

            GLPK.glp_set_col_kind(mip, 2, GLPKConstants.GLP_IV);

            GLPK.glp_set_col_bnds(mip, 2, GLPKConstants.GLP_LO, 0,0);

           

           

       

//      Create constraints

          GLPK.glp_add_rows(mip, 3);

 

            GLPK.glp_set_row_name(mip, 1, "c1");

            GLPK.glp_set_row_bnds(mip, 1, GLPKConstants.GLP_UP, 0, 40);

            ind = GLPK.new_intArray(3);

            GLPK.intArray_setitem(ind, 1, 1);

            GLPK.intArray_setitem(ind, 2, 2);

            val = GLPK.new_doubleArray(3);

            GLPK.doubleArray_setitem(val, 1, 10);

            GLPK.doubleArray_setitem(val, 2, 7);

            GLPK.glp_set_mat_row(mip, 1, 2, ind, val);

           

//         

            GLPK.glp_set_row_name(mip, 2, "c2");

            GLPK.glp_set_row_bnds(mip, 2, GLPKConstants.GLP_UP, 0, 5);

            ind = GLPK.new_intArray(3);

            GLPK.intArray_setitem(ind, 1, 1);

            GLPK.intArray_setitem(ind, 2, 2);

            val = GLPK.new_doubleArray(3);

            GLPK.doubleArray_setitem(val, 1, 1);

            GLPK.doubleArray_setitem(val, 2, 1);

            GLPK.glp_set_mat_row(mip, 2, 2, ind, val);

           

 

//      Define objective

            GLPK.glp_set_obj_name(mip, "z");

            GLPK.glp_set_obj_dir(mip, GLPKConstants.GLP_MAX);

      //    GLPK.glp_set_obj_coef(mip, 0, 0);

            GLPK.glp_set_obj_coef(mip, 1, 17);

            GLPK.glp_set_obj_coef(mip, 2, 12);

 

//    solve model

            parm = new glp_smcp();

            GLPK.glp_init_smcp(parm);

            ret = GLPK.glp_simplex(mip, parm);

           

//      Retrieve solution

                if (ret == 0) {

                 

                  write_lp_solution(mip);

            }

            else {

                  System.out.println("The problem could not be solved");

            };

           

            // free memory

            GLPK.glp_delete_prob(mip);

      }    

     

      /**

       * write simplex solution

       * @param lp problem

       */

      static void write_lp_solution(glp_prob mip)

      {

            int i;

            int n;

            String name;

          double val;

            //int val;

            name = GLPK.glp_get_obj_name(mip);

            val  = GLPK.glp_get_obj_val(mip);

            //val  = GLPK.glp_mip_obj_val(mip);

            System.out.print(name);

            System.out.print(" = ");

            System.out.println(val);

            n = GLPK.glp_get_num_cols(mip);

            for(i=1; i <= n; i++)

            {

                  name = GLPK.glp_get_col_name(mip, i);

                  val  = GLPK.glp_get_col_prim(mip, i);

                  //val  = GLPK.glp_mip_col_val(mip, i);

                  System.out.print(name);

                  System.out.print(" = ");

                  System.out.println(val);

            }

      }

 

}

 

 

 

Yi Zong Post doc Phone direct +45 4677 5045 Mobile address@hidden

Wind Energy Department Risø National Laboratory for Sustainable Energy Technical University of Denmark – DTU Building 118, P.O. Box 49 DK-4000 Roskilde, Denmark Tel +45 4677 4677 Fax +45 4677 5083 www.risoe.dtu.dk