src/work/athos/lp/lp_sample.cc
author athos
Mon, 11 Apr 2005 15:46:14 +0000
changeset 1339 26a88d12d1a6
parent 1318 88edb143a87a
permissions -rw-r--r--
A little has been done. Some important questions arised.
     1 #include <iostream>
     2 #include <lemon/lp_glpk.h>
     3 using namespace lemon;
     4 
     5 int main()
     6 {     
     7  //The following example is taken from the documentation of the GLPK library.
     8  //See it in the GLPK reference manual and among the GLPK sample files (sample.c)
     9   LpGlpk lp;
    10   typedef LpGlpk::Row Row;
    11   typedef LpGlpk::Col Col;
    12 
    13   lp.max();
    14 
    15   Col x1 = lp.addCol();
    16   Col x2 = lp.addCol();
    17   Col x3 = lp.addCol();
    18 
    19   //One solution
    20   //   Row p = lp.addRow();
    21   //   Row q = lp.addRow();
    22   //   Row r = lp.addRow();
    23   //   lp.setRow(p,x1+x2+x3 <=100);  
    24   //   lp.setRow(q,10*x1+4*x2+5*x3<=600);  
    25   //   lp.setRow(r,2*x1+2*x2+6*x3<=300);  
    26 
    27   //A more elegant one
    28   //Constraints
    29   lp.addRow(x1+x2+x3 <=100);  
    30   lp.addRow(10*x1+4*x2+5*x3<=600);  
    31   lp.addRow(2*x1+2*x2+6*x3<=300);  
    32   //Nonnegativity of the variables
    33   lp.colLowerBound(x1, 0);
    34   lp.colLowerBound(x2, 0);
    35   lp.colLowerBound(x3, 0);
    36   //Objective function
    37   lp.setObj(10*x1+6*x2+4*x3);
    38   
    39   lp.solve();
    40 
    41   if (lp.primalStatus()==LpSolverBase::OPTIMAL){
    42     printf("Z = %g; x1 = %g; x2 = %g; x3 = %g\n", 
    43 	   lp.primalValue(), 
    44 	   lp.primal(x1), lp.primal(x2), lp.primal(x3));
    45   }
    46   else{
    47     std::cout<<"Optimal solution not found!"<<std::endl;
    48   }
    49 
    50 
    51   //Here comes the same problem written in C using GLPK API routines
    52 
    53 //   LPX *lp;
    54 //       int ia[1+1000], ja[1+1000];
    55 //       double ar[1+1000], Z, x1, x2, x3;
    56 // s1:   lp = lpx_create_prob();
    57 // s2:   lpx_set_prob_name(lp, "sample");
    58 // s3:   lpx_set_obj_dir(lp, LPX_MAX);
    59 // s4:   lpx_add_rows(lp, 3);
    60 // s5:   lpx_set_row_name(lp, 1, "p");
    61 // s6:   lpx_set_row_bnds(lp, 1, LPX_UP, 0.0, 100.0);
    62 // s7:   lpx_set_row_name(lp, 2, "q");
    63 // s8:   lpx_set_row_bnds(lp, 2, LPX_UP, 0.0, 600.0);
    64 // s9:   lpx_set_row_name(lp, 3, "r");
    65 // s10:  lpx_set_row_bnds(lp, 3, LPX_UP, 0.0, 300.0);
    66 // s11:  lpx_add_cols(lp, 3);
    67 // s12:  lpx_set_col_name(lp, 1, "x1");
    68 // s13:  lpx_set_col_bnds(lp, 1, LPX_LO, 0.0, 0.0);
    69 // s14:  lpx_set_obj_coef(lp, 1, 10.0);
    70 // s15:  lpx_set_col_name(lp, 2, "x2");
    71 // s16:  lpx_set_col_bnds(lp, 2, LPX_LO, 0.0, 0.0);
    72 // s17:  lpx_set_obj_coef(lp, 2, 6.0);
    73 // s18:  lpx_set_col_name(lp, 3, "x3");
    74 // s19:  lpx_set_col_bnds(lp, 3, LPX_LO, 0.0, 0.0);
    75 // s20:  lpx_set_obj_coef(lp, 3, 4.0);
    76 // s21:  ia[1] = 1, ja[1] = 1, ar[1] =  1.0; /* a[1,1] =  1 */
    77 // s22:  ia[2] = 1, ja[2] = 2, ar[2] =  1.0; /* a[1,2] =  1 */
    78 // s23:  ia[3] = 1, ja[3] = 3, ar[3] =  1.0; /* a[1,3] =  1 */
    79 // s24:  ia[4] = 2, ja[4] = 1, ar[4] = 10.0; /* a[2,1] = 10 */
    80 // s25:  ia[5] = 3, ja[5] = 1, ar[5] =  2.0; /* a[3,1] =  2 */
    81 // s26:  ia[6] = 2, ja[6] = 2, ar[6] =  4.0; /* a[2,2] =  4 */
    82 // s27:  ia[7] = 3, ja[7] = 2, ar[7] =  2.0; /* a[3,2] =  2 */
    83 // s28:  ia[8] = 2, ja[8] = 3, ar[8] =  5.0; /* a[2,3] =  5 */
    84 // s29:  ia[9] = 3, ja[9] = 3, ar[9] =  6.0; /* a[3,3] =  6 */
    85 // s30:  lpx_load_matrix(lp, 9, ia, ja, ar);
    86 // s31:  lpx_simplex(lp);
    87 // s32:  Z = lpx_get_obj_val(lp);
    88 // s33:  x1 = lpx_get_col_prim(lp, 1);
    89 // s34:  x2 = lpx_get_col_prim(lp, 2);
    90 // s35:  x3 = lpx_get_col_prim(lp, 3);
    91 // s36:  printf("\nZ = %g; x1 = %g; x2 = %g; x3 = %g\n", Z, x1, x2, x3);
    92 // s37:  lpx_delete_prob(lp);
    93 //       return 0;
    94 
    95   return 0;
    96 }