/*
 * simple_glpk.c
 *
 *   A file demonstrating the GLPK API.
 *
 */

#include <stdio.h>
#include <stdlib.h>
#include "glpk.h"

int 
main( void )
{
  /* Pointer to the lp object */
  LPX *lp;
  int ret;  /* return code */
  char *filename = "p0033.mps";
  int columns[2];

  /* Read in an instance from an MPS file */
  lp = lpx_read_mps( filename );
  /* lp = lpx_read_freemps( filename ); */

  /* Check that we read it correctly */
  if (lp == NULL)
    {
      printf("Error reading file %s\n", filename);
      exit(1);
    }

  /* Solve the (relaxation of the) problem */
  ret = lpx_simplex(lp);

  /* Check the solution */
  if ( ret == LPX_E_OK && lpx_get_status(lp) == LPX_OPT )
    { 
      printf("Found optimal solution!\n"); 
      printf("Objective value is %lf.\n", lpx_get_obj_val(lp) );
    }

  /***************************/
  /* Remove the first column */
  /* This will fail, but if you change the index to a 2, it will succeed */
  columns[1]=1;
  lpx_del_cols( lp, 1, columns );
  
  /* Re-solve */
  ret = lpx_simplex(lp);

  /* Check the solution */
  if ( ret == LPX_E_OK && lpx_get_status(lp) == LPX_OPT )
    { 
      printf("Resolved and found optimal solution!\n"); 
      printf("Objective value is %lf.\n", lpx_get_obj_val(lp) );
    }
  else
    {
      printf("Something went wrong during resolve.\n");
    }

  return 0;
}