[Bug-glpk] row deletion bug

[Balazs DEZSO]

Dear GLPK Developers,

The row and column deletion does not work properly. The attached example shows 
that the second solution could not be calculated with glpk. I debugged the 
library and I found out that the row and the col "stat"s was not reset (so 
the stat stayed LPX_BS) when I erase a row or col from the problem. And in
the next lpx_warm_up one more or less basis will be in the matrix and it will 
cause a failure in the library. Proper solution could be the resetting the 
stats by the row/col type or the proper decreasing of the initial basis.

Best, Balazs

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

#define NI 0
#define NV 0.0

#define NC 6

int ia[] = { NI,
  1, 1,
  2, 2,
  3, 3
};

int ja[] = { NI, 
  1, 2,
  1, 2,
  1, 2
};

double va[] = { NV,
  2, 1,
  1, 2,
  2, 2
};

double rub[] = { NV,
  3,
  3,
  2
};

int rea[] = { NV, 3 };

int main() {
  LPX* lp;
  lp = lpx_create_prob();

  lpx_add_cols(lp, 2);
  lpx_set_col_bnds(lp, 1, LPX_LO, 0.0, NV);
  lpx_set_col_bnds(lp, 2, LPX_LO, 0.0, NV);
  lpx_set_col_name(lp, 1, "x1");
  lpx_set_col_name(lp, 2, "x2");
  lpx_set_col_bnds(lp, 1, LPX_LO, 0.0, NV);
  lpx_set_col_bnds(lp, 2, LPX_LO, 0.0, NV);

  lpx_set_obj_coef(lp, 1, 1.0);
  lpx_set_obj_coef(lp, 2, 1.0);
  lpx_set_obj_dir(lp, LPX_MAX);

  lpx_add_rows(lp, 3);
  lpx_set_row_bnds(lp, 1, LPX_UP, NV, rub[1]);
  lpx_set_row_bnds(lp, 2, LPX_UP, NV, rub[2]);
  lpx_set_row_bnds(lp, 3, LPX_UP, NV, rub[3]);

  lpx_load_matrix(lp, NC, ia, ja, va);

  lpx_simplex(lp);

  lpx_print_prob(lp, "prob1");
  lpx_print_sol(lp, "sol1");

  lpx_del_rows(lp, 1, rea);
  
  lpx_simplex(lp);

  lpx_print_prob(lp, "prob2");
  lpx_print_sol(lp, "sol2");

  lpx_delete_prob(lp);

  return 0;
}

glpk_test.c
Description: Text Data