[Help-glpk] LPX_E_SING Error on 64bit Platform

[Volkan YAZICI]

Hi,

While trying to solve attached ILP problem as below:

  int
  main(void)
  {
      glp_prob *lp;
  
      lp = glp_create_prob();
      assert(!glp_read_lp(lp, NULL, "repl-ilp-xXNtiz"));
  
      assert(!glp_simplex(lp, NULL) && glp_get_status(lp) == GLP_OPT);
      lpx_set_int_parm(lp, LPX_K_USECUTS, LPX_C_ALL);
      lpx_set_real_parm(lp, LPX_K_TMLIM, 1);
      lpx_adv_basis(lp);
      {
          int ret = lpx_intopt(lp);
          assert(ret == LPX_E_OK || ret == LPX_E_TMLIM);
      }
  
      return 0;
  }

The final assertion fails with "ret" set to 211 (LPX_E_SING). Below is
the program output:

  glp_read_lp: reading problem data from `repl-ilp-xXNtiz'...
  glp_read_lp: 101 rows, 166 columns, 531 non-zeros
  glp_read_lp: 166 integer columns, all of which are binary
  glp_read_lp: 272 lines were read
  *     0:   objval =   0.000000000e+00   infeas =   0.000000000e+00 (0)
  *   124:   objval =   3.702857143e+01   infeas =   8.881784197e-16 (0)
  OPTIMAL SOLUTION FOUND
  lpx_adv_basis: size of triangular part = 101
  ipp_basic_tech:  0 row(s) and 0 column(s) removed
  ipp_reduce_bnds: 1 pass(es) made, 0 bound(s) reduced
  ipp_basic_tech:  0 row(s) and 0 column(s) removed
  ipp_reduce_coef: 1 pass(es) made, 0 coefficient(s) reduced
  lpx_intopt: presolved MIP has 101 rows, 166 columns, 531 non-zeros
  lpx_intopt: 166 integer columns, all of which are binary
  lpx_adv_basis: size of triangular part = 101
  Solving LP relaxation...
  *   124:   objval =   0.000000000e+00   infeas =   0.000000000e+00 (0)
  *   134:   objval =   3.702857143e+01   infeas =   0.000000000e+00 (0)
  OPTIMAL SOLUTION FOUND
  Creating the conflict graph...
  The conflict graph has 2*166 vertices and 535 edges
  Generating cutting planes...
  &   134: obj =   3.702857143e+01   frac =    33   cuts =     0 (0)
  &   331: obj =   2.800000000e+01   frac =    18   cuts =    81 (162)
  81 mixed cover cut(s) added
  Integer optimization begins...
  +   331: mip =     not found yet <=              +inf        (1; 0)
  Gomory's cuts enabled
  MIR cuts enabled
  +   394: >>>>>   2.700000000e+01 <=   2.800000000e+01   3.7% (4; 0)
  spx_invert: the basis matrix is singular
  spx_simplex: numerical problems with basis matrix
  spx_simplex: sorry, basis recovery procedure not implemented yet
  ios_driver: unable to solve current LP relaxation; glp_simplex returned 5
  +  1719: mip =   2.700000000e+01 <=   2.800000000e+01   3.7% (83; 31)
  glp_intopt: cannot solve current LP relaxation
  repl-k: src/ilp.c:153: solve_ilp: Assertion `ret == 200' failed.

The strange thing is, while above codes works perfectly on my notebook
(32bit), it fails to run on a remote server (64bit). Below are system
specifications of both machines.

  REMOTE-SERVER
  -------------
  $ gcc -v
  Using built-in specs.
  Target: x86_64-linux-gnu
  Configured with: ../src/configure -v --with-pkgversion='Debian 4.3.2-1.1' 
--with-bugurl=file:///usr/share/doc/gcc-4.3/README.Bugs 
--enable-languages=c,c++,fortran,objc,obj-c++ --prefix=/usr --enable-shared 
--with-system-zlib --libexecdir=/usr/lib --without-included-gettext 
--enable-threads=posix --enable-nls --with-gxx-include-dir=/usr/include/c++/4.3 
--program-suffix=-4.3 --enable-clocale=gnu --enable-libstdcxx-debug 
--enable-objc-gc --enable-mpfr --enable-cld --enable-checking=release 
--build=x86_64-linux-gnu --host=x86_64-linux-gnu --target=x86_64-linux-gnu
  Thread model: posix
  gcc version 4.3.2 (Debian 4.3.2-1.1)
  $ glpsol -v
  GLPSOL: GLPK LP/MIP Solver 4.29

  NOTEBOOK
  --------
  $ gcc -v
  Using built-in specs.
  Target: i486-linux-gnu
  Configured with: ../src/configure -v --with-pkgversion='Debian 4.3.2-1.1' 
--with-bugurl=file:///usr/share/doc/gcc-4.3/README.Bugs 
--enable-languages=c,c++,fortran,objc,obj-c++ --prefix=/usr --enable-shared 
--with-system-zlib --libexecdir=/usr/lib --without-included-gettext 
--enable-threads=posix --enable-nls --with-gxx-include-dir=/usr/include/c++/4.3 
--program-suffix=-4.3 --enable-clocale=gnu --enable-libstdcxx-debug 
--enable-objc-gc --enable-mpfr --enable-targets=all --enable-cld 
--enable-checking=release --build=i486-linux-gnu --host=i486-linux-gnu 
--target=i486-linux-gnu
  Thread model: posix
  gcc version 4.3.2 (Debian 4.3.2-1.1)
  You have new mail in /var/mail/vy
  $ glpsol -v
  GLPSOL: GLPK LP/MIP Solver 4.29

What might I be missing? Any ideas?


Regards.

repl-ilp-xXNtiz
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