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## Re: [Bug-glpk] write_freemps does not write objective function coefficie

**From**: |
Andrew Makhorin |

**Subject**: |
Re: [Bug-glpk] write_freemps does not write objective function coefficients |

**Date**: |
Wed, 4 Jul 2007 14:25:23 +0400 |

>* Trying to debug a stack error in GLPK, I am writing the problem out at*
>* every iteration of a column generation scheme*
>* Initially only in the free mps format, but then also in the lp format*
>* One major and one minor error occur:*
>* major: write_freemps does not write the objective function coefficients,*
This is not a bug. If the instance has at least one free (unbounded)
row, by default lpx_write_mps does not write the objective row assuming
that that free row is the objective row. In order to tell lpx_write_mps
to write the objective row in any case you should change the control
parameter LPX_K_MPSOBJ as follows:
lpx_set_int_parm(lp, LPX_K_MPSOBJ, 1);
For more details please see the glpk reference manual.
>* no column has a non-zero in the objective function*
>* minor: write_cpxlp creates one extra variable in the bounds section that*
>* does not appear anywhere else in the problem statement*
That variable exists in the problem object, however, its column is
empty (as seen in mps file).