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## [Help-glpk] formulation of a problem

**From**: |
Nico Moser |

**Subject**: |
[Help-glpk] formulation of a problem |

**Date**: |
Thu, 22 Jun 2006 13:33:11 +0200 |

Hi,

`I'm in trouble with set in a problem in the glpk datastructure and I
``can't find answers to my questions (perhaps I looked at the wrong
``places).
`The two main problems:
1. How can I set a variable to the right hand side?
If I have a constraint like this: x1+x2 <= y1 I can't set:
lpx_set_row_name(lp, 3, "constraint");
lpx_set_row_bnds(lp, 3, LPX_UP, 0, y1);

`2. How can I set 'holes' in the matrix (if a variable is not needed
``in one constraint)?
`
For instance:
x1+x2 = 3
x1 <= 1
then I would think the array assignments looks like that:
ia[1] = 1, ja[1] = 1, ar[1] = 1.0;
ia[2] = 1, ja[2] = 2, ar[2] = 1.0;
ia[3] = 2, ja[3] = 1, ar[3] = 1.0;
ia[4] = 2, ja[4] = 2, ar[4] = 0; // <- it doesn't work

`(a similar problem: if I don't need a basic variable in the minimize
``or maximize funktion, can I set the the coefficient to zero? like:
``lpx_set_obj_coef(lp,1,0.0); )
`
Thanks a lot,
Nico

**[Help-glpk] formulation of a problem**,
*Nico Moser* **<=**