Re: [Help-glpk] the API of GLPK, add_cols problem

[Andrew Makhorin]

> I have some questions about GLPK through the API.

> I have a variable like this :    2<=x<=5   ,through API,  I write it
> like this:

> glp_add_cols(lp,1);
> glp_set_col_name(lp,1,"x");
> glp_set_col_bnds(lp,1,GLP_LO,2.0,0.0);
> glp_set_col_bnds(lp,1,GLP_UP,0.0,5.0);

> or like this:

> glp_add_cols(lp,2);
> glp_set_col_name(lp,1,"x");
> glp_set_col_name(lp,2,"x");
> glp_set_col_bnds(lp,1,GLP_LO,2.0,0.0);
> glp_set_col_bnds(lp,2,GLP_UP,0.0,5.0);

> which is right?  

Neither. You should write as follows:

glp_set_col_bnds(lp, j, GLP_DB, 2., 5.);

Every call to glp_set_col_bnds discards previously defined bounds
of the variable.

> i do not know add 1 cols or add 2 cols .

One.