Re: [Help-glpk] is it possible to determine the value a nb variable will take?

[Andrew Makhorin]

>> Lpx_warm_up computes the basis factorization only if it does not exist,
>> i.e. if glp_bf_exists returns zero.

> Does changing the status of a basic variable to
> nonbasic cause glp_bf_exists to return nonzero?

Yes. Any changes in the problem object that change the current basis
matrix invalidate the factorization. For example, changing the status
of a basic variable to a non-basic and vice versa, changing the basic
column of the constraint matrix, changing the row of the constraint
matrix which changes at least one basic column, etc.

>> Yes, there must be added an api routine to update the factorization
>> on changing the basis when a specified basic variable leaves the basis
>> and a non-basic one enters it.

> For what I have in mind, I need to specify
> both the entering and leaving variables.

I meant an api routine similar to CPXpivot (used in cplex). Such
routine exists (it is used internally by the simplex method routines),
however, it is not available on api level.