Originally posted by: gtoptimizer

For a "ranged constraint", i.e. a constraint whose type as returned by CPXgetsense is 'R', what does CPXgetrhs return?

Thanks!

Originally posted by: T_O

I think it will return the lower bound of the constraint if the range value (CPXXgetrngval) is positive and the upper bound if the range value is negative (don't know whether this will ever happen).

Best regards,
Thomas

It just returns the right-hand side that you set for this range constraint. You may want to take a look at the reference documentation of CPXXnewrows to understand how a range constraint is defined by means of the rhs and rngval properties.

Originally posted by: T_O

Daniel,

I think the documentation is a little imprecise here. CPXnewrows says:

"the value of constraint i can be between rhs[i] and rhsi[i]+rngval[i]"

CPXcopylp says:

"If rngval[i] > 0, then row i activity is in [rhs[i],rhs[i]+rngval[i]], and if rngval[i] <= 0,then row i activity is in [rhs[i]+rngval[i],rhs[i]]."

While mathematically both mean the same, the first one could imply that rngval[i] is always positive. Can you say a few words concerning negative values?

Best regards,
Thomas

rngval[i] is explicitly allowed to be negative.

If rngval[i] is negative, then rhs[i] is the upper bound of the constraint and rhs[i]+rngval[i] is the lower bound.

If rngval[i] is positive, then rhs[i] is the lower bound of the constraint and rhs[i]+rngval[i] is the upper bound.

This implies that there are always two ways to specify the bounds of a range constraint L <= ax <= U. Either rhs=L and rngval=U-L or rhs=U and rngval=L-U.

We will try to make this crystal clear in the docs.