Excel Solver: Simplex LP. Constraints are not respected

Hi Forum

I've spent the last 3 weeks trying to get the Solver to give me the correct result and respect the constraints that i have defined.

My current issue is, that the values in F:46-51 must not excede those present in B:46-51
It though keeps ignoring this constraint (Answer report says it is binding, and even the formula shown there says it must not be larger than)

I have rebuilt the model 4 times now, but i cannot rootcause the problem...

Anyone who could be so kind as to lead me in the correct direction?


Have a nice weekend
Br
Mathias

As you have a mix of small numbers (binerys) and numbers in the range of millions it seems like the excel solve can't cope with this. So in Solver click on the "Options" button and under tab "All Methods" tick box marked "Used Automatic Scaling" and that should fix your problem.

In your closed thread I thought it was the size of you model that was the problem but that was not right. Still comparing the two result it seems that OpenSolver met all criteria with a total cost of 1353975000 as compared to the excel solvers 1354096000 giving a difference of 121000 as well as not being sensitive to the spread in numbers.

So if you wish to match the excel solver's result with OpenSolver you can either change "Constraint Precision" settings or set "Integer Optimality" to 0 and who knows perhaps this solver result may impress you teacher.

Alf