Solver constraints with OR function

[isabel80]

Hi

I am using solver to find the optimal volumes of products from different suppliers to total 100% of required volumes at minimum costs.

My target cell is the total cost set to minimum.

My changing cells are the volumes of product with each supplier.

My constraints are:

- Total volume must be equal to 100%
- Volume must be less than or equal to maximum volume available from supplier
- Volume must be more than or equal to minimum volume available from supplier OR volume must be zero

Is it possible to set up the 'OR' function?

Thanks

Isabel

 

[swat2]

I solved this by adding some additional columns. Beside your amount orded column, add another column I'll call "USE" . This will be filled with 1's and 0's by solver. Beside that I have the "Bought" Column which is just the product of the Ordered column and the Use Column. The sum of the Bought column is what I use as the target cell. Your cost should be the "Bought Column times the Price column and you sum this up for for your target cell. Allow solver to change the values in the Amount column AND the Use column.

Constraints should have your 100% for the bought column, minimum in Order column is min order from supplier, max in order column should be maximumn from supplier. Also make them integers if you want. The key part here is to make the USE column a binary constraint so it will choose a 1 or 0.

Allow to solve and solver will have to at least do the minimum from a supplier and if it doesn't need that minimum inventory it will change the USE cells to 0 to reduce costs. Hopefully you can solve your problem with my convoluted explanation.