# How to "Solve" Solver Optimization Mix Problem Errors

• 01-10-2019, 11:15 AM
ChrisHook
How to "Solve" Solver Optimization Mix Problem Errors
Hello all,

I'm a little new to solver, so i'm probably missing something very simple, but here's my problem.

I have a list of technologies with associated capabilities (score of 1-5). I have a set of requirements for said capabilities (score of 1-5). I have costs associated with each technology.

I would like to run solver to find the most optimal combination of capabilities such to maximize the total score, given a cost constraint.

However, when I run Solver in the attached, I keep getting either a linearity error or a "solver cant find solution". I know there's at least a feasible solution (I've done it myself).

Best,
Chris
• 01-10-2019, 11:35 AM
63falcondude
Re: How to "Solve" Solver Optimization Mix Problem Errors
Try this:

D24 =SUMIF(Table1[Selected? 0 or 1],1,Table1[Cost])

Then run the solver.

I get B7 = 6.9166
• 01-10-2019, 11:42 AM
ChrisHook
Re: How to "Solve" Solver Optimization Mix Problem Errors
Hi falcondude,

Thanks for the quick reply. I tried your suggestion and got 2.6, Then I changed the constraint to 43k and got a linearity error. See attached.
• 01-10-2019, 11:57 AM
63falcondude
Re: How to "Solve" Solver Optimization Mix Problem Errors
Hmm. I'm not sure why you would have gotten 2.6.

I did have to recreate the formulas in D26:M26 using MAX and IF since I don't have the MAXIFS function.

See attached.

As far as the linearity error is concerned, I am getting that on my end as well when I lower the constraint to anything less than 318,473.

I'm not too familiar with the different types of solving methods. I'll see if someone knows more about them.
• 01-10-2019, 12:03 PM
63falcondude
Re: How to "Solve" Solver Optimization Mix Problem Errors
It seems to work when I change the solving method to Evolutionary but it takes a couple of minutes.
• 01-10-2019, 12:54 PM
ChrisHook
Re: How to "Solve" Solver Optimization Mix Problem Errors
That's interesting - works for me as well.

I'll have to do a bit of reading to see what the difference is. Thank you for taking the time to help out!
• 01-10-2019, 01:09 PM
63falcondude
Re: How to "Solve" Solver Optimization Mix Problem Errors
You're welcome. Happy to help.