I am trying to solve a non-linear, non-smooth optimization in excel. Both GRG and Evolutionary algorithms are not able to give reasonable results(they are not converging in certain cases). The number of constraints are within the excel recommended limits and the model construct is correct. What is the next best option I have to run this optimization problem in excel? Is it better to go for Frontline Premium Solver platform(which have more solver engines than excel solver) or are there any better third party solver add-ins ?. Please give recommendations.
PS: Moving this out of excel is not an option for me.