"solver" function that is in Excel

[md]

I am looking for a VI that performs like the "solver" add-in that Excel has.

[BrandonS]

The solver add-in is Excels optimization program. In LabVEIW there are optimization VIs. They are found under Functions >> Mathematics >> Optimization. I have used the Conjugate Gradient nD VI in a similar way to the solver.

[Chatwin]

The important difference between Excel Solver and the conjugate gradient optimizer is that Excel doesn't require the user to form the gradient.  What's that about?

[DFGray]

Different minimizers require different inputs.  Conjugate gradient methods require derivatives (although they can be computed numerically - with a decrease in speed and algorithmic stability).  I prefer the downhill simplex for its stability and ease of use, but it is significantly slower than the conjugate gradient.

For a fairly complete explanation of various minimizer/maximizer functions, check out Numerical Recipes in C, chapter 10.

[Chatwin]

Is there a minimizer in LabVIEW that, like Excel Solver, doesn't require me to compute my (error) derivative as well as my (error) function?

[DFGray]

Yes.  Downhill Simplex nD.vi will do it, but you need at least the full version of LabVIEW to have it.  You need to supply starting values, requested accuracy, and function.  I would recommend reading about the method in the above link to Numerical Recipes.  Like all minimizers, there are some tricks to make it work well.

Note: If you have the base version of LabVIEW, it is relatively easy to code the downhill simplex yourself using the methods in Numerical Recipes.
Disclaimer: I have a PhD in physics, so the above statement must be taken with a grain or two of salt .  Let us know if you need more help.

[Chatwin]

I did try it, it wasn't working... got it now-- I was passing garbage into the routine and it couldn't converge.