## Friday, June 14, 2019

### A Java Container for Parameters

A few days ago, I posted about a Swing class (and supporting stuff) that I developed to facilitate my own computations research, and which I have now made open-source in a Bitbucket repository. I finally got around to cleaning up another Java utility class I wrote, and which I use regularly in experiments. I call it ParameterBlock. It is designed to be a container for various parameters that I need to set during experiments.

It might be easiest if I start with a couple of screen shots. The first one shows a Swing application I was using in a recent project. Specifically, it shows the "Settings" menu, which has multiple entries corresponding to different computational stages (the overall solver, an initial heuristic, two phases of post-heuristic number crunching), along with options to save and load settings.

Computational research can involve a ton of choices for various parameters. CPLEX alone has what seems to be an uncountable number of them. In the Dark Ages, I hard-coded parameters, which meant searching the source code (and recompiling) every time I wanted to change one. Later I graduated to putting them on the command line, but that gets old quickly if there are more than just a handful. When I started writing simple Swing platforms for my work (like the one shown above), I added menu options to call up dialogs that would let me see the current settings and change them. Over time, this led me to my current solution.

I put each collection of parameters in a separate subclass of the (abstract) ParameterBlock class. So clicking on "Solver" would access on subclass, clicking on "Heuristic" would access a different subclass, and so on. A parameter block can contain parameters of any types. The next shot shows a dialog for the solver parameters in my application. Two of the parameters are boolean (and have check boxes), two are Java enumerations (and have radio button groups), and three are numeric (and have text fields). String parameters are also fine (handled by text boxes).

Defining a parameter block is easy (in my opinion). It pretty much boils down to deciding how many parameters you are going to have, assigning a symbolic name to each (so that in other parts of the code you can refer to "DOMINANCE" and not need to remember if it parameter 1, parameter 2 or whatever), giving each one a label (for dialogs), a type (such as boolean.class or double.class), a default value and a tool tip. The ParameterBlock class contains a static method for generating a dialog like the one below, and one or two other useful methods.

 Solver parameters

You can more details in the README file at the Bitbucket repository I set up for this. The repository contains a small example for demonstration purposes, but to use it you just need to copy ParameterBlock.java into your application. As usual, I'm releasing it under a Creative Commons license. Hopefully someone besides me will find it useful.