Would someone be able to explain the capabilities for the 'Number of Processes' option and how it is intended to be used? I am trying to render several options for shading options in various sizes and for a number of times throughout the year and am having trouble getting them to run simultaneously. Currently they are running in series and overwriting the previous run.
At the moment there's no way to run different geometries simultaneously, unless you use WriteOnly mode and launch the batch files yourself. As for overwriting results, that's a function of not providing a unique name to each design option. Take a look at the example file C:\DIVA\ExampleFiles\Grasshopper\Daylight\01_Visualization_D_ParametricGeom.gh. A name is provided for each option, in a data structure matching that of the scene input. The component will solve each data branch (i.e. geometry option) serially, causing one simulation to run after the other, as you observe.
Now, for that NP input. This determines the number of processes available to each loop through the solver, or, in your case, each shading option. The Visualization component does parallelize time series, so you can input a list of skies and those will render concurrently on NP threads (see C:\DIVA\ExampleFiles\Grasshopper\Daylight\01_Visualization_C_Skies.gh).