Thank you so much for your response Chris. Your comments about isoutofdomain and the notion of passing the indecing to the function made it very clear, thank you. For the call back gotcha, I will upgrade and test again and report, thank you. Lastly, the post I was refering to about positive domain was this one, Domain Troubles with Differential Equations Solver (with non-auto-differentiable function inside the ODE def), here I saw positive domain potentially being used and passed as option, positive domain( 1.0 ) , I really did not quite get how to use positive domain from the that, or even the main definition , I will take another look soon, and especially once I have the call back library. - Thank you so much for your quick response and help. !!