Adjustments to Software Settings

Jeremy DysonBasel, Switzerland

Why Are Adjustments Necessary?

„Optimisation is the science of selecting the best of many possible decisions in a complex real-life environment“

Mordecai Avriel

Nonlinear Programming

Optimisation

Minimise the Value of the Function

N [Data Valuei – Modelled Valuei]2

i = 1

• When the function is solved numerically (normally) rather than analytically, this means that the solution is only as exact as you make it, and it depends on:– Search method, e.g. Marquardt algorithm, for the solution

– Settings for search method, including initial parameter values

– How the modelled values are calculated

– Settings to finish the search, i.e. an acceptable solution

Settings may need adjusting to find global minimum

ModelMaker – Marquardt Settings

• Convergence Change– The size of a convergence step (0.1)

• Convergence Steps– Number of convergence step before optimisation stops (50)

• Retry Count– Number of times optimisation retries convergence steps (50)

• Initial Lamda– Initial value determines „initial steepness“ of the search (0.01)

• Minimum Change– Minimum change in Lambda (0.00001)

• Fractional Change– Fractional change in Lambda (0.01)

ModelMaker – Simulated Annealing

• Why is it needed?– If the Marquardt Settings cannot find the global minimum

• When is it likely to be needed?– Initial parameter values inappropriate

– Model has a complex minimisation function, e.g. HS kinetics

• What does it do?– Tries many combinations of initial parameter values

Acknowledgement

Dr Rene Oscar Kühne for teaching me ModelMaker