# Computation algorithms

When setting up a simulation in CENOS, you will see in SIMULATION CONTROL that you are given a **choice of selecting computation algorithm**.

In this article we will take a look behind the computation algorithms, **understand their differences** and find out **in which situations to use which algorithm**.

## Fast

The Fast algorithm (also weak coupling, one way coupling) **calculates electromagnetic sources once and apply them to the thermal model**. Reverse interaction (change of electromagnetic properties due to heating) is not taken into account.

The fast algorithm gives good results if the **time step is small** compared to the heating rate.

Schematic of the calculation with **Fast**:

## Accurate

The accurate algorithm uses two-way coupling - **electromagnetic sources are recalculated according to the temperature field** until convergence is reached.

The accurate algorithm gives **very precise results** with rougher time step size and is important for highly nonlinear problems.

Schematic of the calculation with **Accurate**:

## Automatic

Automatic algorithm switches between **Fast** and **Accurate** according to user input:

**Fast if**materials have constant permeability and electrical conductivity;**Accurate if**materials have nonlinear magnetic properties (**B-H model**and/or**temperature dependence**) and temperature dependent electrical conductivity.