## 17.4. Parallel - Automatic Decomposition of Euler parts

The automatic decomposition algorithm also incorporates Euler
parts, Ideal Gas as well as Multi-material, in addition to its ability
to handle unstructured grids. This facilitates the decomposing of
complicated Euler/Lagrange coupled models—you need only stipulate
the number of tasks over which the model should be assigned and Autodyn will
automatically produce a decomposition configuration with good load
balancing qualities and minimal inter-processor communication. Furthermore,
to further enhance the efficiency of coupled calculations the subdomains
of the Lagrange structure will be placed on the same processor, so
decreasing the necessary inter-processor communication.

To automatically decompose an Euler model, go to the Parallel
dialog panel as seen below, activate parallel processing and add a
new decomposition set which in this instance is called 'two':

Click the **Set Decomposition** button and all Euler parts will be shown in the **Automatic Decomposition** dialog window:

Input the number of tasks you want to decompose the part over
and click the **Decompose Now** button.
In this case the number of tasks is two and the following decomposition
can be viewed:

More complicated decompositions can also be easily achieved.
Here the part is decomposed over 16 tasks:

As previously stated, the new algorithm allows easy decomposition
of complicated coupled models which include Euler and unstructured
Lagrange Parts. The model below contains a brick structure in which
an explosion is occurring. The brick structure is modeled using Lagrangian
parts, while the explosion in air is modeled using an Euler part.
Here, only the lower region of the Euler part is shown for illustration
purposes; the Euler part extends above the brick structure.

The **Decomposition Set** window
dialog will contain all of the parts and by default they will all
be highlighted:

By choosing decomposing the model over 4 tasks, the various
parts can be assigned to the available processors whilst ensuring
efficient parallel computations:

If you want to override this decomposition, then the Euler part
can still be manually decomposed as before.