### 33.1.1. Overview of Defining CFX-Solver Startup

To define how a CFX-Solver can be started, the number of settings that you need to set up for Execution Control depends on the case:

- In some cases, you need to specify only the name of a CFX-Solver input file (`*.def` or `*.mdef`). For cases that require initialization from previous results, you also need to specify the name of a results file (`*.res`).

- You can configure runs in serial or parallel:

  - Serial run is the default way of running a CFD case. During a serial run, all computation is done by a single process running on one processor.

  - Parallel run partitions the computation into more than one process and is done on more than one processor in a single machine (local parallel processing) or on more than one machine (distributed parallel processing). You also have the option of specifying how the computation is partitioned for a parallel run.

- You can optionally select the system priority for the interpolator and solver computation as well as settings such as precision and memory allocation.

When you have finished defining how CFX-Solver will start, click OK or Apply to save the settings.

Details of the above steps are described in the next section.

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