4.6 Optimizer Module Interactions

Optimizers have a crucial role in the simulation environment. They request simulations at particular parameter values and use therefore resulting data for further evaluations.

Figure 4.20: Interactions between the optimizer and the framework. By means of stdin, stdout, and stderr redirection the optimization protocol is established.

In Figure 4.20 the interaction between the optimizer module and the program executable is shown. In the initial step an input deck for the optimizer, out of the variables defined in the experiment file and model, is created. In this file^4.9 all needed data for the optimizer, like the starting point, the parameter ranges, and the termination criteria are stored. Then the task is queued and the framework starts the program as soon as a free host is available. For the communication between the framework and the optimizer, a communication protocol is used. Three connections between the job and the framework are opened. An output stream of the framework is connected to the stdin of the job and the stdout and stderr are connected to two input steams. Over these connections the optimizer protocol is established and data like requests, results, and the optimal parameter settings are transmitted. Finally the termination of the executable is analyzed, whether an error occurred or if it succeeded. In the output file additional information about the optimization process is written which is mainly used for debugging purpose.

Footnotes

... file^4.9

The syntax of these files is described in Appendix F and Appendix H