Starting a parameter space search

If the program calcsta has been set up, the parameter space may be searched by the program searchspace. It is started by the command (in the example you should go to the directory /mcphas/examples/cecu2a/fit) :

searchspace 0 mcphas.jjj [and possible other input parameter files].

Note that the user written program calcsta has to be in the directory where searchspace is started from. The ''0'' in the command means that the search is started for the first time. The program generates an output file searchspace.0 with a list of parameter sets. This list may be shortened to stop searching some regions of the parameter space and subsequently the program may be started with

searchspace 1 mcphas.jjj [and possible other input parameter files].

Now the values stored in searchspace.0 are read and the parameter space is searched in more detail and a longer list of parameters is stored as searchspace.1. This may be again edited to drop some regions of the parameter space and searchspace may be started with searchspace 2 ... and so on ....

The program creates new parameter sets from an old set by incrementing/decrementing each of the parameters subsequently by a small step. In the first level this step is just equal to a quarter of the parameter range. Going from one level to the next this step is halved. Figure 17.1 shows how a two dimensional parameter space is covered by this procedure. If all neighbouring points of a given point show a larger value of sta, then the set is recorded, because it might be near a minimum of sta. The parameter values are stored in the file results/searchspace.searchspace-level.localminima.

Martin Rotter 2017-01-10