DISCRETA

Anton Betten, Evi Haberberger, Reinhard Laue, Alfred Wassermann:

Here we want to give you a short survey on how you can work with DISCRETA and construct designs (for the description of the Kramer-Mesner method we use, click here ).

After the start of the program you get the main DISCRETA window:

First of all you should choose a group by clicking on the button "group". The different details for the group selection are described at this page. Together with the desired automorphism group you automatically prescribe the point set of the design: it is fixed as V = {1, ..., v} where v is the degree of the group.
As soon as you have prescribed an automorphism group, you have to specify the other parameters of the design: blocksize k, t and lambda. Click here for more information on the choice and the restrictions for the parameters.
Now you can start the calculation of the Kramer-Mesner matrix . This matrix M shows the incidence relations between the orbits of the prescribed group on the t-subsets (rows) and the orbits on the k-subsets of V (columns).
Finding designs with the given parameter set is then equivalent to solving the equation M · v = (lambda, ..., lambda)^T with the Kramer-Mesner matrix M. So the next thing to do is to start one of the given solvers for this system of diophantine equations.

Last updated: August 24, 1999, Evi Haberberger