A tracking unit includes a register for storing initial sequences and an accumulator for effecting a statistical treatment of the initial sequences, and ensures the statistical treatment relates to no more than a number of best sequences based on an evaluating algorithm. A generating unit employs the statistical treatment to present a new sequence. A measuring unit evaluates the new sequence according to the algorithm and cooperates with the tracking unit to effect providing the new sequence to the tracking unit when the evaluating indicates the new sequence is appropriate for the storing and statistical treatment. The measuring unit provides the new sequence to a regulating unit with an indication of efficacy of the new sequence. The regulating unit employs the indication to store a best-sequence-yet-received and responds to a criterion to order the generating unit to present a new sequence or to present the best-sequence-yet-received at an output locus.