https://ir.unisa.ac.za/handle/10500/23878 2026-05-05T15:30:42Z 2026-05-05T15:30:42Z Wessels, LFA Barnard, E Van Rooyen, E https://ir.unisa.ac.za/handle/10500/23955 2018-05-20T01:00:42Z 1991-01-01T00:00:00Z

The physical correlates of local minima Wessels, LFA; Barnard, E; Van Rooyen, E The training of neural-net classifiers is often hampered by the occurrence of local minima, which results in the attainment of inferior classification performance. We study the problem of local minima in order to devise means of alleviating it. In order to establish a better understanding of the problem, the nature of the physical states of neural nets stuck in local minima, is investigated. We show that the occurrence of a local minimum in the crite­rion function can often be related to specific patterns of defects in the classifier. In particular, three main causes for local minima are identified. Such an understanding of the physical correlates of local minima is important, since it suggests sensible ways of choosing the weights from which the training process is initiated.

1991-01-01T00:00:00Z Von Solms, S.H. Ehlers, E.M. Enslin, DJ https://ir.unisa.ac.za/handle/10500/23954 2018-06-06T11:42:53Z 1991-01-01T00:00:00Z

Knowledge representation using formal grammars Von Solms, S.H.; Ehlers, E.M.; Enslin, DJ In this paper, formal grammars, specifically random context grammars, are used as a vehicle for knowledge representation in expert systems. Random context grammars and the manner in which they are used to represent knowledge are discussed. An example of a knowledge base is given.

1991-01-01T00:00:00Z Smith, THC Meyer, TWS Leenen, L https://ir.unisa.ac.za/handle/10500/23953 2018-05-20T01:00:46Z 1991-01-01T00:00:00Z

An efficient primal simplex implementation for the continuous 2-matching problem Smith, THC; Meyer, TWS; Leenen, L The continuous 2-matching problem {RMP2) is the relaxation of the symmetric travelling salesman problem {STSP) used by Padberg & Rinaldi to develop a highly successful branch-and-cut algorithm for the STSP. They used a standard linear program solver for solving RM P2. We note that RM P2 is a generalized network problem with additional special structure and exploit this to provide an efficient implementation of the primal simplex algorithm for RM P2. Our computational experience with the implementation demonstrates that it is several or­ders of magnitude faster than a standard linear program solver, suggesting that it should be worthwhile using this implementation in the Padberg-Rinaldi algorithm.

1991-01-01T00:00:00Z Shaw, V https://ir.unisa.ac.za/handle/10500/23952 2018-05-20T01:00:45Z 1991-01-01T00:00:00Z

An update on UNINET-ZA: The Southern African Academic and Research Network Shaw, V The UNINET Academic and Research Network is a collaborative project among Universities, Research Councils and the FRD for the development, implementation and promotion of an academic and research network of computers in southern Africa, where it is required as an essential element of the region's research infrastructure.

1991-01-01T00:00:00Z