Summary
The problem of finding optimal cycles in a doubly weighted directed graph (Problem A) is closely related to the problem of approximating bivariate functions by the sum of two univariate functions with respect to the supremum norm (Problem B). The close relationship between Problem A and Problem B is detected by the characterization (7.4) of the distance dist (f, t) of Problem B.
In Part 1 we construct an algorithm for Problem A where the essential role is played by the minimal lengthsy j(k) defined by (2.3). If weight functiont≡1 then the minimum of Problem A is computed by equality (2.4). Ift≡1 then the minimum is obtained by a binary search procedure, Algorithm 3.
In Part 2 we construct our algorithms for solving Problem B by following exactly the ideas of Part 1. By Algorithm 4 we compute the minimal pseudolengthsh k(y, M) defined by (7.5). If weight functiont≡1 then the infimum dist(f,t) of Problem B is obtained by equality (7.12) which is closely related to (2.4). Ift≢1 we compute the infimum dist(f,t) by the binary search procedure Algorithm 5.
Additionally, Algorithm 4 leads to a constructive proof of the existence of continuous optimal solutions of Problem B (see Theorem 7.1e) which is already known in caset≡1 but unknown in caset≢1.
Interesting applications to the steady-state behaviour of industrial processes with interference (Sect. 3) and the solution of integral equations (Problem C) are included.
Similar content being viewed by others
References
Aumann, G.: Über approximative Nomographie, I und II. Bayer. Akad. Wiss. Math.-Natur Kl. S.B., 137–155 (1958), Ibid. Aumann, G.: Über approximative Nomographie, I und II. Bayer. Akad. Wiss. Math.-Natur Kl. S.B., 103–109 (1959)
Buck, R.C.: On approximation theory and functional equations. J. Approximation Theory5, 228–237 (1972)
Cheney, E.W., Golitschek, M. v.: On the algorithm of Diliberto and Straus for approximating bivariate functions by univariate ones. Numer. Funct. Anal. and Optimiz.I, 341–363 (1979)
Cheney, E.W., Light, W.A.: On the approximation of a bivariate function by the sum of univariate ones. J. Approximation Theory (to appear).
Cheney, E.W., Light, W.A.: Multivariate approximation with tensor-product spaces. Center for Numerical Analysis, University of Texas at Austin, Report CNA-153 (1979)
Collatz, L.: Approximation by functions of fewer variables. Conference on the theory of ordinary and partial differential equations. In: Lecture Notes in Math. 280, pp. 16–31 (W.N. Everitt and B.D. Sleeman, eds.). Dundee, Scotland, (1972)
Diliberto, S.P., Straus, E.G.: On the approximation of a function of several variables by the sum of functions of fewer variables. Pacific J. Math.1, 195–210 (1951)
v. Golitschek, M.: An algorithm for scaling matrices and computing the minimum cycle mean in a digraph. Numer. Math.35, 45–55 (1980)
Golomb, M.: Approximation by functions of fewer variables. In: Symposium on Numerical Approximation (R. Langer, ed.), pp. 275–327. University of Wisconsin Press. Madison, Wisconsin, (1959)
Havinson, S.J.: A Chebyshev theorem for the approximation of a function of two variables by sums ϕ(x)+ψ(y). Izv. Akad. Nauk SSSR Ser. Mat.33, 650–666 (1969)
Johnson, D.B.: Algorithms for shortest paths. Ph.D. Thesis, Cornell University, Ithaca, N.Y. (1973)
Karp, R.M.: A characterization of the minimum cycle mean in a digraph. Discrete Mathematics23, 309–311 (1978)
Lawler, E.L.: Optimal cycles in doubly weighted linear graphs. In: Theory of Graphs, (P. Rosenstiehl, ed.), pp. 209–214. Dunod, Paris and Gordon and Beach. New York 1967
Lawler, E.L.: In: Combinatorial optimization: Networks and Matroids. Holt, Rinehart and Winston. New York: 1976
Ofman, J.P.: Best approximation of functions of two variables by functions of the form ϕ(x)+ψ(y). Americ. Math. Soc. Transl.44, 12–29 (1965)
Tarjan, R.E.: Depth-first search and linear graph algorithms. SIAM J. Comput.1, 146–160 (1972)
Rivlin, T.J., Sibner, R.J.: The degree of approximation of certain functions of two variables by the sum of functions of one variable. Amer. Math. Monthly72, 1101–1103 (1965)
Sprecher, D.A.: On best approximations of functions of two variables. Duke Math. J.35, 391–397 (1968)
Cuninghame-Green, R.A.: Describing industrial processes with interference and approximating their steady-state behaviour. Operational Res. Quart.13, 95–100 (1962)
Author information
Authors and Affiliations
Additional information
Supported by Deutsche Forschungsgemeinschaft Grant No. GO 270/3
Rights and permissions
About this article
Cite this article
v. Golitschek, M. Optimal cycles in doubly weighted graphs and approximation of bivariate functions by univariate ones. Numer. Math. 39, 65–84 (1982). https://doi.org/10.1007/BF01399312
Received:
Issue Date:
DOI: https://doi.org/10.1007/BF01399312