V. Rajaraman – Communications of the ACM

Research and Advances Jul 1 1982

Searching in a dynamic memory with fast sequential access

This communication presents an algorithm for searching in the Aho-Ullman dynamic memory consisting of (2m - 1) cells. Mean search time of 1.5m steps to the first specified record is obtained with a subsequent sequential access capability. Thus, in such a dynamic memory, the mean access time for content addressing is the same as the mean access time for random addressing.

Architecture and Hardware

Author Archives

Research and Advances Dec 1 1978

Detection of logical errors in decision table programs

In this paper an algorithm to detect logical errors in a limited-entry decision table and in loop-free programs with embedded decision tables is developed. All the conditions in the decision tables are assumed to be inequalities or equalities relating linear expressions. It is also assumed that actions in a decision table are linear in variables which occur in the condition stub of the decision table (or tables) to which control is transferred from the table. The algorithm is based on determining whether a set of linear inequalities has or does not have a solution. The algorithm described in the paper is implemented in Fortran IV.

Computing Applications

Research and Advances Sep 1 1973

Information theory applied to the conversion of decision tables to computer programs

Using ideas from information theory, this paper develops a heuristic algorithm that converts a limited entry decision table to a tree structured computer program with near minimum average processing time. The method is applicable to any limited entry decision table and does not require that actions have single rules or that the cost of testing conditions be equal. It is thus more general than the previously published heuristic algorithms. Compared to the optimal algorithm of Reinwald and Soland, this algorithm is easy to code and takes a much smaller translation time; it is thus felt that it is more useful in practice. The algorithm is well suited for manual conversion of decision tables to flowcharts.

Research and Advances Jun 1 1970

On the conversion of decision tables to computer programs

The use of execution time diagnostics in pinpointing ambiguities in decision tables is discussed. It is pointed out that any attempt at resolving ambiguities at compile time will, in general, be impossible. It is shown that, as a consequence, tree methods of converting decision tables to programs are inadequate in regard to ambiguity detection. Two algorithms for programming decision tables whose merits are simplicity of implementation and detection of ambiguities at execution time are presented. The first algorithm is for limited entry decision tables and clarifies the importance of proper coding of the information in the decision table. The second algorithm programs a mixed entry decision table directly without going through the intermediate step of conversion to a limited entry form, thereby resulting in storage economy. A comparison of the algorithms and others proposed in the literature is made. Some features of a decision table to FORTRAN IV translator for the IBM 7044 developed by the authors are given.

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