Abstract: An improved method and system for visualizing an object-oriented program's execution in a manner that facilitates understanding, debugging, and tuning programs of arbitrary size and complexity by visually depicting a sequence of one or more messages to an object or between objects as a tree. Each node in the tree represents an object, and each edge represents a message between the objects. To manage the complexity of what is displayed, the user may elect to collapse subtrees so that they appear in abbreviated form. The user may expand collapsed subtrees so that they are visible in full. By selectively expanding and collapsing subtrees, the user can examine only those parts of the execution that are immediately relevant. The user may specify additional criteria for classifying subtrees, i.e., the conditions under which two subtrees are deemed equivalent. The system can then consolidate equivalent subtrees automatically, replacing them with a more general execution pattern that subsumes them all.

Abstract: An object oriented dispatch optimization method determines statically which body of code will be executed when a method is dispatched. The program code is examined to identify all procedure bodies that can be invoked for a given class and a given method. An identified procedure body is analyzed to determine whether a method invocation on a pointer can invoke only one procedure body. Based on this analysis, either the procedure body or the invocation mechanism is changed so a unique procedure is directly called without a test or dispatch being used.

Abstract: A simple approach to graph layout is fast and results in graphs that lend themselves to full visualization on a standard-sized computer monitor. The algorithm implemented allows the use the same spring and repulsion energies as in the force-directed model, or any other reasonably behaved energy function. In addition, numerical methods, either the technique of polynomial approximation or quadratic approximation, are applied. This allows approximating the minimum or maximum of a general function by picking a small set of points and computing the local optima of a polynomial function that passes through them. Polynomial or quadratic approximation is used to produce candidate drawings and, ultimately, to select a low-energy drawing from these candidates.

Abstract: In an information retrieval system, a query issued by the user is analyzed by a query engine into query elements. After the query has been evaluated against the document collections, a resulting hit list is presented to the user, e.g., as a table. The presented hit list displays not only an overall rank of a document but also a contribution of each query element to the rank of the document. The user can reorder the hit list by prioritizing the contribution of individual query elements to override the overall rank and by assigning additional weight(s) to those contributions.

Abstract: Communications between a Host Computing System and a number of remote terminals is enhanced by a data compression method which modifies the data compression method of Lempel and Ziv by addition of new character and new string extensions to improve the compression ratio, and deletion of a least recently used routine to limit the encoding tables to a fixed size to significantly improve data transmission efficiency.

Abstract: Elements x in a domain A are hashed into a range B by selecting any one of a plurality of hashing functions which collectively form an almost universal.sub.2 class of functions. The data element to be hashed is separated into individual sub-strings x.sub.1 through x.sub.n of no more than log.sub.2 (b) bits in length, where b is an integer, and the hashing algorithm is a polynomial of the form f.sub.y (x)=(y.sup.0 x.sub.1 +y.sup.1 x.sub.2 + . . . +y.sup.n-1 x.sub.n) (mod b). In general, for a finite field of b=p.sup.k elements, where k is a positive integer, there will be a hash function defined by the formula f.sub.y (x)=y.sup.0 x.sub.1 +y.sup.1 x.sub.2 + . . . +y.sup.n-1 x.sub.n, where the addition and multiplication operations are those defined by the finite field and y is an element of the field. In a second embodiment, the hashing is a two-stage process defined by g.sub.z (f.sub.y (x)), where f.sub.y (x) is defined as above and g.sub.z is a function selected from a known universal.sub.

Abstract: The invention comprises a method and apparatus for performing a hashing operation on an N bit number under control of a prespecified N bit hashing constant which comprises performing N/K finite field partial multiplications of the object to be hashed by the hashing constant, utilizing K logic and combinatorial circuits all of which operate in parallel to completely evaluate the number in N/K operations.Another feature of the present invention is that the hashing constant loaded into the system may be changed at will with a resultant changing of the hashing characteristics to suit a particular class of objects to be hashed. This is done by a "select" operation.