Tom Payne

Sorting X + Y

This paper consists of the application of well- known results to a new problem. The problem, posed by E. Berlekamp, was to save computation time in sorting sets of numbers of the form X q- Y. The main appeal of the new results, aside from their practical uses, is the diversity of the old ideas behind them. It is also interesting to see how the modeling of data and computing affect the results: when the model is of sorting n-tupules of real numbers with binary compari- sons, the best result we can do is nalogan comparisons, which is shown to be sharp under certain circumstances; when the model is of sorting n-tuples of integers in the range 0 to n -- 1, on a random-access stored program computer, the time complexity is shown to be on the order of n(logan).

What do students know?: an outcomes-based assessment system

Well-run organizations collect, archive and analyze data relating to the effectiveness of their important processes. Educational institutions discard a wealth of student scores that could be analyzed. Each score contains important information about the student as well as the item (i.e., problem or question). This paper describes our project to develop an outcomes-based assessment system that mines per-item scores to track each students skills and knowledge. Statistical inference techniques from both educational statistics and data mining will quantitatively determine each students acquired competency, with minimal input from faculty. The culmination of item-level assessment gives individual faculty feedback on their courses, and gives curriculum committees feedback on which objectives are sufficiently met by their respective curricula.

Graph allocation in static dataflow systems

One of the most important considerations for a dataflow multiprocessor is the algorithm by which the nodes of a program graph are allocated for execution to its processors. In the case of the static type of architecture one must consider pipelining as well as spatial concurrency. This paper uses a graph partitioning scheme to aid in the design of such algorithms and selection of the associated interconnection topology. The scheme first refines the usual dataflow program graph and then partitions it into “trees.” Our study shows that the hypercube interconnection accommodates these trees in a way that allows as to develop an algorithm that places producer nodes (of a dataflow graph) nears their consumers to keep the message path very short. The algorithm achieves concurrency in simultaneous execution of subgraphs that involve parallel operations, e.g., array operations, and subgraphs that are highly iterative or recursive. An analytical model is given to evaluate the performance of the algorithm.

Parallel sorting in a ring network of processors

A parallel implementation of selection sorting algorithms is presented that uses a ring-connected array of processors, in which each processor has the same amount of memory. The scheme allows all processors to have the same amount of memory with a small fragmentation loss. Uniformity in the size of the memories provides advantages from the viewpoint of manufacture, maintenance, inventory, item placement, and many other aspects of system design. These memories can, together, function as an interleaved memory for a general-purpose computer. Hence, it is possible to build a medium-scale system in which parallel-sort is implemented as a primitive, like block-move, without a large increment in hardware complexity and cost. An analysis is presented that shows how to improve performance by overlapping comparisons with memory accesses and how to achieve performance improvement by applying carry-look-ahead techniques to comparison. >

Computer aided assessment with human oversight

For nearly fifty years, Computer Aided Assessment (CAA) in Computer Science has focused on the automated grading of programming assignments. Agar is a CAA framework that allows for automated grading of assignments, as well as efficient and effective human grading of subjective matters such as writing and code style. Agar features a system for reusable comments, which allows standard feedback and penalties to be assigned for a given error. The first time a given error is encountered, the grader writes out the comment and assigns it a penalty, and can simply select the comment and penalty from a list when the error is seen again. This approach reduces the amount of time require to grade, improves the uniformity of grading, and improves the quality of feedback to the students.to give quality feedback.