852380
Switching classes of directed graphs
By analogy with Seidel switching classes of graphs, and two-graphs, this paper develops a theory of switching classes of directed graphs. The elements of the theory are these: there is a one-to-one correspondence among switching classes of directed graphs, two-digraphs, and cyclic triple covers of the complete digraph. If G is a group of automorphisms of a switching class of digraphs, there is a cohomological invariant γ which vanishes if and only if some digraph in the switching class is fixed by G. If G is cyclic then γ ≠ 0 if and only if all orbits on vertices have size divisible by 3 and a certain sum (defined in Theorem 3.5) is nonzero. There is a second cohomological invariant β which vanishes if and only if G can be realized as a group of automorphisms of the cyclic triple cover associated with the switching class. If G is cyclic, then β ≠ 0 if and only if G has a subgroup of order 3 for which γ ≠ 0. There is a formula for the number of isomorphism types of two-digraphs on n vertices which is a sum over the symmetric group Sn of a simple function of the cycle structure of its elements. Finally, the only elements of Sn which fix a digraph in every switching class of digraphs they fix are those elements containing a cycle whose length is not divisible by 3.
40703514
On weakly symmetric graphs of order twice a prime
Abstract A graph is weakly symmetric if its automorphism group is both vertex-transitive and edge-transitive. In 1971, Chao characterized all weakly symmetric graphs of prime order and showed that such graphs are also transitive on directed edges. In this paper we determine all weakly symmetric graphs of order twice a prime and show that these graphs too are directed-edge transitive.
44320241
Convergence and Ordering of Kohonen's Batch Map
The convergence and ordering of Kohonen's batch-mode self-organizing map with Heskes and Kappen's (1993) winner selection are proved. Selim and Ismail's (1984) objective function for k-means clustering is generalized in the convergence proof of the self-organizing map. It is shown that when the neighborhood relation is doubly decreasing, order in the map is preserved. An unordered map becomes ordered when a degenerate state of ordering is entered, where the number of distinct winners is one or two. One strategy to enter this state is to run the algorithm with a broad neighborhood relation.
6228406
Distributed and parallel execution of Java programs on a DSM system
The paper focuses on the loop-level parallelism of bytecode on a distributed shared memory (DSM) system, which is built on a cluster of multiprocessors. We define a new attribute called 'Loop Attribute' to record the information of Java loops. When first loading a Java program, our Java virtual machine, called ES-JVM, checks and analyzes the loops of the bytecode dynamically, handles the data dependence of loops, and records the information as the loop attributes. ES-JVM uses the virtual shared memory and synchronization mechanisms provided by the DSM system to maintain the memory consistency. Before ES-JVM interprets the loops of the bytecodes, it dispatches the workload of loops to the interpreter threads at all nodes according to the loop attributes and the number of threads. After distributed and parallel execution of the loops, ES-JVM continues to interpret the rest of the bytecodes of the Java program. Finally, ES-JVM saves the loop attributes in a new class file for the next run. Our research shows that distributed and parallel execution of loops of a Java program could improve performance.
11793175
Internet Traffic Characterization Using Packet-Pair Probing
This paper presents an edge-based Internet traffic characterization approach. Our objective is to estimate the marginal distribution and the correlation structure of the packet arrival process at a queue, by sending probe packet pairs with a specific dispersion to sample the traffic. The aggregate work load process inferred from the output dispersions is a compound process of the packet arrival process and the packet size distribution. We show that the packet arrival marginal distribution and the packet size distribution can be decoupled by using the probability generating function; given one of the distributions, the other can then be estimated. We use the fact that the Internet packet size follows a known multi-modal distribution. Moreover, multiple series of packet pairs with different input dispersions can be used to estimate the packet arrival process at different time scales, and therefore to estimate the Hurst parameter, which characterizes the long-range dependence, by generating the variance-time plot. While the traffic characterization techniques are developed and validated in a single-queue context, we indicate how the techniques can be applied to a black box system for end-to-end quality of service provisioning along a multi-hop path.
1895998
A study of associative evidential reasoning
Evidential reasoning is cast as the problem of simplifying the evidence-hypothesis relation and constructing combination formulas that possess certain testable properties. Important classes of evidence as Identifiers, annihilators, and idempotents and their roles in determining binary operations on intervals of reals are discussed. The appropriate way of constructing formulas for combining evidence and their limitations, for instance, in robustness, are presented.
34097069
Building shallow expert systems using back-propagation learning