17147705
Distributed algorithms for the quickest path problem
Let N = (V, A, C, L) be a network with node set V, arc set A, positive arc capacity function C, and nonnegative arc lead time function L. The quickest path problems is to find paths in N to transmit a given amount of data such that the transmission time is minimized. In this paper, distributed algorithms are developed for the quickest path problem in an asynchronous communication network. For the one-source quickest path problem, we present three algorithms that require O(rn2) messages and O(2) time, O(n) messages and O(rn) time, and O1+elog w) messages and O(rn1+elog w) time for any e, 0<e<1, respectively, where m = |A|, n = |V|, r is the number of distinct capacity values of N, and w is the maxima arc weight of N. For the all-pairs quickest path problem, we present an algorithm that requires O(mn) messages and O(m) time.
6244297
A layered communication system generator
Abstract Although many approaches have been proposed for modeling and automatically validating communication protocol entities, no approaches have been proposed for automatically implementing various layered communication systems. In the article, we propose a layered communication system generator that can automatically implement various layered communication systems. The layered communication system generator is established on the basis of a generalized communication system framework. In addition, a layered communicating finite state machine is introduced to specify the layered communication systems, and a matrix approach is proposed for protocol validation. We have implemented the proposed layered communication system generator in DOS and UNIX environments, in which several real-world protocols from Department of Defense and IEEE 802 standards organizations have been successfully developed.
30765152
On the Quickest Path Problem
Abstract Let N be an input network and σ be the amount of data to be transmitted. We present an O( mn 2 ) time algorithm that finds all-pairs quickest paths, for a given value of σ, and show that the quickest path between any two nodes for any value of σ can be found in O(log m ) time, provided O( mn 2 ) preprocessing time is spent.
35779178
On the Quickest Path Problem
In this paper, we propose an O(mn2) time algorithm that finds all-pairs quickest paths in a given network N, where n and m are the numbers of nodes and arcs, respectively, in N. Besides, the quickest path between any two nodes can be determined in O(log m) time, provided O(mn2) time preprocessing is made.
24161285
Effects of Local-Lag Mechanism on Task Performance in a Desktop CVE System
Consistency maintenance is a kernel problem in Collaborative Virtual Environment (CVE) research. The approaches used in Networked Virtual Environments (e.g., DR algorithm) could not be used in CVEs, for they could not prevent short-term inconsistency. Therefore, local-lag mechanism has been proposed to eliminate short-term inconsistency in CVEs. Choosing a proper lag value is a key problem in local-lag mechanism. This paper studied the effects of lag value (0ms–900ms) on task performance in a desktop CVE system. Experimental results indicate that the effect of lag value on task performance is not linear. The effect could be separated into four segments by three dividing points: 150ms, 300ms and 600ms. Lag has no effect on task performance while ranging from 0ms to 150ms. From 150ms to 300ms, lag slightly affects task performance. Lag deteriorates task performance seriously while ranging from 300ms to 600ms. When lag is longer than 600ms, the task cannot be accomplished sometimes.
42359427
Subtyping Calculus of Construction (Extended Abstract)
We present in this paper a subtyping extension of Calculus of Construction. We prove that this system has good meta-theoretical properties: transitivity elimination, subject reduction, strong normalization and decidability of subtyping. This work provides a theoretical foundation for adding subtyping to proof checkers like Coq, LEGO etc.
1160338
Graph Connectivity After Path
Removal
Let G be a graph and
u, v be two distinct vertices of
G. A u—v path P is called nonseparating if
G—V(P) is connected. The purpose of this
paper is to study the number of nonseparating
u—v path for two arbitrary
vertices u and
v of a given graph. For a
positive integer k, we will
show that there is a minimum integer α(k) so that if G is an α(k)-connected graph and
u and v are two arbitrary vertices in
G, then there exist
k vertex disjoint paths
P1[u,v], P2[u,v], . . ., Pk[u,v], such that G—V (Pi[u,v]) is connected for every
i (i = 1, 2, ..., k). In fact, we will prove that
α(k) ≤ 22k+2. It is known that α(1) = 3.. A
result of Tutte showed that α(2) = 3. We show that α(3) = 6. In
addition, we prove that if G
is a 5-connected graph, then for every pair of vertices
u and v there exists a path
P[u, v] such that G—V(P[u,
v]) is 2-connected.
17483991
Energy-aware computation duplication for improving reliability in embedded chip multiprocessors
Compilers designed for current embedded systems must be capable of addressing multiple constraints such as low power, high performance, small memory footprint and form factor, and high reliability at the same time. In particular, optimizing for one constraint should be performed carefully, considering its impact on other constraints. Recent trends indicate that transient errors are becoming increasingly important in embedded systems. Focusing on an embedded chip multiprocessor and array-intensive applications, this paper demonstrates how reliability against transient errors can be improved without impacting execution time by utilizing idle processors for duplicating some of the computations of the active processors. It also shows how a balance between power savings and reliability improvement can be struck using a metric called the energy-delay-fallibility product. Our experimental results indicate that the "percentage of duplicated computations" is a useful high-level metric for studying the tradeoffs among performance, power, and reliability
40869256
Parallel algorithms for permutation graphs
In this paper, parallel algorithms are presented for solving some problems on permutation graphs. The coloring problem is solved inO(log2n) time usingO(n3/logn) processors on the CREW PRAM, orO(logn) time usingO(n3) processors on the CRCW PRAM. The weighted clique problem, the weighted independent set problem, the cliques cover problem, and the maximal layers problem are all solved with the same complexities. We can also show that the longest common subsequence problem belongs to the class NC.