66 research outputs found
On the Connection Assignment Problem of Diagnosable Systems
Coordinated Science Laboratory was formerly known as Control Systems LaboratoryJoint Services Electronics Program / DA 28 043 AMC 00073(E)National Science Foundation / GK-690 and GK-3
Quantifying fault recovery in multiprocessor systems
Various aspects of reliable computing are formalized and quantified with emphasis on efficient fault recovery. The mathematical model which proves to be most appropriate is provided by the theory of graphs. New measures for fault recovery are developed and the value of elements of the fault recovery vector are observed to depend not only on the computation graph H and the architecture graph G, but also on the specific location of a fault. In the examples, a hypercube is chosen as a representative of parallel computer architecture, and a pipeline as a typical configuration for program execution. Dependability qualities of such a system is defined with or without a fault. These qualities are determined by the resiliency triple defined by three parameters: multiplicity, robustness, and configurability. Parameters for measuring the recovery effectiveness are also introduced in terms of distance, time, and the number of new, used, and moved nodes and edges
Testing the bus guardian unit of the FTMP
Fault-tolerant multiprocessor (FTMP) operation is discussed. Fault-modeling in the bus guardian units (BGUs) is covered. Testing the BGU is discussed. A testing algorithm is proposed
CONCURRENT DIAGNOSTICS IN MULTIPROCESSOR SYSTEMS
The paper presents a survey of diagnostic methods for multiprocessor systems. The diagnostic means known so far are first summarized and evaluated from the point of view of their applicability to systems with distributed control and specifically to the multiprocessor systems. A combination of different diagnostic means is then suggested in order to achieve the maximum diagnostic coverage with minimum overhead
Distributed Corruption Detection in Networks
We consider the problem of distributed corruption detection in networks. In
this model, each vertex of a directed graph is either truthful or corrupt. Each
vertex reports the type (truthful or corrupt) of each of its outneighbors. If
it is truthful, it reports the truth, whereas if it is corrupt, it reports
adversarially. This model, first considered by Preparata, Metze, and Chien in
1967, motivated by the desire to identify the faulty components of a digital
system by having the other components checking them, became known as the PMC
model. The main known results for this model characterize networks in which
\emph{all} corrupt (that is, faulty) vertices can be identified, when there is
a known upper bound on their number.
We are interested in networks in which the identity of a \emph{large
fraction} of the vertices can be identified.
It is known that in the PMC model, in order to identify all corrupt vertices
when their number is , all indegrees have to be at least . In contrast,
we show that in regular-graphs with strong expansion properties, a
fraction of the corrupt vertices, and a fraction of the
truthful vertices can be identified, whenever there is a majority of truthful
vertices. We also observe that if the graph is very far from being a good
expander, namely, if the deletion of a small set of vertices splits the graph
into small components, then no corruption detection is possible even if most of
the vertices are truthful. Finally, we discuss the algorithmic aspects and the
computational hardness of the problem
Computing Majority with Triple Queries
Consider a bin containing balls colored with two colors. In a -query,
balls are selected by a questioner and the oracle's reply is related
(depending on the computation model being considered) to the distribution of
colors of the balls in this -tuple; however, the oracle never reveals the
colors of the individual balls. Following a number of queries the questioner is
said to determine the majority color if it can output a ball of the majority
color if it exists, and can prove that there is no majority if it does not
exist. We investigate two computation models (depending on the type of replies
being allowed). We give algorithms to compute the minimum number of 3-queries
which are needed so that the questioner can determine the majority color and
provide tight and almost tight upper and lower bounds on the number of queries
needed in each case.Comment: 22 pages, 1 figure, conference version to appear in proceedings of
the 17th Annual International Computing and Combinatorics Conference (COCOON
2011
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