36 research outputs found
Detailed Modeling and Reliability Analysis of Fault-Tolerant Processor Arrays
Recent advances in VLSI/WSI technology have led to the design of processor arrays with a large number of processing elements confined in small areas. The use of redundancy to increase fault-tolerance has the effect of reducing the ratio of area dedicated to processing elements over the area occupied by other resources in the array. The assumption of fault-free hardware support (switches, buses, interconnection links, etc.,), leads at best to conservative reliability estimates. However, detailed modeling entails not only an explosive growth in the model state space but also a difficult model construction process. To address the latter problem, a systematic method to construct Markov models for the reliability evaluation of processor arrays is proposed. This method is based on the premise that the fault behavior of a processor array can be modeled by a Stochastic Petri Net (SPN). However, in order to obtain a more compact representation, a set of attributes is associated with each transition in the Petri net model. This representation is referred to as a Modified Stochastic Petri Net (MSPN) model. A MSPN allows the construction of the corresponding Markov model as the reachability graph is being generated. The Markov model generated can include the effect of failures of several different components of the array as well as the effect of a peculiar distribution of faults when the reconfiguration occurs. Specific reconfiguration schemes such as Successive Row Elimination (SRE), Alternate Row-Column Elimination (ARCE) and Direct Reconfiguration (DR), are analyze
COSMIC: A Model for Multiprocessor Performance Analysis
COSMIC, the Combined Ordering Scheme Model with Isolated Components, describes the execution of specific algorithms on multiprocessors and facilitates analysis of their performance. Building upon previous modeling efforts such as Petri nets, COSMIC structures the modeling of a system along several issues including computational and overhead costs due to sequencing of operations, synchronization between operations, and contention for limited resources. This structuring allows us to isolate the performance impact associated with each issue. Finally, studying the performance of a system while executing a specific algorithm gives insight into its performance under realistic operating conditions. The model also allows us to study realistically sized algorithms with ease, especially when they are regularly structured. During the analysis of a system modeled by COSMIC, a set timed Petri nets is produced. These Petri nets are then analyzed to determine measures of the systems performance. To facilitate the specification, manipulation, and analysis of large timed Petri nets, a set of tools has been developed. These tools take advantage of several special properties of the timed Petri nets that greatly reduce the computational resources required to calculate the required measures. From this analysis, performance measures show not only total performance, but also present a breakdown of these results into several specific categories
Archer: A Community Distributed Computing Infrastructure for Computer Architecture Research and Education
This paper introduces Archer, a community-based computing resource for
computer architecture research and education. The Archer infrastructure
integrates virtualization and batch scheduling middleware to deliver
high-throughput computing resources aggregated from resources distributed
across wide-area networks and owned by different participating entities in a
seamless manner. The paper discusses the motivations leading to the design of
Archer, describes its core middleware components, and presents an analysis of
the functionality and performance of a prototype wide-area deployment running a
representative computer architecture simulation workload.Comment: 11 pages, 2 figures. Describes the Archer project,
http://archer-project.or
Down-Regulation of hsa-miR-10a in Chronic Myeloid Leukemia CD34+ Cells Increases USF2-Mediated Cell Growth
MicroRNAs (miRNA) are small noncoding,
single-stranded RNAs that inhibit gene expression at a
posttranscriptional level, whose abnormal expression
has been described in different tumors. The aim of our
study was to identify miRNAs potentially implicated
in chronic myeloid leukemia (CML). We detected an
abnormal miRNA expression profile in mononuclear and
CD34+ cells from patients with CML compared with
healthy controls. Of 157 miRNAs tested, hsa-miR-10a,
hsa-miR-150, and hsa-miR-151 were down-regulated,
whereas hsa-miR-96 was up-regulated in CML cells.
Down-regulation of hsa-miR-10a was not dependent
on BCR-ABL1 activity and contributed to the increased
cell growth of CML cells. We identified the upstream
stimulatory factor 2 (USF2) as a potential target of
hsa-miR-10a and showed that overexpression of USF2
also increases cell growth. The clinical relevance of
these findings was shown in a group of 85 newly
diagnosed patients with CML in which expression of
hsa-miR-10a was down-regulated in 71% of the patients,
whereas expression of USF2 was up-regulated in 60% of
the CML patients, with overexpression of USF2 being
significantly associated with decreased expression of
hsa-miR-10a (P = 0.004). Our results indicate that
down-regulation of hsa-miR-10a may increase USF2 and
contribute to the increase in cell proliferation of CML
implicating a miRNA in the abnormal behavior of CML
On a Quantitative Model of Dynamic System Reconfiguration Due to a Fault
The use of dynamic reconfiguration has been proposed to tolerate faults in large-scale partitionable parallel processing systems. If a processor develops a permanent fault during the execution of a task on a submachine A, three recovery options are migration of the task to another submachine, task migration to a subdivision of A, and redistribution of the task among the fault-free processors in A. Quantitative models of these reconfiguration schemes are developed to consider what information is needed to make a choice among these methods for a practical implementation. It is pointed out that in certain situations collecting precise values for all needed parameters is very difficult. Therefore, the model parameters are then analyzed, together with the cost of making the wrong reconfiguration choice, to determine a useful heuristic that is based on the information available. A multistage cube or hypercube inter-processor network is assumed. PASM, an experimental SIMD/MIMD mixed-mode machine with a partitionable multistage cube communication network, and nCUBE 2, a commercially available MIMD machine with a partitionable hypercube communication network, are used as vehicles for studying the model parameters