5415824
Shared memory programming for large scale machines
This paper describes the design and implementation of a scalable run-time system and an optimizing compiler for Unified Parallel C (UPC). An experimental evaluation on BlueGene/L®, a distributed-memory machine, demonstrates that the combination of the compiler with the runtime system produces programs with performance comparable to that of efficient MPI programs and good performance scalability up to hundreds of thousands of processors.Our runtime system design solves the problem of maintaining shared object consistency efficiently in a distributed memory machine. Our compiler infrastructure simplifies the code generated for parallel loops in UPC through the elimination of affinity tests, eliminates several levels of indirection for accesses to segments of shared arrays that the compiler can prove to be local, and implements remote update operations through a lower-cost asynchronous message. The performance evaluation uses three well-known benchmarks --- HPC RandomAccess, HPC STREAM and NAS CG --- to obtain scaling and absolute performance numbers for these benchmarks on up to 131072 processors, the full BlueGene/L machine. These results were used to win the HPC Challenge Competition at SC05 in Seattle WA, demonstrating that PGAS languages support both productivity and performance.
38543445
3-D maximum likelihood reconstructions of viruses from cryo electron microscope images and parallel computation
A statistical method for computing 3-D reconstructions of virus particles from cryo electron microscope images and minimal prior information - particle symmetry and radii - is described. Two different approaches for parallel implementation of the algorithm are described based on parallel processing of different images and based on parallel numerical integration and numerical results showing nearly linear speedup are presented.
2310959
XKvalidator: a constraint validator for XML
The role of XML in data exchange is evolving from one of merely conveying the structure of data to one that also conveys its semantics. In particular, several proposals for key and foreign key constraints have recently appeared, and aspects of these proposals have been adopted within XMLSchema.In this paper, we examine the problem of checking keys and foreign keys in XML documents using a validator based on SAX. The algorithm relies on an indexing technique based on the paths found in key definitions, and can be used for checking the correctness of an entire document (bulk checking) as well as for checking updates as they are made to the document (incremental checking). The asymptotic performance of the algorithm is linear in the size of the document or update. Furthermore, experimental results demonstrate reasonable performance.
10569326
Intelligent compliant motion control
The role of a compliant motion scheme is to control a robot manipulator in contact with its environment. By accommodating with the interaction force, the manipulator can be used to accomplish tasks that involve constrained motions. This paper presents a new work on the compliant motion control for position-controlled manipulator. A new method for achieving efficient interaction between the manipulator and its environment is developed. The interaction force is reduced using a quadratic cost function. In this method, the compliance is formulated as function of the interaction force. An adaptive element is used to update the compliance. The stability of the system is investigated using the Lyapunov approach. Experiments are conducted in our laboratory to demonstrate the use of such scheme.
129842
BLAS: an efficient XPath processing system
We present BLAS, a Bi-LAbeling based System, for efficiently processing complex XPath queries over XML data. BLAS uses P-labeling to process queries involving consecutive child axes, and D-labeling to process queries involving descendant axes traversal. The XML data is stored in labeled form, and indexed to optimize descendent axis traversals. Three algorithms are presented for translating complex XPath queries to SQL expressions, and two alternate query engines are provided. Experimental results demonstrate that the BLAS system has a substantial performance improvement compared to traditional XPath processing using D-labeling.
15616759
A Method to Implement a Denial of Service Protection Base
Denial of service attack is an attempt from any authorized or unauthorized entity to allocate resources excessively to prevent normal operation of the system. A method will be presented to specify and enforce a resource allocation policy to prevent denial of service attacks. Resource allocation policy can be formally derived from a waiting time policy where maximum acceptable response times for different processes are specified.
13563503
A testbed for quantitative assessment of intrusion detection systems using fuzzy logic
The current intrusion detection system (IDS) technology is a major investment for a firm and its evaluation is desired prior to a commitment. A testbed compares different IDSs on a common platform. A major challenge in evaluating IDSs stems from the fact that they are generally tested in specific environments. A real-world environment could be different from the environment designed for a testbed. The results obtained, from such testbeds, may not be accurate and reliable. Hence, a quantitative and metrics based evaluation of IDSs is desired. We propose testbed for evaluating intrusion detection systems (TIDeS), that allows a user to select the best IDS for a specific customized environment. A quantitative analysis is provided by TIDeS, using fuzzy logic, under varying network loads. We also propose robust metrics to evaluate an IDS. We follow up with recommendations, based on our experience, on the general practices in the field of IDSs.